From 1129aadc942e99154f53371417bebbe5a09184dc Mon Sep 17 00:00:00 2001
From: Abel Braaksma <abel.online@xs4all.nl>
Date: Wed, 20 Dec 2023 23:27:34 +0100
Subject: [PATCH] Add/update tests for `where` and `whereAsync`

---
 .../TaskSeq.Filter.Tests.fs                   | 119 ++++++++++++------
 src/FSharp.Control.TaskSeq.Test/TestUtils.fs  |   7 ++
 2 files changed, 87 insertions(+), 39 deletions(-)

diff --git a/src/FSharp.Control.TaskSeq.Test/TaskSeq.Filter.Tests.fs b/src/FSharp.Control.TaskSeq.Test/TaskSeq.Filter.Tests.fs
index fb67ad9f..0e189cc5 100644
--- a/src/FSharp.Control.TaskSeq.Test/TaskSeq.Filter.Tests.fs
+++ b/src/FSharp.Control.TaskSeq.Test/TaskSeq.Filter.Tests.fs
@@ -10,67 +10,108 @@ open FSharp.Control
 //
 // TaskSeq.filter
 // TaskSeq.filterAsync
+// TaskSeq.where
+// TaskSeq.whereAsync
 //
 
 
 module EmptySeq =
     [<Fact>]
-    let ``Null source is invalid`` () =
+    let ``TaskSeq-filter or where with null source raises`` () =
         assertNullArg
         <| fun () -> TaskSeq.filter (fun _ -> false) null
 
         assertNullArg
         <| fun () -> TaskSeq.filterAsync (fun _ -> Task.fromResult false) null
 
+        assertNullArg
+        <| fun () -> TaskSeq.where (fun _ -> false) null
+
+        assertNullArg
+        <| fun () -> TaskSeq.whereAsync (fun _ -> Task.fromResult false) null
+
 
     [<Theory; ClassData(typeof<TestEmptyVariants>)>]
-    let ``TaskSeq-filter has no effect`` variant =
-        Gen.getEmptyVariant variant
-        |> TaskSeq.filter ((=) 12)
-        |> TaskSeq.toListAsync
-        |> Task.map (List.isEmpty >> should be True)
+    let ``TaskSeq-filter or where has no effect`` variant = task {
+        do!
+            Gen.getEmptyVariant variant
+            |> TaskSeq.filter ((=) 12)
+            |> TaskSeq.toListAsync
+            |> Task.map (List.isEmpty >> should be True)
+
+        do!
+            Gen.getEmptyVariant variant
+            |> TaskSeq.where ((=) 12)
+            |> TaskSeq.toListAsync
+            |> Task.map (List.isEmpty >> should be True)
+    }
 
     [<Theory; ClassData(typeof<TestEmptyVariants>)>]
-    let ``TaskSeq-filterAsync has no effect`` variant =
-        Gen.getEmptyVariant variant
-        |> TaskSeq.filterAsync (fun x -> task { return x = 12 })
-        |> TaskSeq.toListAsync
-        |> Task.map (List.isEmpty >> should be True)
+    let ``TaskSeq-filterAsync or whereAsync has no effect`` variant = task {
+        do!
+            Gen.getEmptyVariant variant
+            |> TaskSeq.filterAsync (fun x -> task { return x = 12 })
+            |> TaskSeq.toListAsync
+            |> Task.map (List.isEmpty >> should be True)
+
+        do!
+            Gen.getEmptyVariant variant
+            |> TaskSeq.whereAsync (fun x -> task { return x = 12 })
+            |> TaskSeq.toListAsync
+            |> Task.map (List.isEmpty >> should be True)
+    }
 
 module Immutable =
     [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
-    let ``TaskSeq-filter filters correctly`` variant =
-        Gen.getSeqImmutable variant
-        |> TaskSeq.filter ((<=) 5) // greater than
-        |> TaskSeq.map char
-        |> TaskSeq.map ((+) '@')
-        |> TaskSeq.toArrayAsync
-        |> Task.map (String >> should equal "EFGHIJ")
+    let ``TaskSeq-filter or where filters correctly`` variant = task {
+        do!
+            Gen.getSeqImmutable variant
+            |> TaskSeq.filter ((<=) 5) // greater than
+            |> verifyDigitsAsString "EFGHIJ"
+
+        do!
+            Gen.getSeqImmutable variant
+            |> TaskSeq.where ((>) 5) // greater than
+            |> verifyDigitsAsString "ABCD"
+    }
 
     [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
-    let ``TaskSeq-filterAsync filters correctly`` variant =
-        Gen.getSeqImmutable variant
-        |> TaskSeq.filterAsync (fun x -> task { return x <= 5 })
-        |> TaskSeq.map char
-        |> TaskSeq.map ((+) '@')
-        |> TaskSeq.toArrayAsync
-        |> Task.map (String >> should equal "ABCDE")
+    let ``TaskSeq-filterAsync or whereAsync filters correctly`` variant = task {
+        do!
+            Gen.getSeqImmutable variant
+            |> TaskSeq.filterAsync (fun x -> task { return x <= 5 })
+            |> verifyDigitsAsString "ABCDE"
+
+        do!
+            Gen.getSeqImmutable variant
+            |> TaskSeq.whereAsync (fun x -> task { return x > 5 })
+            |> verifyDigitsAsString "FGHIJ"
+
+    }
 
 module SideEffects =
     [<Theory; ClassData(typeof<TestSideEffectTaskSeq>)>]
-    let ``TaskSeq-filter filters correctly`` variant =
-        Gen.getSeqWithSideEffect variant
-        |> TaskSeq.filter ((<=) 5) // greater than
-        |> TaskSeq.map char
-        |> TaskSeq.map ((+) '@')
-        |> TaskSeq.toArrayAsync
-        |> Task.map (String >> should equal "EFGHIJ")
+    let ``TaskSeq-filter filters correctly`` variant = task {
+        do!
+            Gen.getSeqWithSideEffect variant
+            |> TaskSeq.filter ((<=) 5) // greater than or equal
+            |> verifyDigitsAsString "EFGHIJ"
+
+        do!
+            Gen.getSeqWithSideEffect variant
+            |> TaskSeq.where ((>) 5) // less than
+            |> verifyDigitsAsString "ABCD"
+    }
 
     [<Theory; ClassData(typeof<TestSideEffectTaskSeq>)>]
-    let ``TaskSeq-filterAsync filters correctly`` variant =
-        Gen.getSeqWithSideEffect variant
-        |> TaskSeq.filterAsync (fun x -> task { return x <= 5 })
-        |> TaskSeq.map char
-        |> TaskSeq.map ((+) '@')
-        |> TaskSeq.toArrayAsync
-        |> Task.map (String >> should equal "ABCDE")
+    let ``TaskSeq-filterAsync filters correctly`` variant = task {
+        do!
+            Gen.getSeqWithSideEffect variant
+            |> TaskSeq.filterAsync (fun x -> task { return x <= 5 })
+            |> verifyDigitsAsString "ABCDE"
+
+        do!
+            Gen.getSeqWithSideEffect variant
+            |> TaskSeq.whereAsync (fun x -> task { return x > 5 && x < 9 })
+            |> verifyDigitsAsString "FGH"
+    }
diff --git a/src/FSharp.Control.TaskSeq.Test/TestUtils.fs b/src/FSharp.Control.TaskSeq.Test/TestUtils.fs
index d8afe1b6..c98b4797 100644
--- a/src/FSharp.Control.TaskSeq.Test/TestUtils.fs
+++ b/src/FSharp.Control.TaskSeq.Test/TestUtils.fs
@@ -141,6 +141,13 @@ module TestUtils =
         |> TaskSeq.toArrayAsync
         |> Task.map (should equal [| 1..10 |])
 
+    /// Turns a sequence of numbers into a string, starting with A for '1'
+    let verifyDigitsAsString expected =
+        TaskSeq.map char
+        >> TaskSeq.map ((+) '@')
+        >> TaskSeq.toArrayAsync
+        >> Task.map (String >> should equal expected)
+
     /// Delays (no spin-wait!) between 20 and 70ms, assuming a 15.6ms resolution clock
     let longDelay () = task { do! Task.Delay(Random().Next(20, 70)) }