path: root/test/test_relational_engine.ml

(** Tests for the relational engine *)

open Relational_engine

(* ============================================================================
   Merkle Tree Tests
   ============================================================================ *)

let%test_unit "merkle: empty tree" =
  let tree = Merkle.empty in
  assert (Merkle.is_empty tree);
  assert (Merkle.size tree = 0);
  assert (Merkle.root_hash tree = None)

let%test_unit "merkle: insert single element" =
  let tree = Merkle.empty in
  let hash = "abc123" in
  let tree = Merkle.insert hash tree in
  assert (not (Merkle.is_empty tree));
  assert (Merkle.size tree = 1);
  assert (Merkle.member hash tree);
  assert (Merkle.root_hash tree <> None)

let%test_unit "merkle: insert multiple elements" =
  let tree = Merkle.empty in
  let tree = Merkle.insert "hash1" tree in
  let tree = Merkle.insert "hash2" tree in
  let tree = Merkle.insert "hash3" tree in
  assert (Merkle.size tree = 3);
  assert (Merkle.member "hash1" tree);
  assert (Merkle.member "hash2" tree);
  assert (Merkle.member "hash3" tree);
  assert (not (Merkle.member "hash4" tree))

let%test_unit "merkle: delete element" =
  let tree = Merkle.empty in
  let tree = Merkle.insert "hash1" tree in
  let tree = Merkle.insert "hash2" tree in
  assert (Merkle.size tree = 2);
  let tree = Merkle.delete "hash1" tree in
  assert (Merkle.size tree = 1);
  assert (not (Merkle.member "hash1" tree));
  assert (Merkle.member "hash2" tree)

let%test_unit "merkle: keys returns all elements" =
  let tree = Merkle.empty in
  let tree = Merkle.insert "c" tree in
  let tree = Merkle.insert "a" tree in
  let tree = Merkle.insert "b" tree in
  let keys = Merkle.keys tree in
  assert (List.length keys = 3);
  assert (List.mem "a" keys);
  assert (List.mem "b" keys);
  assert (List.mem "c" keys)

let%test_unit "merkle: root hash changes on insert" =
  let tree = Merkle.empty in
  let tree1 = Merkle.insert "hash1" tree in
  let root1 = Merkle.root_hash tree1 in
  let tree2 = Merkle.insert "hash2" tree1 in
  let root2 = Merkle.root_hash tree2 in
  assert (root1 <> root2)

let%test_unit "merkle: same elements produce same root hash" =
  let tree1 = Merkle.empty
    |> Merkle.insert "a"
    |> Merkle.insert "b" in
  let tree2 = Merkle.empty
    |> Merkle.insert "b"
    |> Merkle.insert "a" in
  assert (Merkle.root_hash tree1 = Merkle.root_hash tree2)

(* ============================================================================
   Physical Storage Tests
   ============================================================================ *)

let%test_unit "storage: create and close" =
  match Management.Physical.Memory.create () with
  | Error _ -> assert false
  | Ok storage ->
    Management.Physical.Memory.close storage

let%test_unit "storage: store and load attribute" =
  match Management.Physical.Memory.create () with
  | Error _ -> assert false
  | Ok storage ->
    let value = Obj.magic 42 in
    (match Management.Physical.Memory.store_attribute storage value with
     | Error _ -> assert false
     | Ok hash ->
       (match Management.Physical.Memory.load_attribute storage hash with
        | Error _ -> assert false
        | Ok None -> assert false
        | Ok (Some loaded) ->
          assert ((Obj.magic loaded : int) = 42)));
    Management.Physical.Memory.close storage

let%test_unit "storage: store and load raw bytes" =
  match Management.Physical.Memory.create () with
  | Error _ -> assert false
  | Ok storage ->
    let hash = "test_hash" in
    let data = Bytes.of_string "hello world" in
    (match Management.Physical.Memory.store_raw storage hash data with
     | Error _ -> assert false
     | Ok () ->
       (match Management.Physical.Memory.load_raw storage hash with
        | Error _ -> assert false
        | Ok None -> assert false
        | Ok (Some loaded) ->
          assert (Bytes.equal loaded data)));
    Management.Physical.Memory.close storage

let%test_unit "storage: exists check" =
  match Management.Physical.Memory.create () with
  | Error _ -> assert false
  | Ok storage ->
    let hash = "exists_test" in
    let data = Bytes.of_string "data" in
    (match Management.Physical.Memory.exists storage hash with
     | Error _ -> assert false
     | Ok exists -> assert (not exists));
    (match Management.Physical.Memory.store_raw storage hash data with
     | Error _ -> assert false
     | Ok () ->
       (match Management.Physical.Memory.exists storage hash with
        | Error _ -> assert false
        | Ok exists -> assert exists));
    Management.Physical.Memory.close storage

let%test_unit "storage: transaction commit" =
  match Management.Physical.Memory.create () with
  | Error _ -> assert false
  | Ok storage ->
    let result = Management.Physical.Memory.with_transaction storage (fun () ->
      let hash = "tx_test" in
      let data = Bytes.of_string "tx_data" in
      Management.Physical.Memory.store_raw storage hash data
    ) in
    (match result with
     | Error _ -> assert false
     | Ok () ->
       (match Management.Physical.Memory.exists storage "tx_test" with
        | Error _ -> assert false
        | Ok exists -> assert exists));
    Management.Physical.Memory.close storage

(* ============================================================================
   Database Tests
   ============================================================================ *)

let%test_unit "database: create empty" =
  let db = Management.Database.empty ~name:"test_db" in
  assert (db.name = "test_db");
  assert (Merkle.is_empty db.tree);
  assert (Management.Database.RelationMap.is_empty db.relations);
  assert (db.history = [])

let%test_unit "database: add relation" =
  let db = Management.Database.empty ~name:"test_db" in
  (* Create a minimal relation for testing *)
  let relation = Relation.make
    ~hash:(Some "rel_hash_1")
    ~name:"users"
    ~schema:Schema.empty
    ~tree:(Some Merkle.empty)
    ~constraints:None
    ~cardinality:(Conventions.Cardinality.Finite 0)
    ~generator:None
    ~membership_criteria:(fun _ -> true)
    ~provenance:Relation.Provenance.Undefined
    ~lineage:(Relation.Lineage.Base "users")
  in
  let db = Management.Database.add_relation db ~relation in
  assert (Management.Database.has_relation db "users");
  assert (Management.Database.get_relation_hash db "users" = Some "rel_hash_1");
  assert (not (Management.Database.has_relation db "orders"))

let%test_unit "database: remove relation" =
  let db = Management.Database.empty ~name:"test_db" in
  let relation = Relation.make
    ~hash:(Some "hash1")
    ~name:"users"
    ~schema:Schema.empty
    ~tree:(Some Merkle.empty)
    ~constraints:None
    ~cardinality:(Conventions.Cardinality.Finite 0)
    ~generator:None
    ~membership_criteria:(fun _ -> true)
    ~provenance:Relation.Provenance.Undefined
    ~lineage:(Relation.Lineage.Base "users")
  in
  let db = Management.Database.add_relation db ~relation in
  assert (Management.Database.has_relation db "users");
  let db = Management.Database.remove_relation db ~name:"users" in
  assert (not (Management.Database.has_relation db "users"))

let%test_unit "database: update relation" =
  let db = Management.Database.empty ~name:"test_db" in
  let relation = Relation.make
    ~hash:(Some "hash1")
    ~name:"users"
    ~schema:Schema.empty
    ~tree:(Some Merkle.empty)
    ~constraints:None
    ~cardinality:(Conventions.Cardinality.Finite 0)
    ~generator:None
    ~membership_criteria:(fun _ -> true)
    ~provenance:Relation.Provenance.Undefined
    ~lineage:(Relation.Lineage.Base "users")
  in
  let db = Management.Database.add_relation db ~relation in
  let old_db_hash = db.hash in
  let updated_relation = { relation with hash = Some "hash2" } in
  let db = Management.Database.update_relation db ~relation:updated_relation in
  assert (Management.Database.get_relation_hash db "users" = Some "hash2");
  assert (db.hash <> old_db_hash);
  assert (List.mem old_db_hash db.history)

let%test_unit "database: get relation names" =
  let db = Management.Database.empty ~name:"test_db" in
  let rel1 = Relation.make
    ~hash:(Some "h1")
    ~name:"users"
    ~schema:Schema.empty
    ~tree:(Some Merkle.empty)
    ~constraints:None
    ~cardinality:(Conventions.Cardinality.Finite 0)
    ~generator:None
    ~membership_criteria:(fun _ -> true)
    ~provenance:Relation.Provenance.Undefined
    ~lineage:(Relation.Lineage.Base "users")
  in
  let rel2 = Relation.make
    ~hash:(Some "h2")
    ~name:"orders"
    ~schema:Schema.empty
    ~tree:(Some Merkle.empty)
    ~constraints:None
    ~cardinality:(Conventions.Cardinality.Finite 0)
    ~generator:None
    ~membership_criteria:(fun _ -> true)
    ~provenance:Relation.Provenance.Undefined
    ~lineage:(Relation.Lineage.Base "orders")
  in
  let db = Management.Database.add_relation db ~relation:rel1 in
  let db = Management.Database.add_relation db ~relation:rel2 in
  let names = Management.Database.get_relation_names db in
  assert (List.length names = 2);
  assert (List.mem "users" names);
  assert (List.mem "orders" names)

(* ============================================================================
   Manipulation Tests (using Memory storage)
   ============================================================================ *)

(* Helper to create storage for tests *)
let with_storage f =
  match Management.Physical.Memory.create () with
  | Error _ -> assert false
  | Ok storage ->
    let result = f storage in
    Management.Physical.Memory.close storage;
    result

let%test_unit "manipulation: create database" =
  with_storage (fun storage ->
    match Manipulation.Memory.create_database storage ~name:"my_db" with
    | Error _ -> assert false
    | Ok db -> assert (db.name = "my_db"))

let%test_unit "manipulation: create relation" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty
      |> Schema.add "name" "string"
      |> Schema.add "age" "integer" in
    match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
    | Error _ -> assert false
    | Ok (db, relation) ->
      assert (relation.name = "users");
      assert (relation.schema = schema);
      assert (Management.Database.has_relation db "users"))

let%test_unit "manipulation: create relation already exists" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty in
    match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
    | Error _ -> assert false
    | Ok (db, _) ->
      match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
      | Error (Manipulation.RelationAlreadyExists _) -> ()
      | _ -> assert false)

let%test_unit "manipulation: retract relation" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty in
    match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
    | Error _ -> assert false
    | Ok (db, _) ->
      assert (Management.Database.has_relation db "users");
      match Manipulation.Memory.retract_relation storage db ~name:"users" with
      | Error _ -> assert false
      | Ok db ->
        assert (not (Management.Database.has_relation db "users")))

let%test_unit "manipulation: create tuple with storage" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty
      |> Schema.add "name" "string" in
    match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
    | Error _ -> assert false
    | Ok (db, relation) ->
      let attrs = Tuple.AttributeMap.empty
        |> Tuple.AttributeMap.add "name" { Attribute.value = Obj.magic "Alice" } in
      let tuple : Tuple.materialized = { relation = "users"; attributes = attrs } in
      match Manipulation.Memory.create_tuple storage db relation tuple with
      | Error _ -> assert false
      | Ok (_db, new_relation, _hash) ->
        assert (Manipulation.Memory.tuple_count new_relation = 1))

let%test_unit "manipulation: create and load tuple" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty
      |> Schema.add "value" "integer" in
    match Manipulation.Memory.create_relation storage db ~name:"numbers" ~schema with
    | Error _ -> assert false
    | Ok (db, relation) ->
      let attrs = Tuple.AttributeMap.empty
        |> Tuple.AttributeMap.add "value" { Attribute.value = Obj.magic 42 } in
      let tuple : Tuple.materialized = { relation = "numbers"; attributes = attrs } in
      match Manipulation.Memory.create_tuple storage db relation tuple with
      | Error _ -> assert false
      | Ok (_db, _relation, tuple_hash) ->
        (* Now load the tuple back from storage *)
        match Manipulation.Memory.load_tuple storage tuple_hash with
        | Error _ -> assert false
        | Ok None -> assert false
        | Ok (Some loaded_tuple) ->
          assert (loaded_tuple.relation = "numbers");
          let loaded_value = Tuple.AttributeMap.find "value" loaded_tuple.attributes in
          assert ((Obj.magic loaded_value.Attribute.value : int) = 42))

let%test_unit "manipulation: create multiple tuples with storage" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty
      |> Schema.add "id" "integer" in
    match Manipulation.Memory.create_relation storage db ~name:"items" ~schema with
    | Error _ -> assert false
    | Ok (db, relation) ->
      let make_tuple id =
        let attrs = Tuple.AttributeMap.empty
          |> Tuple.AttributeMap.add "id" { Attribute.value = Obj.magic id } in
        ({ Tuple.relation = "items"; attributes = attrs } : Tuple.materialized)
      in
      let tuples = [make_tuple 1; make_tuple 2; make_tuple 3] in
      match Manipulation.Memory.create_tuples storage db relation tuples with
      | Error _ -> assert false
      | Ok (_db, new_relation, hashes) ->
        assert (Manipulation.Memory.tuple_count new_relation = 3);
        assert (List.length hashes = 3))

let%test_unit "manipulation: load multiple tuples" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty
      |> Schema.add "n" "integer" in
    match Manipulation.Memory.create_relation storage db ~name:"test" ~schema with
    | Error _ -> assert false
    | Ok (db, relation) ->
      let make_tuple n =
        let attrs = Tuple.AttributeMap.empty
          |> Tuple.AttributeMap.add "n" { Attribute.value = Obj.magic n } in
        ({ Tuple.relation = "test"; attributes = attrs } : Tuple.materialized)
      in
      match Manipulation.Memory.create_tuples storage db relation [make_tuple 10; make_tuple 20] with
      | Error _ -> assert false
      | Ok (_db, _relation, hashes) ->
        match Manipulation.Memory.load_tuples storage hashes with
        | Error _ -> assert false
        | Ok loaded ->
          assert (List.length loaded = 2);
          let values = List.map (fun t ->
            let attr = Tuple.AttributeMap.find "n" t.Tuple.attributes in
            (Obj.magic attr.Attribute.value : int)
          ) loaded in
          assert (List.mem 10 values);
          assert (List.mem 20 values))

let%test_unit "manipulation: retract tuple" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty
      |> Schema.add "value" "integer" in
    match Manipulation.Memory.create_relation storage db ~name:"numbers" ~schema with
    | Error _ -> assert false
    | Ok (db, relation) ->
      let attrs = Tuple.AttributeMap.empty
        |> Tuple.AttributeMap.add "value" { Attribute.value = Obj.magic 42 } in
      let tuple : Tuple.materialized = { relation = "numbers"; attributes = attrs } in
      match Manipulation.Memory.create_tuple storage db relation tuple with
      | Error _ -> assert false
      | Ok (db, relation, tuple_hash) ->
        assert (Manipulation.Memory.tuple_count relation = 1);
        match Manipulation.Memory.retract_tuple storage db relation ~tuple_hash with
        | Error _ -> assert false
        | Ok (_db, relation) ->
          assert (Manipulation.Memory.tuple_count relation = 0);
          (* Tuple data still exists in storage (append-only) *)
          match Manipulation.Memory.load_tuple storage tuple_hash with
          | Error _ -> assert false
          | Ok None -> assert false
          | Ok (Some _) -> () (* Data is still there *))

let%test_unit "manipulation: tuple hashes" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty in
    match Manipulation.Memory.create_relation storage db ~name:"test" ~schema with
    | Error _ -> assert false
    | Ok (db, relation) ->
      let make_tuple n =
        let attrs = Tuple.AttributeMap.empty
          |> Tuple.AttributeMap.add "n" { Attribute.value = Obj.magic n } in
        ({ Tuple.relation = "test"; attributes = attrs } : Tuple.materialized)
      in
      match Manipulation.Memory.create_tuples storage db relation [make_tuple 1; make_tuple 2] with
      | Error _ -> assert false
      | Ok (_db, relation, _) ->
        let hashes = Manipulation.Memory.tuple_hashes relation in
        assert (List.length hashes = 2))

let%test_unit "manipulation: clear relation" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty in
    match Manipulation.Memory.create_relation storage db ~name:"test" ~schema with
    | Error _ -> assert false
    | Ok (db, relation) ->
      let make_tuple n =
        let attrs = Tuple.AttributeMap.empty
          |> Tuple.AttributeMap.add "n" { Attribute.value = Obj.magic n } in
        ({ Tuple.relation = "test"; attributes = attrs } : Tuple.materialized)
      in
      match Manipulation.Memory.create_tuples storage db relation [make_tuple 1; make_tuple 2; make_tuple 3] with
      | Error _ -> assert false
      | Ok (db, relation, _) ->
        assert (Manipulation.Memory.tuple_count relation = 3);
        match Manipulation.Memory.clear_relation storage db relation with
        | Error _ -> assert false
        | Ok (_db, relation) ->
          assert (Manipulation.Memory.tuple_count relation = 0))

let%test_unit "manipulation: duplicate tuple rejected" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty
      |> Schema.add "x" "integer" in
    match Manipulation.Memory.create_relation storage db ~name:"test" ~schema with
    | Error _ -> assert false
    | Ok (db, relation) ->
      let attrs = Tuple.AttributeMap.empty
        |> Tuple.AttributeMap.add "x" { Attribute.value = Obj.magic 1 } in
      let tuple : Tuple.materialized = { relation = "test"; attributes = attrs } in
      match Manipulation.Memory.create_tuple storage db relation tuple with
      | Error _ -> assert false
      | Ok (db, relation, _) ->
        (* Try to insert the same tuple again *)
        match Manipulation.Memory.create_tuple storage db relation tuple with
        | Error (Manipulation.DuplicateTuple _) -> ()
        | _ -> assert false)

let%test_unit "manipulation: tuple_exists check" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty in
    match Manipulation.Memory.create_relation storage db ~name:"test" ~schema with
    | Error _ -> assert false
    | Ok (db, relation) ->
      let attrs = Tuple.AttributeMap.empty
        |> Tuple.AttributeMap.add "v" { Attribute.value = Obj.magic 99 } in
      let tuple : Tuple.materialized = { relation = "test"; attributes = attrs } in
      let tuple_hash = Manipulation.hash_tuple tuple in
      assert (not (Manipulation.Memory.tuple_exists relation tuple_hash));
      match Manipulation.Memory.create_tuple storage db relation tuple with
      | Error _ -> assert false
      | Ok (_db, relation, hash) ->
        assert (hash = tuple_hash);
        assert (Manipulation.Memory.tuple_exists relation tuple_hash))

let%test_unit "manipulation: hash_tuple deterministic" =
  let attrs = Tuple.AttributeMap.empty
    |> Tuple.AttributeMap.add "a" { Attribute.value = Obj.magic 1 }
    |> Tuple.AttributeMap.add "b" { Attribute.value = Obj.magic 2 } in
  let tuple : Tuple.materialized = { relation = "test"; attributes = attrs } in
  let hash1 = Manipulation.hash_tuple tuple in
  let hash2 = Manipulation.hash_tuple tuple in
  assert (hash1 = hash2)

let%test_unit "manipulation: different tuples different hashes" =
  let tuple1 : Tuple.materialized = {
    relation = "test";
    attributes = Tuple.AttributeMap.singleton "x" { Attribute.value = Obj.magic 1 }
  } in
  let tuple2 : Tuple.materialized = {
    relation = "test";
    attributes = Tuple.AttributeMap.singleton "x" { Attribute.value = Obj.magic 2 }
  } in
  let hash1 = Manipulation.hash_tuple tuple1 in
  let hash2 = Manipulation.hash_tuple tuple2 in
  assert (hash1 <> hash2)

let%test_unit "manipulation: get_relation from database" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty
      |> Schema.add "id" "integer" in
    match Manipulation.Memory.create_relation storage db ~name:"items" ~schema with
    | Error _ -> assert false
    | Ok (db, _relation) ->
      (* Now get the relation from the database *)
      match Manipulation.Memory.get_relation db ~name:"items" with
      | None -> assert false
      | Some rel ->
        assert (rel.name = "items");
        assert (rel.schema = schema))

(* ============================================================================
   Schema Persistence Tests
   ============================================================================ *)

let%test_unit "schema: persisted and loaded correctly" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty
      |> Schema.add "id" "integer"
      |> Schema.add "name" "string"
      |> Schema.add "email" "string" in
    match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
    | Error _ -> assert false
    | Ok (db, _relation) ->
      (* Get the relation hash *)
      let rel_hash = Option.get (Management.Database.get_relation_hash db "users") in
      (* Load the relation from storage *)
      match Manipulation.Memory.load_relation storage rel_hash with
      | Error _ -> assert false
      | Ok None -> assert false
      | Ok (Some loaded_rel) ->
        (* Verify schema was persisted and loaded correctly *)
        assert (loaded_rel.schema = schema);
        assert (List.mem ("id", "integer") loaded_rel.schema);
        assert (List.mem ("name", "string") loaded_rel.schema);
        assert (List.mem ("email", "string") loaded_rel.schema))

(* ============================================================================
   System Catalog Tests
   ============================================================================ *)

let%test_unit "catalog: create_database seeds 6 catalog relations" =
  with_storage (fun storage ->
    match Manipulation.Memory.create_database storage ~name:"test" with
    | Error _ -> assert false
    | Ok db ->
      let catalog_names = Prelude.Catalog.catalog_relation_names in
      List.iter (fun name ->
        assert (Management.Database.has_relation db name)
      ) catalog_names)

let%test_unit "catalog: sakura:relation contains all 6 catalog names" =
  with_storage (fun storage ->
    match Manipulation.Memory.create_database storage ~name:"test" with
    | Error _ -> assert false
    | Ok db ->
      let rel = match Manipulation.Memory.get_relation db ~name:"sakura:relation" with
        | None -> assert false
        | Some r -> r
      in
      assert (Manipulation.Memory.tuple_count rel = 6))

let%test_unit "catalog: sakura:on contains insert, update, delete" =
  with_storage (fun storage ->
    match Manipulation.Memory.create_database storage ~name:"test" with
    | Error _ -> assert false
    | Ok db ->
      let on_rel = match Manipulation.Memory.get_relation db ~name:"sakura:on" with
        | None -> assert false
        | Some r -> r
      in
      assert (Manipulation.Memory.tuple_count on_rel = 3))

let%test_unit "catalog: sakura:timing contains immediate, deferred" =
  with_storage (fun storage ->
    match Manipulation.Memory.create_database storage ~name:"test" with
    | Error _ -> assert false
    | Ok db ->
      let timing_rel = match Manipulation.Memory.get_relation db ~name:"sakura:timing" with
        | None -> assert false
        | Some r -> r
      in
      assert (Manipulation.Memory.tuple_count timing_rel = 2))

let%test_unit "catalog: sakura:domain seeded with 4 prelude domains" =
  with_storage (fun storage ->
    match Manipulation.Memory.create_database storage ~name:"test" with
    | Error _ -> assert false
    | Ok db ->
      let dom_rel = match Manipulation.Memory.get_relation db ~name:"sakura:domain" with
        | None -> assert false
        | Some r -> r
      in
      assert (Manipulation.Memory.tuple_count dom_rel = 4))

let%test_unit "catalog: create_relation updates sakura:relation" =
  with_storage (fun storage ->
    match Manipulation.Memory.create_database storage ~name:"test" with
    | Error _ -> assert false
    | Ok db ->
      let schema = Schema.empty |> Schema.add "id" "natural" in
      let db = match Manipulation.Memory.create_relation storage db ~name:"employees" ~schema with
        | Error _ -> assert false | Ok (db, _) -> db
      in
      let rel = match Manipulation.Memory.get_relation db ~name:"sakura:relation" with
        | None -> assert false | Some r -> r
      in
      (* 6 catalog relations + 1 user relation *)
      assert (Manipulation.Memory.tuple_count rel = 7))

let%test_unit "catalog: create_relation updates sakura:attribute" =
  with_storage (fun storage ->
    match Manipulation.Memory.create_database storage ~name:"test" with
    | Error _ -> assert false
    | Ok db ->
      let schema = Schema.empty |> Schema.add "id" "natural" in
      let db = match Manipulation.Memory.create_relation storage db ~name:"employees" ~schema with
        | Error _ -> assert false | Ok (db, _) -> db
      in
      let attr_rel = match Manipulation.Memory.get_relation db ~name:"sakura:attribute" with
        | None -> assert false | Some r -> r
      in
      (* catalog attribute tuples (sum of schema sizes of all 6 catalog relations) + 1 for employees *)
      (* sakura:relation: 1, sakura:domain: 1, sakura:attribute: 3, sakura:constraint: 2,
         sakura:on: 1, sakura:timing: 1  => 9 catalog attrs + 1 for employees = 10 *)
      let count = Manipulation.Memory.tuple_count attr_rel in
      assert (count = 10))

let%test_unit "catalog: retract_relation removes from sakura:relation" =
  with_storage (fun storage ->
    match Manipulation.Memory.create_database storage ~name:"test" with
    | Error _ -> assert false
    | Ok db ->
      let schema = Schema.empty |> Schema.add "id" "natural" in
      let db = match Manipulation.Memory.create_relation storage db ~name:"employees" ~schema with
        | Error _ -> assert false | Ok (db, _) -> db
      in
      let db = match Manipulation.Memory.retract_relation storage db ~name:"employees" with
        | Error _ -> assert false | Ok db -> db
      in
      let rel = match Manipulation.Memory.get_relation db ~name:"sakura:relation" with
        | None -> assert false | Some r -> r
      in
      (* Back to 6 catalog relations *)
      assert (Manipulation.Memory.tuple_count rel = 6))

let%test_unit "catalog: register_constraint inserts into sakura:constraint" =
  with_storage (fun storage ->
    match Manipulation.Memory.create_database storage ~name:"test" with
    | Error _ -> assert false
    | Ok db ->
      let schema = Schema.empty |> Schema.add "id" "natural" in
      let db = match Manipulation.Memory.create_relation storage db ~name:"orders" ~schema with
        | Error _ -> assert false | Ok (db, _) -> db
      in
      let db = match Manipulation.Memory.register_constraint storage db
          ~constraint_name:"orders_id_positive"
          ~relation_name:"orders"
          ~body:(Constraint.And []) with
        | Error _ -> assert false | Ok db -> db
      in
      let con_rel = match Manipulation.Memory.get_relation db ~name:"sakura:constraint" with
        | None -> assert false | Some r -> r
      in
      assert (Manipulation.Memory.tuple_count con_rel = 1))

(* ============================================================================
   Integration Tests
   ============================================================================ *)

let%test_unit "integration: full workflow with storage" =
  with_storage (fun storage ->
    (* Create database *)
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in

    (* Create products relation *)
    let schema = Schema.empty
      |> Schema.add "id" "integer"
      |> Schema.add "name" "string"
      |> Schema.add "price" "integer" in

    let (db, products) = match Manipulation.Memory.create_relation storage db ~name:"products" ~schema with
      | Error _ -> assert false
      | Ok x -> x
    in

    (* Insert some products *)
    let make_product id name price =
      let attrs = Tuple.AttributeMap.empty
        |> Tuple.AttributeMap.add "id" { Attribute.value = Obj.magic id }
        |> Tuple.AttributeMap.add "name" { Attribute.value = Obj.magic name }
        |> Tuple.AttributeMap.add "price" { Attribute.value = Obj.magic price } in
      ({ Tuple.relation = "products"; attributes = attrs } : Tuple.materialized)
    in

    let tuples = [
      make_product 1 "Apple" 100;
      make_product 2 "Banana" 50;
      make_product 3 "Cherry" 200;
    ] in

    let (db, products, hashes) = match Manipulation.Memory.create_tuples storage db products tuples with
      | Error _ -> assert false
      | Ok x -> x
    in

    assert (Manipulation.Memory.tuple_count products = 3);
    assert (List.length hashes = 3);

    (* Verify we can load all tuples back *)
    (match Manipulation.Memory.load_tuples storage hashes with
     | Error _ -> assert false
     | Ok loaded -> assert (List.length loaded = 3));

    (* Delete one product *)
    let banana_hash = Manipulation.hash_tuple (make_product 2 "Banana" 50) in
    let (_db, products) = match Manipulation.Memory.retract_tuple storage db products ~tuple_hash:banana_hash with
      | Error _ -> assert false
      | Ok x -> x
    in

    assert (Manipulation.Memory.tuple_count products = 2);

    (* Verify remaining hashes *)
    let remaining_hashes = Manipulation.Memory.tuple_hashes products in
    assert (List.length remaining_hashes = 2);
    assert (not (List.mem banana_hash remaining_hashes));

    (* But banana data is still in storage (append-only) *)
    match Manipulation.Memory.load_tuple storage banana_hash with
    | Error _ -> assert false
    | Ok None -> assert false
    | Ok (Some loaded) ->
      let name_attr = Tuple.AttributeMap.find "name" loaded.attributes in
      assert ((Obj.magic name_attr.Attribute.value : string) = "Banana"))

let%test_unit "integration: database history tracking" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"versioned" with
      | Error _ -> assert false | Ok db -> db
    in
    let initial_hash = db.hash in

    let schema = Schema.empty in
    let (db, _) = match Manipulation.Memory.create_relation storage db ~name:"rel1" ~schema with
      | Error _ -> assert false
      | Ok x -> x
    in

    (* After first change, initial hash should be in history *)
    assert (db.hash <> initial_hash);

    let hash_after_rel1 = db.hash in

    let (db, _) = match Manipulation.Memory.create_relation storage db ~name:"rel2" ~schema with
      | Error _ -> assert false
      | Ok x -> x
    in

    (* After second change, previous hash should be in history *)
    assert (db.hash <> hash_after_rel1);
    assert (List.mem hash_after_rel1 db.history))

let%test_unit "integration: hash bubbles up correctly" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty in

    let (db, relation) = match Manipulation.Memory.create_relation storage db ~name:"items" ~schema with
      | Error _ -> assert false
      | Ok x -> x
    in

    let db_hash_before = db.hash in
    let rel_hash_before = relation.hash in

    (* Insert a tuple *)
    let attrs = Tuple.AttributeMap.empty
      |> Tuple.AttributeMap.add "x" { Attribute.value = Obj.magic 1 } in
    let tuple : Tuple.materialized = { relation = "items"; attributes = attrs } in

    let (db, relation, _) = match Manipulation.Memory.create_tuple storage db relation tuple with
      | Error _ -> assert false
      | Ok x -> x
    in

    (* Relation hash should change *)
    assert (relation.hash <> rel_hash_before);

    (* Database hash should change *)
    assert (db.hash <> db_hash_before);

    (* Old database hash should be in history *)
    assert (List.mem db_hash_before db.history);

    (* Database's merkle tree should contain the new relation hash *)
    match relation.hash with
    | None -> assert false
    | Some rel_hash ->
      assert (Merkle.member rel_hash db.tree))

(* ============================================================================
   Time-Travel / Branching Tests
   ============================================================================ *)

let%test_unit "branching: load database from historical hash" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty in

    (* Create relation and add a tuple *)
    let (db, relation) = match Manipulation.Memory.create_relation storage db ~name:"items" ~schema with
      | Error _ -> assert false
      | Ok x -> x
    in

    let attrs = Tuple.AttributeMap.empty
      |> Tuple.AttributeMap.add "x" { Attribute.value = Obj.magic 1 } in
    let tuple : Tuple.materialized = { relation = "items"; attributes = attrs } in

    let (db, _relation, _) = match Manipulation.Memory.create_tuple storage db relation tuple with
      | Error _ -> assert false
      | Ok x -> x
    in

    (* Capture hash H1 - database with 1 tuple *)
    let h1 = db.hash in

    (* Add another tuple *)
    let attrs2 = Tuple.AttributeMap.empty
      |> Tuple.AttributeMap.add "x" { Attribute.value = Obj.magic 2 } in
    let tuple2 : Tuple.materialized = { relation = "items"; attributes = attrs2 } in

    (* Get relation from database - it's now integrated! *)
    let relation = match Manipulation.Memory.get_relation db ~name:"items" with
      | None -> assert false
      | Some r -> r
    in

    let (db, _relation, _) = match Manipulation.Memory.create_tuple storage db relation tuple2 with
      | Error _ -> assert false
      | Ok x -> x
    in

    let h2 = db.hash in
    assert (h1 <> h2);

    (* Now load H1 from storage - should get database state with 1 tuple *)
    match Manipulation.Memory.load_database storage h1 with
    | Error _ -> assert false
    | Ok None -> assert false
    | Ok (Some loaded_db) ->
      assert (loaded_db.hash = h1);
      assert (loaded_db.name = "test");
      (* The relation is now loaded directly in the database *)
      match Manipulation.Memory.get_relation loaded_db ~name:"items" with
      | None -> assert false
      | Some loaded_rel ->
        (* Should have 1 tuple *)
        assert (Manipulation.Memory.tuple_count loaded_rel = 1))

let%test_unit "branching: branch from historical state" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty in

    (* Create relation *)
    let (db, relation) = match Manipulation.Memory.create_relation storage db ~name:"data" ~schema with
      | Error _ -> assert false
      | Ok x -> x
    in

    (* Add tuple A *)
    let tuple_a : Tuple.materialized = {
      relation = "data";
      attributes = Tuple.AttributeMap.singleton "v" { Attribute.value = Obj.magic "A" }
    } in
    let (db, relation, _) = match Manipulation.Memory.create_tuple storage db relation tuple_a with
      | Error _ -> assert false
      | Ok x -> x
    in

    (* Capture H1 - state with tuple A *)
    let h1 = db.hash in

    (* Continue on main branch: add tuple B *)
    let tuple_b : Tuple.materialized = {
      relation = "data";
      attributes = Tuple.AttributeMap.singleton "v" { Attribute.value = Obj.magic "B" }
    } in
    let (db_main, relation_main, _) = match Manipulation.Memory.create_tuple storage db relation tuple_b with
      | Error _ -> assert false
      | Ok x -> x
    in
    let h2 = db_main.hash in

    (* Now branch from H1 and add tuple C instead *)
    let db_branch = match Manipulation.Memory.load_database storage h1 with
      | Error _ -> assert false
      | Ok None -> assert false
      | Ok (Some d) -> d
    in
    (* Relation is now loaded directly in the database *)
    let relation_branch = match Manipulation.Memory.get_relation db_branch ~name:"data" with
      | None -> assert false
      | Some r -> r
    in

    let tuple_c : Tuple.materialized = {
      relation = "data";
      attributes = Tuple.AttributeMap.singleton "v" { Attribute.value = Obj.magic "C" }
    } in
    let (db_branch, _relation_branch, _) = match Manipulation.Memory.create_tuple storage db_branch relation_branch tuple_c with
      | Error _ -> assert false
      | Ok x -> x
    in
    let h3 = db_branch.hash in

    (* Verify: H1, H2, H3 are all different *)
    assert (h1 <> h2);
    assert (h1 <> h3);
    assert (h2 <> h3);

    (* H2 (main branch) has tuples A and B *)
    assert (Manipulation.Memory.tuple_count relation_main = 2);

    (* H1 is still loadable and unchanged *)
    match Manipulation.Memory.load_database storage h1 with
    | Error _ -> assert false
    | Ok None -> assert false
    | Ok (Some loaded_h1) ->
      match Manipulation.Memory.get_relation loaded_h1 ~name:"data" with
      | None -> assert false
      | Some r ->
        assert (Manipulation.Memory.tuple_count r = 1))

let%test_unit "branching: full reconstruction from hash" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty in

    (* Create relation *)
    let (db, relation) = match Manipulation.Memory.create_relation storage db ~name:"products" ~schema with
      | Error _ -> assert false
      | Ok x -> x
    in

    (* Add products *)
    let make_product name =
      { Tuple.relation = "products";
        attributes = Tuple.AttributeMap.singleton "name" { Attribute.value = Obj.magic name } }
    in
    let (db, _relation, _) = match Manipulation.Memory.create_tuples storage db relation
        [make_product "Apple"; make_product "Banana"; make_product "Cherry"] with
      | Error _ -> assert false
      | Ok x -> x
    in

    let saved_hash = db.hash in

    (* Now reconstruct everything from just the hash *)
    match Manipulation.Memory.load_database storage saved_hash with
    | Error _ -> assert false
    | Ok None -> assert false
    | Ok (Some loaded_db) ->
      (* Relation is now loaded directly in the database *)
      match Manipulation.Memory.get_relation loaded_db ~name:"products" with
      | None -> assert false
      | Some loaded_rel ->
        (* Get tuple hashes from relation *)
        let tuple_hashes = Manipulation.Memory.tuple_hashes loaded_rel in
        assert (List.length tuple_hashes = 3);

        (* Load all tuples *)
        match Manipulation.Memory.load_tuples storage tuple_hashes with
        | Error _ -> assert false
        | Ok tuples ->
          assert (List.length tuples = 3);
          let names = List.map (fun t ->
            let attr = Tuple.AttributeMap.find "name" t.Tuple.attributes in
            (Obj.magic attr.Attribute.value : string)
          ) tuples in
          assert (List.mem "Apple" names);
          assert (List.mem "Banana" names);
          assert (List.mem "Cherry" names))

(* ============================================================================
   Algebra Tests
   ============================================================================ *)

(* Helper: build a materialized tuple with int attributes *)
let make_int_tuple relation pairs =
  let attributes =
    List.fold_left (fun acc (k, v) ->
      Tuple.AttributeMap.add k { Attribute.value = Obj.repr (v : int) } acc)
      Tuple.AttributeMap.empty pairs
  in
  (Tuple.Materialized { Tuple.relation; attributes } : Tuple.t)

(* Helper: build a stored relation with one integer column and given values *)
let stored_relation_with_ints storage db ~name ~attr values =
  let schema = Schema.empty |> Schema.add attr "integer" in
  let (db, rel) = match Manipulation.Memory.create_relation storage db ~name ~schema with
    | Error _ -> assert false | Ok x -> x
  in
  let tuples = List.map (fun v ->
    let attributes =
      Tuple.AttributeMap.singleton attr { Attribute.value = Obj.repr (v : int) }
    in
    ({ Tuple.relation = name; attributes } : Tuple.materialized)
  ) values in
  let (db, rel, _) = match Manipulation.Memory.create_tuples storage db rel tuples with
    | Error _ -> assert false | Ok x -> x
  in
  (db, rel)

let%test_unit "algebra: const_relation single tuple" =
  with_storage (fun storage ->
    let rel = Algebra.Memory.const_relation
        [ "x", Obj.repr (42 : int);
          "y", Obj.repr (99 : int) ] in
    match Algebra.Memory.materialize storage rel with
    | Error _    -> assert false
    | Ok [tup]   ->
      let x: int = Obj.obj (Tuple.AttributeMap.find "x" tup.Tuple.attributes).Attribute.value in
      assert (x = 42)
    | Ok _       -> assert false)

let%test_unit "algebra: select_fn with predicate" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let (_, rel) = stored_relation_with_ints storage db ~name:"nums" ~attr:"n" [1;2;3;4;5] in
    let predicate = function
      | Tuple.Materialized t ->
        let v: int = Obj.obj (Tuple.AttributeMap.find "n" t.Tuple.attributes).Attribute.value in
        v > 3
      | _ -> false
    in
    match Algebra.Memory.select_fn storage predicate rel with
    | Error _   -> assert false
    | Ok result ->
      match Algebra.Memory.materialize storage result with
      | Error _ -> assert false
      | Ok rows ->
        assert (List.length rows = 2);
        List.iter (fun t ->
          let v: int = Obj.obj (Tuple.AttributeMap.find "n" t.Tuple.attributes).Attribute.value in
          assert (v > 3)) rows)

let%test_unit "algebra: project restricts schema" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty |> Schema.add "a" "integer" |> Schema.add "b" "integer" in
    let (db, rel) = match Manipulation.Memory.create_relation storage db ~name:"ab" ~schema with
      | Error _ -> assert false | Ok x -> x
    in
    let attrs = Tuple.AttributeMap.empty
      |> Tuple.AttributeMap.add "a" { Attribute.value = Obj.repr (1 : int) }
      |> Tuple.AttributeMap.add "b" { Attribute.value = Obj.repr (2 : int) } in
    let (_, rel, _) = match Manipulation.Memory.create_tuple storage db rel
        { Tuple.relation = "ab"; attributes = attrs } with
      | Error _ -> assert false | Ok x -> x
    in
    match Algebra.Memory.project storage ["a"] rel with
    | Error _ -> assert false
    | Ok projected ->
      match Algebra.Memory.materialize storage projected with
      | Error _ -> assert false
      | Ok [t] ->
        assert (Tuple.AttributeMap.mem "a" t.Tuple.attributes);
        assert (not (Tuple.AttributeMap.mem "b" t.Tuple.attributes))
      | Ok _ -> assert false)

let%test_unit "algebra: rename changes attr names" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let (_, rel) = stored_relation_with_ints storage db ~name:"r" ~attr:"x" [7] in
    match Algebra.Memory.rename storage [("x", "y")] rel with
    | Error _ -> assert false
    | Ok renamed ->
      match Algebra.Memory.materialize storage renamed with
      | Error _ -> assert false
      | Ok [t] ->
        assert (not (Tuple.AttributeMap.mem "x" t.Tuple.attributes));
        assert (Tuple.AttributeMap.mem "y" t.Tuple.attributes);
        let v: int = Obj.obj (Tuple.AttributeMap.find "y" t.Tuple.attributes).Attribute.value in
        assert (v = 7)
      | Ok _ -> assert false)

let%test_unit "algebra: equijoin merges matching tuples" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    (* left: {id=1, name="Alice"}, {id=2, name="Bob"} *)
    let schema_l = Schema.empty |> Schema.add "id" "integer" |> Schema.add "name" "string" in
    let (db, left) = match Manipulation.Memory.create_relation storage db ~name:"L" ~schema:schema_l with
      | Error _ -> assert false | Ok x -> x
    in
    let make_left id name =
      let attrs = Tuple.AttributeMap.empty
        |> Tuple.AttributeMap.add "id"   { Attribute.value = Obj.repr (id : int) }
        |> Tuple.AttributeMap.add "name" { Attribute.value = Obj.repr (name : string) } in
      ({ Tuple.relation = "L"; attributes = attrs } : Tuple.materialized)
    in
    let (db, left, _) = match Manipulation.Memory.create_tuples storage db left
        [make_left 1 "Alice"; make_left 2 "Bob"] with
      | Error _ -> assert false | Ok x -> x
    in
    (* right: {id=1, score=100}, {id=3, score=999} *)
    let schema_r = Schema.empty |> Schema.add "id" "integer" |> Schema.add "score" "integer" in
    let (db, right) = match Manipulation.Memory.create_relation storage db ~name:"R" ~schema:schema_r with
      | Error _ -> assert false | Ok x -> x
    in
    let make_right id score =
      let attrs = Tuple.AttributeMap.empty
        |> Tuple.AttributeMap.add "id"    { Attribute.value = Obj.repr (id : int) }
        |> Tuple.AttributeMap.add "score" { Attribute.value = Obj.repr (score : int) } in
      ({ Tuple.relation = "R"; attributes = attrs } : Tuple.materialized)
    in
    let (_, right, _) = match Manipulation.Memory.create_tuples storage db right
        [make_right 1 100; make_right 3 999] with
      | Error _ -> assert false | Ok x -> x
    in
    match Algebra.Memory.equijoin storage ["id"] left right with
    | Error _  -> assert false
    | Ok joined ->
      match Algebra.Memory.materialize storage joined with
      | Error _ -> assert false
      | Ok rows ->
        (* Only id=1 matches *)
        assert (List.length rows = 1);
        let t = List.hd rows in
        let score: int = Obj.obj (Tuple.AttributeMap.find "score" t.Tuple.attributes).Attribute.value in
        assert (score = 100))

let%test_unit "algebra: equijoin empty match" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let (db, left) = stored_relation_with_ints storage db ~name:"L" ~attr:"id" [1;2] in
    let (_, right) = stored_relation_with_ints storage db ~name:"R" ~attr:"id" [9;8] in
    match Algebra.Memory.equijoin storage ["id"] left right with
    | Error _  -> assert false
    | Ok joined ->
      match Algebra.Memory.materialize storage joined with
      | Error _ -> assert false
      | Ok rows -> assert (List.length rows = 0))

let%test_unit "algebra: union concatenates streams" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let (db, r1) = stored_relation_with_ints storage db ~name:"A" ~attr:"n" [1;2] in
    let (_, r2) = stored_relation_with_ints storage db ~name:"B" ~attr:"n" [3;4] in
    match Algebra.Memory.union storage r1 r2 with
    | Error _    -> assert false
    | Ok unioned ->
      match Algebra.Memory.materialize storage unioned with
      | Error _ -> assert false
      | Ok rows ->
        assert (List.length rows = 4);
        let vals = List.map (fun t ->
          Obj.obj (Tuple.AttributeMap.find "n" t.Tuple.attributes).Attribute.value
        ) rows in
        assert (List.mem 1 vals);
        assert (List.mem 2 vals);
        assert (List.mem 3 vals);
        assert (List.mem 4 vals))

let%test_unit "algebra: diff removes right from left" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let (db, r1) = stored_relation_with_ints storage db ~name:"A" ~attr:"n" [1;2;3] in
    let (_, r2) = stored_relation_with_ints storage db ~name:"B" ~attr:"n" [2;3] in
    match Algebra.Memory.diff storage r1 r2 with
    | Error _   -> assert false
    | Ok result ->
      match Algebra.Memory.materialize storage result with
      | Error _ -> assert false
      | Ok rows ->
        assert (List.length rows = 1);
        let v: int = Obj.obj (Tuple.AttributeMap.find "n" (List.hd rows).Tuple.attributes).Attribute.value in
        assert (v = 1))

let%test_unit "algebra: take limits output" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let (_, rel) = stored_relation_with_ints storage db ~name:"big" ~attr:"n" [10;20;30;40;50] in
    match Algebra.Memory.take storage 3 rel with
    | Error _   -> assert false
    | Ok result ->
      match Algebra.Memory.materialize storage result with
      | Error _ -> assert false
      | Ok rows -> assert (List.length rows = 3))

(* ============================================================================
   DRL Parser Tests
   ============================================================================ *)

let%test_unit "drl: parse Base" =
  match Drl.Parser.of_string {|(Base "users")|} with
  | Error _              -> assert false
  | Ok (Drl.Ast.Base s)  -> assert (s = "users")
  | Ok _                 -> assert false

let%test_unit "drl: parse Const" =
  match Drl.Parser.of_string {|(Const (("age" (Int 18))))|} with
  | Error _                    -> assert false
  | Ok (Drl.Ast.Const [("age", Drl.Ast.Int 18)]) -> ()
  | Ok _                       -> assert false

let%test_unit "drl: parse Join" =
  match Drl.Parser.of_string {|(Join (id) (Base "L") (Base "R"))|} with
  | Error _                             -> assert false
  | Ok (Drl.Ast.Join (["id"], Drl.Ast.Base "L", Drl.Ast.Base "R")) -> ()
  | Ok _                                -> assert false

let%test_unit "drl: parse Select" =
  let s = {|(Select (Const (("age" (Int 18)))) (Base "users"))|} in
  match Drl.Parser.of_string s with
  | Error _ -> assert false
  | Ok (Drl.Ast.Select (Drl.Ast.Const _, Drl.Ast.Base "users")) -> ()
  | Ok _    -> assert false

(* ============================================================================
   DRL Executor end-to-end Tests
   ============================================================================ *)

let%test_unit "drl: execute Base" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    let (db, _) = stored_relation_with_ints storage db ~name:"items" ~attr:"v" [10; 20] in
    match Drl.Parser.of_string {|(Base "items")|} with
    | Error _   -> assert false
    | Ok query  ->
      match Drl.Executor.Memory.execute storage db query with
      | Error _   -> assert false
      | Ok rel    ->
        match Algebra.Memory.materialize storage rel with
        | Error _ -> assert false
        | Ok rows -> assert (List.length rows = 2))

let%test_unit "drl: execute Select+Const" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"test_db" with
      | Error _ -> assert false | Ok db -> db
    in
    (* users: {age=18, name="Alice"}, {age=25, name="Bob"} *)
    let schema = Schema.empty |> Schema.add "age" "integer" |> Schema.add "name" "string" in
    let (db, users) = match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
      | Error _ -> assert false | Ok x -> x
    in
    let make_user age name =
      let attrs = Tuple.AttributeMap.empty
        |> Tuple.AttributeMap.add "age"  { Attribute.value = Obj.repr (age : int) }
        |> Tuple.AttributeMap.add "name" { Attribute.value = Obj.repr (name : string) } in
      ({ Tuple.relation = "users"; attributes = attrs } : Tuple.materialized)
    in
    let (db, _, _) = match Manipulation.Memory.create_tuples storage db users
        [make_user 18 "Alice"; make_user 25 "Bob"] with
      | Error _ -> assert false | Ok x -> x
    in
    (* Query: select users where age = 18 *)
    let s = {|(Select (Const (("age" (Int 18)))) (Base "users"))|} in
    match Drl.Parser.of_string s with
    | Error _  -> assert false
    | Ok query ->
      match Drl.Executor.Memory.execute storage db query with
      | Error _  -> assert false
      | Ok rel   ->
        match Algebra.Memory.materialize storage rel with
        | Error _ -> assert false
        | Ok rows ->
          assert (List.length rows = 1);
          let name_v: string =
            Obj.obj (Tuple.AttributeMap.find "name" (List.hd rows).Tuple.attributes).Attribute.value
          in
          assert (name_v = "Alice"))

(* ============================================================================
   Constraint System Tests
   ============================================================================ *)

(* ---------- Constraint construction ---------- *)

let%test_unit "constraint: vars_in MemberOf" =
  let b =
    Constraint.BindingMap.empty
    |> Constraint.BindingMap.add "left" (Constraint.Var "x")
    |> Constraint.BindingMap.add "right" (Constraint.Const (Obj.repr 10))
  in
  let c = Constraint.MemberOf { target = "less_than"; binding = b } in
  let vars = Constraint.vars_in c in
  assert (List.mem "x" vars);
  assert (not (List.mem "right" vars))

let%test_unit "constraint: vars_in And" =
  let b1 =
    Constraint.BindingMap.singleton "left" (Constraint.Var "a")
  in
  let b2 =
    Constraint.BindingMap.singleton "left" (Constraint.Var "b")
  in
  let c =
    Constraint.And
      [
        Constraint.MemberOf { target = "t1"; binding = b1 };
        Constraint.MemberOf { target = "t2"; binding = b2 };
      ]
  in
  let vars = Constraint.vars_in c in
  assert (List.mem "a" vars);
  assert (List.mem "b" vars)

let%test_unit "constraint: rename_vars" =
  let b =
    Constraint.BindingMap.singleton "left" (Constraint.Var "old_name")
  in
  let c = Constraint.MemberOf { target = "t"; binding = b } in
  let c' = Constraint.rename_vars [ ("old_name", "new_name") ] c in
  let vars = Constraint.vars_in c' in
  assert (List.mem "new_name" vars);
  assert (not (List.mem "old_name" vars))

let%test_unit "constraint: filter_by_attrs keeps relevant" =
  let b =
    Constraint.BindingMap.singleton "left" (Constraint.Var "x")
  in
  let c = Constraint.MemberOf { target = "t"; binding = b } in
  assert (Constraint.filter_by_attrs [ "x" ] c <> None);
  assert (Constraint.filter_by_attrs [ "y" ] c = None)

let%test_unit "constraint: merge named constraints" =
  let b = Constraint.BindingMap.empty in
  let cs1 = [ ("c1", Constraint.MemberOf { target = "t1"; binding = b }) ] in
  let cs2 = [ ("c2", Constraint.MemberOf { target = "t2"; binding = b }) ] in
  let merged = Constraint.merge cs1 cs2 in
  assert (List.length merged = 2)

let%test_unit "constraint: merge duplicate names produces And" =
  let b = Constraint.BindingMap.empty in
  let c1 = Constraint.MemberOf { target = "t1"; binding = b } in
  let c2 = Constraint.MemberOf { target = "t2"; binding = b } in
  let merged = Constraint.merge [ ("shared", c1) ] [ ("shared", c2) ] in
  assert (List.length merged = 1);
  match List.assoc "shared" merged with
  | Constraint.And _ -> ()
  | _ -> assert false

(* ---------- Smart constructors ---------- *)

let%test_unit "constraint: and_ singleton" =
  let b = Constraint.BindingMap.empty in
  let c = Constraint.MemberOf { target = "t"; binding = b } in
  match Constraint.and_ [ c ] with
  | Constraint.MemberOf _ -> ()
  | _ -> assert false

let%test_unit "constraint: or_ singleton" =
  let b = Constraint.BindingMap.empty in
  let c = Constraint.MemberOf { target = "t"; binding = b } in
  match Constraint.or_ [ c ] with
  | Constraint.MemberOf _ -> ()
  | _ -> assert false

(* ---------- Comparison shorthands ---------- *)

let%test_unit "constraint: lt shorthand" =
  match Constraint.lt ~left:(Var "x") ~right:(Const (Obj.repr 5)) with
  | Constraint.MemberOf { target = "less_than"; _ } -> ()
  | _ -> assert false

let%test_unit "constraint: between shorthand" =
  match
    Constraint.between ~value:(Var "x") ~low:(Const (Obj.repr 0))
      ~high:(Const (Obj.repr 100))
  with
  | Constraint.And [ _; _ ] -> ()
  | _ -> assert false

(* ---------- Binding resolution ---------- *)

let%test_unit "constraint: bind resolves Var and Const" =
  let b =
    Constraint.BindingMap.empty
    |> Constraint.BindingMap.add "left" (Constraint.Var "x")
    |> Constraint.BindingMap.add "right" (Constraint.Const (Obj.repr 42))
  in
  let tuple : Tuple.materialized =
    {
      relation = "test";
      attributes =
        Tuple.AttributeMap.singleton "x" { Attribute.value = Obj.repr 10 };
    }
  in
  let bound = Constraint.bind b tuple in
  assert (List.length bound = 2);
  let left_v : int = Obj.obj (List.assoc "left" bound) in
  let right_v : int = Obj.obj (List.assoc "right" bound) in
  assert (left_v = 10);
  assert (right_v = 42)

(* ---------- Evaluation engine ---------- *)

let make_eval_ctx ?(relations = []) () : Constraint.eval_context =
  {
    check_membership =
      (fun rel_name bound_pairs ->
        match List.assoc_opt rel_name relations with
        | None -> false
        | Some checker -> checker bound_pairs);
    iterate_finite =
      (fun rel_name ->
        match List.assoc_opt rel_name relations with
        | None -> None
        | Some _ -> Some []);
  }

let%test_unit "constraint: evaluate MemberOf success" =
  let ctx =
    make_eval_ctx
      ~relations:[ ("my_rel", fun _pairs -> true) ]
      ()
  in
  let b = Constraint.BindingMap.empty in
  let c = Constraint.MemberOf { target = "my_rel"; binding = b } in
  let tuple : Tuple.materialized =
    { relation = "test"; attributes = Tuple.AttributeMap.empty }
  in
  match Constraint.evaluate ctx tuple c with
  | Ok true -> ()
  | _ -> assert false

let%test_unit "constraint: evaluate MemberOf failure" =
  let ctx =
    make_eval_ctx
      ~relations:[ ("my_rel", fun _pairs -> false) ]
      ()
  in
  let b = Constraint.BindingMap.empty in
  let c = Constraint.MemberOf { target = "my_rel"; binding = b } in
  let tuple : Tuple.materialized =
    { relation = "test"; attributes = Tuple.AttributeMap.empty }
  in
  match Constraint.evaluate ctx tuple c with
  | Error (Constraint.MembershipFailed _) -> ()
  | _ -> assert false

let%test_unit "constraint: evaluate And short-circuits" =
  let call_count = ref 0 in
  let ctx =
    make_eval_ctx
      ~relations:
        [
          ( "fail_rel",
            fun _ ->
              incr call_count;
              false );
          ( "ok_rel",
            fun _ ->
              incr call_count;
              true );
        ]
      ()
  in
  let b = Constraint.BindingMap.empty in
  let c =
    Constraint.And
      [
        Constraint.MemberOf { target = "fail_rel"; binding = b };
        Constraint.MemberOf { target = "ok_rel"; binding = b };
      ]
  in
  let tuple : Tuple.materialized =
    { relation = "test"; attributes = Tuple.AttributeMap.empty }
  in
  (match Constraint.evaluate ctx tuple c with
   | Error _ -> ()
   | _ -> assert false);
  (* Second branch should not have been called *)
  assert (!call_count = 1)

let%test_unit "constraint: evaluate Or succeeds on first match" =
  let ctx =
    make_eval_ctx
      ~relations:
        [
          ("a", fun _ -> false);
          ("b", fun _ -> true);
        ]
      ()
  in
  let b = Constraint.BindingMap.empty in
  let c =
    Constraint.Or
      [
        Constraint.MemberOf { target = "a"; binding = b };
        Constraint.MemberOf { target = "b"; binding = b };
      ]
  in
  let tuple : Tuple.materialized =
    { relation = "test"; attributes = Tuple.AttributeMap.empty }
  in
  match Constraint.evaluate ctx tuple c with
  | Ok true -> ()
  | _ -> assert false

let%test_unit "constraint: evaluate Not negates" =
  let ctx : Constraint.eval_context =
    {
      check_membership =
        (fun rel_name _pairs ->
          match rel_name with
          | "universe" -> true
          | "body_rel" -> false
          | _ -> false);
      iterate_finite = (fun _ -> None);
    }
  in
  let b = Constraint.BindingMap.empty in
  let c =
    Constraint.Not
      {
        body = Constraint.MemberOf { target = "body_rel"; binding = b };
        universe = "universe";
      }
  in
  let tuple : Tuple.materialized =
    { relation = "test"; attributes = Tuple.AttributeMap.empty }
  in
  match Constraint.evaluate ctx tuple c with
  | Ok true -> ()
  | _ -> assert false

let%test_unit "constraint: evaluate Exists over finite relation" =
  let ctx : Constraint.eval_context =
    {
      check_membership =
        (fun _rel_name pairs ->
          match List.assoc_opt "left" pairs, List.assoc_opt "right" pairs with
          | Some l, Some r -> (Obj.obj l : int) < (Obj.obj r : int)
          | _ -> false);
      iterate_finite =
        (fun rel_name ->
          if rel_name = "small_set" then
            Some
              [
                [ ("value", Obj.repr 1) ];
                [ ("value", Obj.repr 5) ];
                [ ("value", Obj.repr 10) ];
              ]
          else None);
    }
  in
  let b =
    Constraint.BindingMap.empty
    |> Constraint.BindingMap.add "left" (Constraint.Var "x")
    |> Constraint.BindingMap.add "right" (Constraint.Var "value")
  in
  let c =
    Constraint.Exists
      {
        variable = "value";
        quantifier = "small_set";
        body = Constraint.MemberOf { target = "less_than"; binding = b };
      }
  in
  (* x=3, exists value in {1,5,10} where 3 < value => true (5 or 10 work) *)
  let tuple : Tuple.materialized =
    {
      relation = "test";
      attributes =
        Tuple.AttributeMap.singleton "x" { Attribute.value = Obj.repr 3 };
    }
  in
  match Constraint.evaluate ctx tuple c with
  | Ok true -> ()
  | _ -> assert false

let%test_unit "constraint: evaluate Forall fails when not all match" =
  let ctx : Constraint.eval_context =
    {
      check_membership =
        (fun _rel_name pairs ->
          match List.assoc_opt "left" pairs, List.assoc_opt "right" pairs with
          | Some l, Some r -> (Obj.obj l : int) < (Obj.obj r : int)
          | _ -> false);
      iterate_finite =
        (fun rel_name ->
          if rel_name = "small_set" then
            Some
              [
                [ ("value", Obj.repr 1) ];
                [ ("value", Obj.repr 5) ];
              ]
          else None);
    }
  in
  let b =
    Constraint.BindingMap.empty
    |> Constraint.BindingMap.add "left" (Constraint.Var "x")
    |> Constraint.BindingMap.add "right" (Constraint.Var "value")
  in
  let c =
    Constraint.Forall
      {
        variable = "value";
        quantifier = "small_set";
        body = Constraint.MemberOf { target = "less_than"; binding = b };
      }
  in
  (* x=3, forall value in {1,5} where 3 < value => false (3 is not < 1) *)
  let tuple : Tuple.materialized =
    {
      relation = "test";
      attributes =
        Tuple.AttributeMap.singleton "x" { Attribute.value = Obj.repr 3 };
    }
  in
  match Constraint.evaluate ctx tuple c with
  | Ok false -> ()
  | _ -> assert false

let%test_unit "constraint: Forall unbounded quantifier errors" =
  let ctx : Constraint.eval_context =
    {
      check_membership = (fun _ _ -> true);
      iterate_finite = (fun _ -> None);
    }
  in
  let b = Constraint.BindingMap.empty in
  let c =
    Constraint.Forall
      {
        variable = "v";
        quantifier = "infinite_rel";
        body = Constraint.MemberOf { target = "t"; binding = b };
      }
  in
  let tuple : Tuple.materialized =
    { relation = "test"; attributes = Tuple.AttributeMap.empty }
  in
  match Constraint.evaluate ctx tuple c with
  | Error (Constraint.UnboundedQuantifier _) -> ()
  | _ -> assert false

(* ---------- Integrated constraint enforcement in manipulation ---------- *)

let%test_unit "constraint: create_tuple with passing constraint" =
  with_storage (fun storage ->
    let db =
      match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false
      | Ok db -> db
    in
    let schema = Schema.empty |> Schema.add "value" "natural" in
    let db, _rel =
      match
        Manipulation.Memory.create_relation storage db ~name:"positives"
          ~schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Register a constraint: value must be member of natural (always true for naturals) *)
    let db =
      match
        Manipulation.Memory.register_constraint storage db
          ~constraint_name:"is_natural" ~relation_name:"positives"
          ~body:(Constraint.And [])
      with
      | Error _ -> assert false
      | Ok db -> db
    in
    let rel =
      match Manipulation.Memory.get_relation db ~name:"positives" with
      | None -> assert false
      | Some r -> r
    in
    let tuple : Tuple.materialized =
      {
        relation = "positives";
        attributes =
          Tuple.AttributeMap.singleton "value"
            { Attribute.value = Obj.repr 5 };
      }
    in
    match Manipulation.Memory.create_tuple storage db rel tuple with
    | Ok _ -> ()
    | Error _ -> assert false)

let%test_unit "constraint: create_tuple with failing constraint" =
  with_storage (fun storage ->
    let db =
      match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false
      | Ok db -> db
    in
    let schema = Schema.empty |> Schema.add "value" "natural" in
    let db, _rel =
      match
        Manipulation.Memory.create_relation storage db ~name:"checked"
          ~schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Register a constraint that always fails: MemberOf a nonexistent relation *)
    let db =
      match
        Manipulation.Memory.register_constraint storage db
          ~constraint_name:"impossible" ~relation_name:"checked"
          ~body:
            (Constraint.MemberOf
               {
                 target = "nonexistent_relation";
                 binding =
                   Constraint.BindingMap.singleton "x" (Constraint.Var "value");
               })
      with
      | Error _ -> assert false
      | Ok db -> db
    in
    let rel =
      match Manipulation.Memory.get_relation db ~name:"checked" with
      | None -> assert false
      | Some r -> r
    in
    let tuple : Tuple.materialized =
      {
        relation = "checked";
        attributes =
          Tuple.AttributeMap.singleton "value"
            { Attribute.value = Obj.repr 5 };
      }
    in
    match Manipulation.Memory.create_tuple storage db rel tuple with
    | Error (Manipulation.ConstraintViolation _) -> ()
    | _ -> assert false)

(* ---------- Scenario tests ported from Erlang ---------- *)

(* Scenario 1: Mutual exclusion between subtypes *)
let%test_unit "constraint scenario: mutual exclusion subtypes" =
  with_storage (fun storage ->
    let db =
      match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false
      | Ok db -> db
    in
    let schema = Schema.empty |> Schema.add "id" "natural" in
    let db, _employee =
      match
        Manipulation.Memory.create_relation storage db ~name:"employee"
          ~schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    let db, _manager =
      match
        Manipulation.Memory.create_relation storage db ~name:"manager"
          ~schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* manager must NOT be in employee (mutual exclusion) *)
    let body =
      Constraint.Not
        {
          body =
            Constraint.MemberOf
              {
                target = "employee";
                binding =
                  Constraint.BindingMap.singleton "id" (Constraint.Var "id");
              };
          universe = "manager";
        }
    in
    let db =
      match
        Manipulation.Memory.register_constraint storage db
          ~constraint_name:"not_employee" ~relation_name:"manager" ~body
      with
      | Error _ -> assert false
      | Ok db -> db
    in
    (* Insert into employee first *)
    let employee =
      match Manipulation.Memory.get_relation db ~name:"employee" with
      | None -> assert false
      | Some r -> r
    in
    let emp_tuple : Tuple.materialized =
      {
        relation = "employee";
        attributes =
          Tuple.AttributeMap.singleton "id"
            { Attribute.value = Obj.repr 1 };
      }
    in
    let db, _employee, _ =
      match
        Manipulation.Memory.create_tuple storage db employee emp_tuple
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Now try to insert same id into manager — should fail *)
    let manager =
      match Manipulation.Memory.get_relation db ~name:"manager" with
      | None -> assert false
      | Some r -> r
    in
    let mgr_tuple : Tuple.materialized =
      {
        relation = "manager";
        attributes =
          Tuple.AttributeMap.singleton "id"
            { Attribute.value = Obj.repr 1 };
      }
    in
    match Manipulation.Memory.create_tuple storage db manager mgr_tuple with
    | Error (Manipulation.ConstraintViolation _) -> ()
    | _ -> assert false)

(* Scenario 2: Foreign key constraint *)
let%test_unit "constraint scenario: foreign key" =
  with_storage (fun storage ->
    let db =
      match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false
      | Ok db -> db
    in
    let order_schema = Schema.empty |> Schema.add "order_id" "natural" in
    let db, _orders =
      match
        Manipulation.Memory.create_relation storage db ~name:"orders"
          ~schema:order_schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    let item_schema =
      Schema.empty |> Schema.add "item_id" "natural"
      |> Schema.add "order_id" "natural"
    in
    let db, _items =
      match
        Manipulation.Memory.create_relation storage db ~name:"order_items"
          ~schema:item_schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* FK: order_items.order_id must exist in orders *)
    let fk_body =
      Constraint.MemberOf
        {
          target = "orders";
          binding =
            Constraint.BindingMap.singleton "order_id"
              (Constraint.Var "order_id");
        }
    in
    let db =
      match
        Manipulation.Memory.register_constraint storage db
          ~constraint_name:"fk_order" ~relation_name:"order_items"
          ~body:fk_body
      with
      | Error _ -> assert false
      | Ok db -> db
    in
    (* Insert an order *)
    let orders =
      match Manipulation.Memory.get_relation db ~name:"orders" with
      | None -> assert false
      | Some r -> r
    in
    let order_tuple : Tuple.materialized =
      {
        relation = "orders";
        attributes =
          Tuple.AttributeMap.singleton "order_id"
            { Attribute.value = Obj.repr 100 };
      }
    in
    let db, _orders, _ =
      match
        Manipulation.Memory.create_tuple storage db orders order_tuple
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Insert item referencing valid order — should succeed *)
    let items =
      match Manipulation.Memory.get_relation db ~name:"order_items" with
      | None -> assert false
      | Some r -> r
    in
    let valid_item : Tuple.materialized =
      {
        relation = "order_items";
        attributes =
          Tuple.AttributeMap.of_list
            [
              ("item_id", { Attribute.value = Obj.repr 1 });
              ("order_id", { Attribute.value = Obj.repr 100 });
            ];
      }
    in
    let db, items, _ =
      match
        Manipulation.Memory.create_tuple storage db items valid_item
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Insert item referencing nonexistent order — should fail *)
    let invalid_item : Tuple.materialized =
      {
        relation = "order_items";
        attributes =
          Tuple.AttributeMap.of_list
            [
              ("item_id", { Attribute.value = Obj.repr 2 });
              ("order_id", { Attribute.value = Obj.repr 999 });
            ];
      }
    in
    match Manipulation.Memory.create_tuple storage db items invalid_item with
    | Error (Manipulation.ConstraintViolation _) -> ()
    | _ -> assert false)

(* Scenario 3: Self-reference (emp_id != mgr_id via not_equal comparison) *)
let%test_unit "constraint scenario: self-reference neq" =
  with_storage (fun storage ->
    let db =
      match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false
      | Ok db -> db
    in
    let schema =
      Schema.empty |> Schema.add "emp_id" "natural"
      |> Schema.add "mgr_id" "natural"
    in
    let db, _rel =
      match
        Manipulation.Memory.create_relation storage db ~name:"reports_to"
          ~schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Register the not_equal comparison relation *)
    let db, _ =
      match
        Manipulation.Memory.create_immutable_relation storage db
          ~name:"not_equal"
          ~schema:
            (Schema.empty |> Schema.add "left" "natural"
            |> Schema.add "right" "natural")
          ~generator:(fun _ -> Generator.Error "not enumerable")
          ~membership_criteria:(fun t ->
            match t with
            | Tuple.Materialized m -> (
              match
                ( Tuple.AttributeMap.find_opt "left" m.attributes,
                  Tuple.AttributeMap.find_opt "right" m.attributes )
              with
              | Some l, Some r ->
                (Obj.obj l.Attribute.value : int)
                <> (Obj.obj r.Attribute.value : int)
              | _ -> false)
            | _ -> false)
          ~cardinality:Conventions.Cardinality.AlephZero
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Constraint: emp_id != mgr_id via not_equal relation *)
    let neq_body =
      Constraint.neq ~left:(Var "emp_id") ~right:(Var "mgr_id")
    in
    let db =
      match
        Manipulation.Memory.register_constraint storage db
          ~constraint_name:"no_self_manage" ~relation_name:"reports_to"
          ~body:neq_body
      with
      | Error _ -> assert false
      | Ok db -> db
    in
    let rel =
      match Manipulation.Memory.get_relation db ~name:"reports_to" with
      | None -> assert false
      | Some r -> r
    in
    (* Insert (emp_id=1, mgr_id=2) — should succeed *)
    let valid : Tuple.materialized =
      {
        relation = "reports_to";
        attributes =
          Tuple.AttributeMap.of_list
            [
              ("emp_id", { Attribute.value = Obj.repr 1 });
              ("mgr_id", { Attribute.value = Obj.repr 2 });
            ];
      }
    in
    let db, rel, _ =
      match Manipulation.Memory.create_tuple storage db rel valid with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Insert (emp_id=3, mgr_id=3) — same person, should fail *)
    let invalid : Tuple.materialized =
      {
        relation = "reports_to";
        attributes =
          Tuple.AttributeMap.of_list
            [
              ("emp_id", { Attribute.value = Obj.repr 3 });
              ("mgr_id", { Attribute.value = Obj.repr 3 });
            ];
      }
    in
    match Manipulation.Memory.create_tuple storage db rel invalid with
    | Error (Manipulation.ConstraintViolation _) -> ()
    | _ -> assert false)

(* Scenario 4: Mutual exclusion between open_ticket and closed_ticket *)
let%test_unit "constraint scenario: open vs closed ticket" =
  with_storage (fun storage ->
    let db =
      match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false
      | Ok db -> db
    in
    let schema = Schema.empty |> Schema.add "ticket_id" "natural" in
    let db, _ =
      match
        Manipulation.Memory.create_relation storage db ~name:"open_ticket"
          ~schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    let db, _ =
      match
        Manipulation.Memory.create_relation storage db ~name:"closed_ticket"
          ~schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* open_ticket must not be in closed_ticket *)
    let db =
      match
        Manipulation.Memory.register_constraint storage db
          ~constraint_name:"not_closed" ~relation_name:"open_ticket"
          ~body:
            (Constraint.Not
               {
                 body =
                   Constraint.MemberOf
                     {
                       target = "closed_ticket";
                       binding =
                         Constraint.BindingMap.singleton "ticket_id"
                           (Constraint.Var "ticket_id");
                     };
                 universe = "open_ticket";
               })
      with
      | Error _ -> assert false
      | Ok db -> db
    in
    (* Insert ticket 1 as closed *)
    let closed =
      match Manipulation.Memory.get_relation db ~name:"closed_ticket" with
      | None -> assert false
      | Some r -> r
    in
    let t1 : Tuple.materialized =
      {
        relation = "closed_ticket";
        attributes =
          Tuple.AttributeMap.singleton "ticket_id"
            { Attribute.value = Obj.repr 1 };
      }
    in
    let db, _, _ =
      match Manipulation.Memory.create_tuple storage db closed t1 with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Try to open same ticket — should fail *)
    let open_ =
      match Manipulation.Memory.get_relation db ~name:"open_ticket" with
      | None -> assert false
      | Some r -> r
    in
    let t1_open : Tuple.materialized =
      {
        relation = "open_ticket";
        attributes =
          Tuple.AttributeMap.singleton "ticket_id"
            { Attribute.value = Obj.repr 1 };
      }
    in
    match Manipulation.Memory.create_tuple storage db open_ t1_open with
    | Error (Manipulation.ConstraintViolation _) -> ()
    | _ -> assert false)

(* Scenario 5: Weak entity dependency *)
let%test_unit "constraint scenario: weak entity dependency" =
  with_storage (fun storage ->
    let db =
      match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false
      | Ok db -> db
    in
    let parent_schema = Schema.empty |> Schema.add "parent_id" "natural" in
    let db, _ =
      match
        Manipulation.Memory.create_relation storage db ~name:"parent"
          ~schema:parent_schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    let dep_schema =
      Schema.empty |> Schema.add "dep_id" "natural"
      |> Schema.add "parent_id" "natural"
    in
    let db, _ =
      match
        Manipulation.Memory.create_relation storage db ~name:"dependent"
          ~schema:dep_schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* dependent.parent_id must exist in parent *)
    let db =
      match
        Manipulation.Memory.register_constraint storage db
          ~constraint_name:"parent_exists" ~relation_name:"dependent"
          ~body:
            (Constraint.MemberOf
               {
                 target = "parent";
                 binding =
                   Constraint.BindingMap.singleton "parent_id"
                     (Constraint.Var "parent_id");
               })
      with
      | Error _ -> assert false
      | Ok db -> db
    in
    (* Insert parent *)
    let parent =
      match Manipulation.Memory.get_relation db ~name:"parent" with
      | None -> assert false
      | Some r -> r
    in
    let pt : Tuple.materialized =
      {
        relation = "parent";
        attributes =
          Tuple.AttributeMap.singleton "parent_id"
            { Attribute.value = Obj.repr 10 };
      }
    in
    let db, _, _ =
      match Manipulation.Memory.create_tuple storage db parent pt with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Insert dependent with valid parent — succeeds *)
    let dep =
      match Manipulation.Memory.get_relation db ~name:"dependent" with
      | None -> assert false
      | Some r -> r
    in
    let valid_dep : Tuple.materialized =
      {
        relation = "dependent";
        attributes =
          Tuple.AttributeMap.of_list
            [
              ("dep_id", { Attribute.value = Obj.repr 1 });
              ("parent_id", { Attribute.value = Obj.repr 10 });
            ];
      }
    in
    let db, dep, _ =
      match
        Manipulation.Memory.create_tuple storage db dep valid_dep
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Insert dependent with nonexistent parent — fails *)
    let invalid_dep : Tuple.materialized =
      {
        relation = "dependent";
        attributes =
          Tuple.AttributeMap.of_list
            [
              ("dep_id", { Attribute.value = Obj.repr 2 });
              ("parent_id", { Attribute.value = Obj.repr 999 });
            ];
      }
    in
    match
      Manipulation.Memory.create_tuple storage db dep invalid_dep
    with
    | Error (Manipulation.ConstraintViolation _) -> ()
    | _ -> assert false)

(* Scenario 6: Algebra propagation — select preserves constraints *)
let%test_unit "constraint propagation: select preserves constraints" =
  with_storage (fun storage ->
    let db =
      match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false
      | Ok db -> db
    in
    let schema = Schema.empty |> Schema.add "x" "natural" in
    let db, _rel =
      match
        Manipulation.Memory.create_relation storage db ~name:"constrained"
          ~schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    let db =
      match
        Manipulation.Memory.register_constraint storage db
          ~constraint_name:"c1" ~relation_name:"constrained"
          ~body:(Constraint.And [])
      with
      | Error _ -> assert false
      | Ok db -> db
    in
    let rel =
      match Manipulation.Memory.get_relation db ~name:"constrained" with
      | None -> assert false
      | Some r -> r
    in
    match
      Algebra.Memory.select_fn storage (fun _ -> true) rel
    with
    | Error _ -> assert false
    | Ok result ->
      assert (result.Relation.constraints <> None))

(* Scenario 7: Algebra propagation — project filters constraints *)
let%test_unit "constraint propagation: project filters constraints" =
  with_storage (fun storage ->
    let db =
      match Manipulation.Memory.create_database storage ~name:"test" with
      | Error _ -> assert false
      | Ok db -> db
    in
    let schema =
      Schema.empty |> Schema.add "x" "natural" |> Schema.add "y" "natural"
    in
    let db, _rel =
      match
        Manipulation.Memory.create_relation storage db ~name:"xy" ~schema
      with
      | Error _ -> assert false
      | Ok x -> x
    in
    (* Constraint on x only *)
    let c_on_x =
      Constraint.MemberOf
        {
          target = "some_rel";
          binding =
            Constraint.BindingMap.singleton "left" (Constraint.Var "x");
        }
    in
    let db =
      match
        Manipulation.Memory.register_constraint storage db
          ~constraint_name:"x_only" ~relation_name:"xy" ~body:c_on_x
      with
      | Error _ -> assert false
      | Ok db -> db
    in
    let rel =
      match Manipulation.Memory.get_relation db ~name:"xy" with
      | None -> assert false
      | Some r -> r
    in
    (* Project to only "x" — constraint should survive *)
    (match Algebra.Memory.project storage [ "x" ] rel with
     | Error _ -> assert false
     | Ok result -> assert (result.Relation.constraints <> None));
    (* Project to only "y" — constraint referencing "x" should be dropped *)
    match Algebra.Memory.project storage [ "y" ] rel with
    | Error _ -> assert false
    | Ok result -> assert (result.Relation.constraints = None))

(* ============================================================================
   DML Sublanguage Tests
   ============================================================================ *)

(* Parse tests use canonical flat sexp format: (Constructor (field val) ...) *)

let%test_unit "dml: parse CreateDatabase" =
  match Dml.Parser.of_string {|(CreateDatabase "shop")|} with
  | Error _ -> assert false
  | Ok stmt -> assert (stmt = Dml.Ast.CreateDatabase "shop")

let%test_unit "dml: parse RetractRelation" =
  match Dml.Parser.of_string {|(RetractRelation "users")|} with
  | Error _ -> assert false
  | Ok stmt -> assert (stmt = Dml.Ast.RetractRelation "users")

let%test_unit "dml: parse ClearRelation" =
  match Dml.Parser.of_string {|(ClearRelation "users")|} with
  | Error _ -> assert false
  | Ok stmt -> assert (stmt = Dml.Ast.ClearRelation "users")

let%test_unit "dml: round-trip InsertTuple" =
  let src = Dml.Ast.InsertTuple {
    relation = "users";
    attributes = [("name", Drl.Ast.Str "Alice"); ("age", Drl.Ast.Int 30)]
  } in
  match Dml.Parser.of_string (Dml.Parser.to_string src) with
  | Error _ -> assert false
  | Ok parsed -> assert (parsed = src)

let%test_unit "dml: round-trip CreateRelation" =
  let src = Dml.Ast.CreateRelation {
    name = "users";
    schema = [("name", "string"); ("age", "natural")]
  } in
  match Dml.Parser.of_string (Dml.Parser.to_string src) with
  | Error _ -> assert false
  | Ok parsed -> assert (parsed = src)

let%test_unit "dml: round-trip InsertTuples" =
  let src = Dml.Ast.InsertTuples {
    relation = "users";
    tuples = [
      [("name", Drl.Ast.Str "Alice"); ("age", Drl.Ast.Int 30)];
      [("name", Drl.Ast.Str "Bob");   ("age", Drl.Ast.Int 25)];
    ]
  } in
  match Dml.Parser.of_string (Dml.Parser.to_string src) with
  | Error _ -> assert false
  | Ok parsed -> assert (parsed = src)

let%test_unit "dml: round-trip RegisterDomain" =
  let src = Dml.Ast.RegisterDomain { name = "money"; cardinality = Dml.Ast.AlephZero } in
  match Dml.Parser.of_string (Dml.Parser.to_string src) with
  | Error _ -> assert false
  | Ok parsed -> assert (parsed = src)

(* Executor tests construct AST directly — no dependency on sexp format *)

let%test_unit "dml: execute CreateDatabase" =
  with_storage (fun storage ->
    let db = Management.Database.empty ~name:"" in
    let stmt = Dml.Ast.CreateDatabase "shop" in
    match Dml.Executor.Memory.execute storage db stmt with
    | Error _ -> assert false
    | Ok db -> assert (db.name = "shop"))

let%test_unit "dml: execute CreateRelation" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in
    let stmt = Dml.Ast.CreateRelation { name = "users"; schema = [("name", "string"); ("age", "natural")] } in
    match Dml.Executor.Memory.execute storage db stmt with
    | Error _ -> assert false
    | Ok db -> assert (Management.Database.has_relation db "users"))

let%test_unit "dml: execute InsertTuple" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty |> Schema.add "name" "string" in
    let db = match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
      | Error _ -> assert false | Ok (db, _) -> db
    in
    let stmt = Dml.Ast.InsertTuple { relation = "users"; attributes = [("name", Drl.Ast.Str "Alice")] } in
    match Dml.Executor.Memory.execute storage db stmt with
    | Error _ -> assert false
    | Ok db ->
      let rel = match Management.Database.get_relation db "users" with
        | None -> assert false | Some r -> r
      in
      assert (Manipulation.Memory.tuple_count rel = 1))

let%test_unit "dml: execute InsertTuples" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty |> Schema.add "name" "string" in
    let db = match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
      | Error _ -> assert false | Ok (db, _) -> db
    in
    let stmt = Dml.Ast.InsertTuples {
      relation = "users";
      tuples = [[("name", Drl.Ast.Str "Alice")]; [("name", Drl.Ast.Str "Bob")]]
    } in
    match Dml.Executor.Memory.execute storage db stmt with
    | Error _ -> assert false
    | Ok db ->
      let rel = match Management.Database.get_relation db "users" with
        | None -> assert false | Some r -> r
      in
      assert (Manipulation.Memory.tuple_count rel = 2))

let%test_unit "dml: execute DeleteTuple" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty |> Schema.add "name" "string" in
    let db = match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
      | Error _ -> assert false | Ok (db, _) -> db
    in
    let db = match Dml.Executor.Memory.execute storage db
      (Dml.Ast.InsertTuple { relation = "users"; attributes = [("name", Drl.Ast.Str "Alice")] }) with
      | Error _ -> assert false | Ok db -> db
    in
    let stmt = Dml.Ast.DeleteTuple { relation = "users"; attributes = [("name", Drl.Ast.Str "Alice")] } in
    match Dml.Executor.Memory.execute storage db stmt with
    | Error _ -> assert false
    | Ok db ->
      let rel = match Management.Database.get_relation db "users" with
        | None -> assert false | Some r -> r
      in
      assert (Manipulation.Memory.tuple_count rel = 0))

let%test_unit "dml: execute RetractRelation" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty in
    let db = match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
      | Error _ -> assert false | Ok (db, _) -> db
    in
    match Dml.Executor.Memory.execute storage db (Dml.Ast.RetractRelation "users") with
    | Error _ -> assert false
    | Ok db -> assert (not (Management.Database.has_relation db "users")))

let%test_unit "dml: execute ClearRelation" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty |> Schema.add "name" "string" in
    let db = match Manipulation.Memory.create_relation storage db ~name:"users" ~schema with
      | Error _ -> assert false | Ok (db, _) -> db
    in
    let db = match Dml.Executor.Memory.execute storage db
      (Dml.Ast.InsertTuples { relation = "users";
        tuples = [[("name", Drl.Ast.Str "Alice")]; [("name", Drl.Ast.Str "Bob")]] }) with
      | Error _ -> assert false | Ok db -> db
    in
    match Dml.Executor.Memory.execute storage db (Dml.Ast.ClearRelation "users") with
    | Error _ -> assert false
    | Ok db ->
      let rel = match Management.Database.get_relation db "users" with
        | None -> assert false | Some r -> r
      in
      assert (Manipulation.Memory.tuple_count rel = 0))

let%test_unit "dml: execute RegisterDomain" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in
    let stmt = Dml.Ast.RegisterDomain { name = "money"; cardinality = Dml.Ast.AlephZero } in
    match Dml.Executor.Memory.execute storage db stmt with
    | Error _ -> assert false
    | Ok db -> assert (Management.Database.has_domain db "money"))

let%test_unit "dml: insert into nonexistent relation returns error" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in
    let stmt = Dml.Ast.InsertTuple { relation = "ghost"; attributes = [("x", Drl.Ast.Int 1)] } in
    match Dml.Executor.Memory.execute storage db stmt with
    | Error (Dml.Executor.Memory.RelationNotFound "ghost") -> ()
    | _ -> assert false)

(* ============================================================================
   DCL Sublanguage Tests
   ============================================================================ *)

let%test_unit "dcl: round-trip RegisterConstraint MemberOf" =
  let src = Dcl.Ast.RegisterConstraint {
    constraint_name = "fk_order";
    relation_name = "order_items";
    body = Dcl.Ast.MemberOf { target = "orders"; binding = [("order_id", Dcl.Ast.Var "order_id")] }
  } in
  match Dcl.Parser.of_string (Dcl.Parser.to_string src) with
  | Error _ -> assert false
  | Ok parsed -> assert (parsed = src)

let%test_unit "dcl: round-trip And constraint" =
  let src = Dcl.Ast.RegisterConstraint {
    constraint_name = "valid_range";
    relation_name = "scores";
    body = Dcl.Ast.And [
      Dcl.Ast.MemberOf { target = "ge_zero";
        binding = [("left", Dcl.Ast.Var "score"); ("right", Dcl.Ast.Const (Drl.Ast.Int 0))] };
      Dcl.Ast.MemberOf { target = "le_hundred";
        binding = [("left", Dcl.Ast.Var "score"); ("right", Dcl.Ast.Const (Drl.Ast.Int 100))] };
    ]
  } in
  match Dcl.Parser.of_string (Dcl.Parser.to_string src) with
  | Error _ -> assert false
  | Ok parsed -> assert (parsed = src)

let%test_unit "dcl: round-trip Not constraint" =
  let src = Dcl.Ast.RegisterConstraint {
    constraint_name = "not_closed";
    relation_name = "open_ticket";
    body = Dcl.Ast.Not {
      body = Dcl.Ast.MemberOf { target = "closed_ticket";
        binding = [("ticket_id", Dcl.Ast.Var "ticket_id")] };
      universe = "open_ticket"
    }
  } in
  match Dcl.Parser.of_string (Dcl.Parser.to_string src) with
  | Error _ -> assert false
  | Ok parsed -> assert (parsed = src)

let%test_unit "dcl: execute RegisterConstraint attaches constraint" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in
    let schema = Schema.empty |> Schema.add "order_id" "natural" in
    let db = match Manipulation.Memory.create_relation storage db ~name:"order_items" ~schema with
      | Error _ -> assert false | Ok (db, _) -> db
    in
    let stmt = Dcl.Ast.RegisterConstraint {
      constraint_name = "fk_order";
      relation_name = "order_items";
      body = Dcl.Ast.MemberOf { target = "orders"; binding = [("order_id", Dcl.Ast.Var "order_id")] }
    } in
    match Dcl.Executor.Memory.execute storage db stmt with
    | Error _ -> assert false
    | Ok db ->
      let rel = match Management.Database.get_relation db "order_items" with
        | None -> assert false | Some r -> r
      in
      assert (rel.Relation.constraints <> None))

let%test_unit "dcl: FK constraint enforced on insert" =
  with_storage (fun storage ->
    let db = match Manipulation.Memory.create_database storage ~name:"shop" with
      | Error _ -> assert false | Ok db -> db
    in
    let db = match Manipulation.Memory.create_relation storage db ~name:"orders"
        ~schema:(Schema.empty |> Schema.add "id" "natural") with
      | Error _ -> assert false | Ok (db, _) -> db
    in
    (* Insert a valid order *)
    let db = match Dml.Executor.Memory.execute storage db
      (Dml.Ast.InsertTuple { relation = "orders"; attributes = [("id", Drl.Ast.Int 1)] }) with
      | Error _ -> assert false | Ok db -> db
    in
    let db = match Manipulation.Memory.create_relation storage db ~name:"order_items"
        ~schema:(Schema.empty |> Schema.add "order_id" "natural") with
      | Error _ -> assert false | Ok (db, _) -> db
    in
    (* Register FK: order_id in order_items must match id in orders *)
    let db = match Dcl.Executor.Memory.execute storage db
      (Dcl.Ast.RegisterConstraint {
        constraint_name = "fk_order";
        relation_name = "order_items";
        body = Dcl.Ast.MemberOf { target = "orders"; binding = [("id", Dcl.Ast.Var "order_id")] }
      }) with
      | Error _ -> assert false | Ok db -> db
    in
    (* Valid insert: order_id=1 exists in orders *)
    let db = match Dml.Executor.Memory.execute storage db
      (Dml.Ast.InsertTuple { relation = "order_items"; attributes = [("order_id", Drl.Ast.Int 1)] }) with
      | Error _ -> assert false | Ok db -> db
    in
    let rel = match Management.Database.get_relation db "order_items" with
      | None -> assert false | Some r -> r
    in
    assert (Manipulation.Memory.tuple_count rel = 1);
    (* Invalid insert: order_id=99 does not exist in orders *)
    match Dml.Executor.Memory.execute storage db
      (Dml.Ast.InsertTuple { relation = "order_items"; attributes = [("order_id", Drl.Ast.Int 99)] }) with
    | Error (Dml.Executor.Memory.ManipulationError (Manipulation.ConstraintViolation _)) -> ()
    | _ -> assert false)