diff --git a/Emulsion.Tests/Emulsion.Tests.fsproj b/Emulsion.Tests/Emulsion.Tests.fsproj
index 75939ad..0137ce4 100644
--- a/Emulsion.Tests/Emulsion.Tests.fsproj
+++ b/Emulsion.Tests/Emulsion.Tests.fsproj
@@ -5,7 +5,8 @@
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="Settings.fs" />
-    <Compile Include="MessageSystem.fs" />
+    <Compile Include="MessageSenderTests.fs" />
+    <Compile Include="MessageSystemTests.fs" />
     <Compile Include="Actors/Core.fs" />
     <Compile Include="Actors/SyncTaskWatcher.fs" />
     <Compile Include="Actors/Telegram.fs" />
diff --git a/Emulsion.Tests/MessageSenderTests.fs b/Emulsion.Tests/MessageSenderTests.fs
new file mode 100644
index 0000000..293d1ce
--- /dev/null
+++ b/Emulsion.Tests/MessageSenderTests.fs
@@ -0,0 +1,59 @@
+module Emulsion.Tests.MessageSenderTests
+
+open System
+open System.Threading
+
+open Xunit
+open Emulsion
+open Emulsion.MessageSender
+
+let private testContext = {
+    send = fun _ -> async { return () }
+    logError = ignore
+    cooldown = TimeSpan.Zero
+}
+
+[<Fact>]
+let ``Message sender sends the messages sequentially``() =
+    use cts = new CancellationTokenSource()
+    let messagesReceived = ResizeArray()
+    let context = {
+        testContext with
+            send = fun m -> async {
+                lock messagesReceived (fun () ->
+                    messagesReceived.Add m
+                )
+            }
+    }
+    let sender = MessageSender.startActivity(context, cts.Token)
+
+    let messagesSent = [| 1..100 |] |> Array.map (fun i ->
+        OutgoingMessage {
+            author = "author"
+            text = string i
+        }
+    )
+    messagesSent |> Array.iter(MessageSender.send sender)
+
+    SpinWait.SpinUntil((fun () -> messagesReceived.Count = messagesSent.Length), TimeSpan.FromSeconds 30.0)
+    |> Assert.True
+
+    Assert.Equal(messagesSent, messagesReceived)
+
+[<Fact>]
+let ``Message sender should be cancellable``() =
+    use cts = new CancellationTokenSource()
+    let errors = ResizeArray()
+    let context = {
+        testContext with
+            send = fun _ -> failwith "Should not be called"
+            logError = fun e -> lock errors (fun () -> errors.Add e)
+    }
+    let sender = MessageSender.startActivity(context, cts.Token)
+    cts.Cancel()
+
+    let msg = OutgoingMessage { author = "author"; text = "xx" }
+    MessageSender.send sender msg
+
+    SpinWait.SpinUntil((fun () -> errors.Count > 0), TimeSpan.FromMilliseconds 100.0) |> ignore
+    Assert.Empty errors
diff --git a/Emulsion.Tests/MessageSystem.fs b/Emulsion.Tests/MessageSystemTests.fs
similarity index 96%
rename from Emulsion.Tests/MessageSystem.fs
rename to Emulsion.Tests/MessageSystemTests.fs
index b929e51..e6c6d57 100644
--- a/Emulsion.Tests/MessageSystem.fs
+++ b/Emulsion.Tests/MessageSystemTests.fs
@@ -1,4 +1,4 @@
-module Emulsion.Tests.MessageSystem
+module Emulsion.Tests.MessageSystemTests
 
 open System
 open System.Threading
diff --git a/Emulsion/MessageSender.fs b/Emulsion/MessageSender.fs
index 6fe0970..5138b2b 100644
--- a/Emulsion/MessageSender.fs
+++ b/Emulsion/MessageSender.fs
@@ -32,4 +32,3 @@ let startActivity(ctx: MessageSenderContext, token: CancellationToken): Sender =
     MailboxProcessor.Start(receiver ctx, token)
 
 let send(activity: Sender): OutgoingMessage -> unit = activity.Post
-// TODO[F]: Tests for this module.