Add more null-check tests, null-source should raise immediately, not after MoveNext

Author: abelbraaksma

src/FSharp.Control.TaskSeq.Test/Nunit.Extensions.fs

@@ -169,3 +169,6 @@ module ExtraCustomMatchers =
             $"Throws %s{ex.Name} (Below, XUnit does not show actual value properly)",
             (fun fn -> (testForThrowing (fn :?> (unit -> Task))).Result)
         )
+
+    let inline assertThrows ty (f: unit -> 'U) = f >> ignore |> should throw ty
+    let inline assertNullArg f = assertThrows typeof<ArgumentNullException> f

src/FSharp.Control.TaskSeq.Test/TaskSeq.Append.Tests.fs

@@ -22,14 +22,17 @@ let validateSequence ts =
     |> Task.map (String.concat "")
     |> Task.map (should equal "1234567891012345678910")
 
+
 module EmptySeq =
+    [<Fact>]
     let ``Null source is invalid`` () =
-        let test1 () = TaskSeq.empty |> TaskSeq.append null |> TaskSeq.toList
-        let test2 () = null |> TaskSeq.append TaskSeq.empty |> TaskSeq.toList
-        let test3 () = null |> TaskSeq.append null |> TaskSeq.toList
-        test1 |> should throw typeof<ArgumentNullException>
-        test2 |> should throw typeof<ArgumentNullException>
-        test3 |> should throw typeof<ArgumentNullException>
+        assertNullArg
+        <| fun () -> TaskSeq.empty |> TaskSeq.append null
+
+        assertNullArg
+        <| fun () -> null |> TaskSeq.append TaskSeq.empty
+
+        assertNullArg <| fun () -> null |> TaskSeq.append null
 
     [<Theory; ClassData(typeof<TestEmptyVariants>)>]
     let ``TaskSeq-append both args empty`` variant =

src/FSharp.Control.TaskSeq.Test/TaskSeq.Cast.Tests.fs

@@ -23,6 +23,9 @@ let validateSequence ts =
     |> Task.map (should equal "12345678910")
 
 module EmptySeq =
+    [<Fact>]
+    let ``Null source is invalid`` () = assertNullArg <| fun () -> TaskSeq.box null
+
     [<Theory; ClassData(typeof<TestEmptyVariants>)>]
     let ``TaskSeq-box empty`` variant = Gen.getEmptyVariant variant |> TaskSeq.box |> verifyEmpty
 

src/FSharp.Control.TaskSeq.Test/TaskSeq.Choose.Tests.fs

@@ -10,13 +10,19 @@ open FsToolkit.ErrorHandling
 open FSharp.Control
 
 //
-// TaskSeq.map
-// TaskSeq.mapi
-// TaskSeq.mapAsync
-// TaskSeq.mapiAsync
+// TaskSeq.choose
+// TaskSeq.chooseAsync
 //
 
 module EmptySeq =
+    [<Fact>]
+    let ``Null source is invalid`` () =
+        assertNullArg
+        <| fun () -> TaskSeq.choose (fun _ -> None) null
+
+        assertNullArg
+        <| fun () -> TaskSeq.chooseAsync (fun _ -> Task.fromResult None) null
+
     [<Theory; ClassData(typeof<TestEmptyVariants>)>]
     let ``TaskSeq-choose`` variant = task {
         let! empty =

src/FSharp.Control.TaskSeq.Test/TaskSeq.Collect.Tests.fs

@@ -12,6 +12,13 @@ open FSharp.Control
 //
 
 module EmptySeq =
+    [<Fact>]
+    let ``Null source is invalid`` () =
+        assertNullArg
+        <| fun () -> TaskSeq.collect (fun _ -> TaskSeq.empty) null
+
+        assertNullArg
+        <| fun () -> TaskSeq.collectAsync (fun _ -> Task.fromResult TaskSeq.empty) null
 
     [<Theory; ClassData(typeof<TestEmptyVariants>)>]
     let ``TaskSeq-collect collecting emptiness`` variant =

src/FSharp.Control.TaskSeq.Test/TaskSeq.Concat.Tests.fs

@@ -21,6 +21,9 @@ let validateSequence ts =
     |> Task.map (should equal "123456789101234567891012345678910")
 
 module EmptySeq =
+    [<Fact>]
+    let ``Null source is invalid`` () = assertNullArg <| fun () -> TaskSeq.concat null
+
     [<Theory; ClassData(typeof<TestEmptyVariants>)>]
     let ``TaskSeq-concat with empty sequences`` variant =
         taskSeq {

src/FSharp.Control.TaskSeq.Test/TaskSeq.Contains.Tests.fs

@@ -11,6 +11,9 @@ open FSharp.Control
 //
 
 module EmptySeq =
+    [<Fact>]
+    let ``Null source is invalid`` () = assertNullArg <| fun () -> TaskSeq.contains 42 null
+
     [<Theory; ClassData(typeof<TestEmptyVariants>)>]
     let ``TaskSeq-contains returns false`` variant =
         Gen.getEmptyVariant variant

src/FSharp.Control.TaskSeq.Test/TaskSeq.Using.Tests.fs

@@ -1,4 +1,4 @@
-module TaskSeq.Test.Using
+module TaskSeq.Tests.Using
 
 open System
 open System.Threading.Tasks