diff --git a/src/FSharp.Control.TaskSeq.Test/FSharp.Control.TaskSeq.Test.fsproj b/src/FSharp.Control.TaskSeq.Test/FSharp.Control.TaskSeq.Test.fsproj
index ff7ae5e..d625d93 100644
--- a/src/FSharp.Control.TaskSeq.Test/FSharp.Control.TaskSeq.Test.fsproj
+++ b/src/FSharp.Control.TaskSeq.Test/FSharp.Control.TaskSeq.Test.fsproj
@@ -24,6 +24,7 @@
     <Compile Include="TaskSeq.FindIndex.Tests.fs" />
     <Compile Include="TaskSeq.Find.Tests.fs" />
     <Compile Include="TaskSeq.Fold.Tests.fs" />
+    <Compile Include="TaskSeq.Forall.Tests.fs" />
     <Compile Include="TaskSeq.Head.Tests.fs" />
     <Compile Include="TaskSeq.Indexed.Tests.fs" />
     <Compile Include="TaskSeq.Init.Tests.fs" />
diff --git a/src/FSharp.Control.TaskSeq.Test/TaskSeq.Forall.Tests.fs b/src/FSharp.Control.TaskSeq.Test/TaskSeq.Forall.Tests.fs
new file mode 100644
index 0000000..04a652f
--- /dev/null
+++ b/src/FSharp.Control.TaskSeq.Test/TaskSeq.Forall.Tests.fs
@@ -0,0 +1,228 @@
+module TaskSeq.Tests.Exists
+
+open Xunit
+open FsUnit.Xunit
+
+open FSharp.Control
+
+//
+// TaskSeq.exists
+// TaskSeq.existsAsyncc
+//
+
+module EmptySeq =
+    [<Fact>]
+    let ``Null source is invalid`` () =
+        assertNullArg
+        <| fun () -> TaskSeq.exists (fun _ -> false) null
+
+        assertNullArg
+        <| fun () -> TaskSeq.existsAsync (fun _ -> Task.fromResult false) null
+
+    [<Theory; ClassData(typeof<TestEmptyVariants>)>]
+    let ``TaskSeq-exists returns false`` variant =
+        Gen.getEmptyVariant variant
+        |> TaskSeq.exists ((=) 12)
+        |> Task.map (should be False)
+
+    [<Theory; ClassData(typeof<TestEmptyVariants>)>]
+    let ``TaskSeq-existsAsync returns false`` variant =
+        Gen.getEmptyVariant variant
+        |> TaskSeq.existsAsync (fun x -> task { return x = 12 })
+        |> Task.map (should be False)
+
+module Immutable =
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-exists sad path returns false`` variant =
+        Gen.getSeqImmutable variant
+        |> TaskSeq.exists ((=) 0)
+        |> Task.map (should be False)
+
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-existsAsync sad path return false`` variant =
+        Gen.getSeqImmutable variant
+        |> TaskSeq.existsAsync (fun x -> task { return x = 0 })
+        |> Task.map (should be False)
+
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-exists happy path middle of seq`` variant =
+        Gen.getSeqImmutable variant
+        |> TaskSeq.exists (fun x -> x < 6 && x > 4)
+        |> Task.map (should be True)
+
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-existsAsync happy path middle of seq`` variant =
+        Gen.getSeqImmutable variant
+        |> TaskSeq.existsAsync (fun x -> task { return x < 6 && x > 4 })
+        |> Task.map (should be True)
+
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-exists happy path first item of seq`` variant =
+        Gen.getSeqImmutable variant
+        |> TaskSeq.exists ((=) 1)
+        |> Task.map (should be True)
+
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-existsAsync happy path first item of seq`` variant =
+        Gen.getSeqImmutable variant
+        |> TaskSeq.existsAsync (fun x -> task { return x = 1 })
+        |> Task.map (should be True)
+
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-exists happy path last item of seq`` variant =
+        Gen.getSeqImmutable variant
+        |> TaskSeq.exists ((=) 10)
+        |> Task.map (should be True)
+
+    [<Theory; ClassData(typeof<TestImmTaskSeq>)>]
+    let ``TaskSeq-existsAsync happy path last item of seq`` variant =
+        Gen.getSeqImmutable variant
+        |> TaskSeq.existsAsync (fun x -> task { return x = 10 })
+        |> Task.map (should be True)
+
+module SideEffects =
+    [<Theory; ClassData(typeof<TestSideEffectTaskSeq>)>]
+    let ``TaskSeq-exists KeyNotFoundException only sometimes for mutated state`` variant = task {
+        let ts = Gen.getSeqWithSideEffect variant
+        let finder = (=) 11
+
+        // first: false
+        let! found = TaskSeq.exists finder ts
+        found |> should be False
+
+        // find again: found now, because of side effects
+        let! found = TaskSeq.exists finder ts
+        found |> should be True
+
+        // find once more: false
+        let! found = TaskSeq.exists finder ts
+        found |> should be False
+    }
+
+    [<Theory; ClassData(typeof<TestSideEffectTaskSeq>)>]
+    let ``TaskSeq-existsAsync KeyNotFoundException only sometimes for mutated state`` variant = task {
+        let ts = Gen.getSeqWithSideEffect variant
+        let finder x = task { return x = 11 }
+
+        // first: false
+        let! found = TaskSeq.existsAsync finder ts
+        found |> should be False
+
+        // find again: found now, because of side effects
+        let! found = TaskSeq.existsAsync finder ts
+        found |> should be True
+
+        // find once more: false
+        let! found = TaskSeq.existsAsync finder ts
+        found |> should be False
+    }
+
+    [<Fact>]
+    let ``TaskSeq-exists _specialcase_ prove we don't read past the found item`` () = task {
+        let mutable i = 0
+
+        let ts = taskSeq {
+            for _ in 0..9 do
+                i <- i + 1
+                yield i
+        }
+
+        let! found = ts |> TaskSeq.exists ((=) 3)
+        found |> should be True
+        i |> should equal 3 // only partial evaluation!
+
+        // find next item. We do get a new iterator, but mutable state is now starting at '3', so first item now returned is '4'.
+        let! found = ts |> TaskSeq.exists ((=) 4)
+        found |> should be True
+        i |> should equal 4 // only partial evaluation!
+    }
+
+    [<Fact>]
+    let ``TaskSeq-existsAsync _specialcase_ prove we don't read past the found item`` () = task {
+        let mutable i = 0
+
+        let ts = taskSeq {
+            for _ in 0..9 do
+                i <- i + 1
+                yield i
+        }
+
+        let! found = ts |> TaskSeq.existsAsync (fun x -> task { return x = 3 })
+        found |> should be True
+        i |> should equal 3 // only partial evaluation!
+
+        // find next item. We do get a new iterator, but mutable state is now starting at '3', so first item now returned is '4'.
+        let! found = ts |> TaskSeq.existsAsync (fun x -> task { return x = 4 })
+        found |> should be True
+        i |> should equal 4
+    }
+
+    [<Fact>]
+    let ``TaskSeq-exists _specialcase_ prove we don't read past the found item v2`` () = task {
+        let mutable i = 0
+
+        let ts = taskSeq {
+            yield 42
+            i <- i + 1
+            i <- i + 1
+        }
+
+        let! found = ts |> TaskSeq.exists ((=) 42)
+        found |> should be True
+        i |> should equal 0 // because no MoveNext after found item, the last statements are not executed
+    }
+
+    [<Fact>]
+    let ``TaskSeq-existsAsync _specialcase_ prove we don't read past the found item v2`` () = task {
+        let mutable i = 0
+
+        let ts = taskSeq {
+            yield 42
+            i <- i + 1
+            i <- i + 1
+        }
+
+        let! found = ts |> TaskSeq.existsAsync (fun x -> task { return x = 42 })
+        found |> should be True
+        i |> should equal 0 // because no MoveNext after found item, the last statements are not executed
+    }
+
+    [<Fact>]
+    let ``TaskSeq-exists _specialcase_ prove statement after yield is not evaluated`` () = task {
+        let mutable i = 0
+
+        let ts = taskSeq {
+            for _ in 0..9 do
+                yield i
+                i <- i + 1
+        }
+
+        let! found = ts |> TaskSeq.exists ((=) 0)
+        found |> should be True
+        i |> should equal 0 // notice that it should be one higher if the statement after 'yield' is evaluated
+
+        // find some next item. We do get a new iterator, but mutable state is now starting at '1'
+        let! found = ts |> TaskSeq.exists ((=) 4)
+        found |> should be True
+        i |> should equal 4 // only partial evaluation!
+    }
+
+    [<Fact>]
+    let ``TaskSeq-existsAsync _specialcase_ prove statement after yield is not evaluated`` () = task {
+        let mutable i = 0
+
+        let ts = taskSeq {
+            for _ in 0..9 do
+                yield i
+                i <- i + 1
+        }
+
+        let! found = ts |> TaskSeq.existsAsync (fun x -> task { return x = 0 })
+        found |> should be True
+        i |> should equal 0 // notice that it should be one higher if the statement after 'yield' is evaluated
+
+        // find some next item. We do get a new iterator, but mutable state is now starting at '1'
+        let! found = ts |> TaskSeq.existsAsync (fun x -> task { return x = 4 })
+        found |> should be True
+        i |> should equal 4 // only partial evaluation!
+    }