Add tests for ID scalar with Guid values

Agent-Logs-Url: https://github.com/fsprojects/FSharp.Data.GraphQL/sessions/d2fe5523-e81b-4d08-813e-b7f106345347

Co-authored-by: xperiandri <2365592+xperiandri@users.noreply.github.com>

Author: Copilot

tests/FSharp.Data.GraphQL.Tests/ExecutionTests.fs

@@ -603,3 +603,73 @@ let ``Execution handles errors: additional error added and when null returned fr
     ensureRequestError result <| fun errors ->
         result.DocumentId |> notEquals Unchecked.defaultof<int>
         errors |> equals expectedErrors
+
+type PersonWithGuidId =
+    { Id: Guid
+      Name: string }
+
+[<Fact>]
+let ``Execution handles ID scalar: serializes Guid field via AutoField`` () =
+    let id1 = Guid.Parse "d6c684d9-aaaa-4e88-bbb2-0bb584f1661d"
+    let id2 = Guid.Parse "d6c684d9-bbbb-4e88-bbb2-0bb584f1661d"
+    let people =
+        [ { Id = id1; Name = "Person A" }
+          { Id = id2; Name = "Person B" } ]
+
+    let PersonType =
+        Define.Object<PersonWithGuidId>(
+            "Person",
+            [ Define.AutoField("id", IDType)
+              Define.AutoField("name", StringType) ])
+
+    let QueryRoot =
+        Define.Object("Query",
+            [ Define.Field("people", ListOf PersonType, fun _ () -> people) ])
+
+    let schema = Schema(query = QueryRoot)
+    let executor = Executor(schema)
+
+    let result = sync <| executor.AsyncExecute("{people{id name}}", getMockInputContext)
+    let expected =
+        NameValueLookup.ofList [
+            "people", upcast [
+                box <| NameValueLookup.ofList [ "id", box (string id1); "name", box "Person A" ]
+                box <| NameValueLookup.ofList [ "id", box (string id2); "name", box "Person B" ]
+            ]
+        ]
+    ensureDirect result <| fun data errors ->
+        empty errors
+        data |> equals (upcast expected)
+
+[<Fact>]
+let ``Execution handles ID scalar: serializes Guid field via explicit Field resolve`` () =
+    let id1 = Guid.Parse "d6c684d9-aaaa-4e88-bbb2-0bb584f1661d"
+    let id2 = Guid.Parse "d6c684d9-bbbb-4e88-bbb2-0bb584f1661d"
+    let people =
+        [ { Id = id1; Name = "Person A" }
+          { Id = id2; Name = "Person B" } ]
+
+    let PersonType =
+        Define.Object<PersonWithGuidId>(
+            "Person",
+            [ Define.Field("id", IDType, fun _ (p : PersonWithGuidId) -> string p.Id)
+              Define.AutoField("name", StringType) ])
+
+    let QueryRoot =
+        Define.Object("Query",
+            [ Define.Field("people", ListOf PersonType, fun _ () -> people) ])
+
+    let schema = Schema(query = QueryRoot)
+    let executor = Executor(schema)
+
+    let result = sync <| executor.AsyncExecute("{people{id name}}", getMockInputContext)
+    let expected =
+        NameValueLookup.ofList [
+            "people", upcast [
+                box <| NameValueLookup.ofList [ "id", box (string id1); "name", box "Person A" ]
+                box <| NameValueLookup.ofList [ "id", box (string id2); "name", box "Person B" ]
+            ]
+        ]
+    ensureDirect result <| fun data errors ->
+        empty errors
+        data |> equals (upcast expected)

tests/FSharp.Data.GraphQL.Tests/Variables and Inputs/CoercionTests.fs

@@ -112,3 +112,17 @@ let ``ID coerces input`` () =
     // We have no idea that it is an enum
     testCoercion IDType "enum" (Variable (JsonDocument.Parse "\"enum\"").RootElement)
     testCoercionError IDType "Inline value 'enum' of type enum cannot be converted into identifier" (InlineConstant (EnumValue "enum"))
+
+let private testOutputCoercion graphQLType (expected: 'a) (input: obj) =
+    let (Scalar scalar) = graphQLType
+    match scalar.CoerceOutput input with
+    | Some actual -> equals (box expected) actual
+    | None -> Assert.Fail $"Expected CoerceOutput of %A{input} to return Some but got None"
+
+[<Fact>]
+let ``ID coerces output`` () =
+    testOutputCoercion IDType "abc" ("abc" : obj)
+    testOutputCoercion IDType "123" (123 : obj)
+    testOutputCoercion IDType "123" (123L : obj)
+    let guid = Guid.Parse "d6c684d9-aaaa-4e88-bbb2-0bb584f1661d"
+    testOutputCoercion IDType (string guid) (guid : obj)