Remove flaky cancellation tests and warn about FakeScheduler

It's just not right yet.
googleapis · Nov 25, 2016 · aa237eb · aa237eb
1 parent b3dad61
commit aa237eb
Show file tree

Hide file tree

Showing 3 changed files with 12 additions and 56 deletions.
diff --git a/test/Google.Api.Gax.Tests/FakeSchedulerTest.cs b/test/Google.Api.Gax.Tests/FakeSchedulerTest.cs
@@ -15,26 +15,15 @@ namespace Google.Api.Gax.Tests
 {
     public class FakeSchedulerTest
     {
+        // Note: no tests for cancellation at the moment as they're fiendishly difficult to write in a robust way.
+        // We need to revisit FakeScheduler yet again...
+
         [Fact]
         public async Task SimpleDelay()
         {
             var scheduler = new FakeScheduler();
             await scheduler.RunAsync(() => scheduler.Delay(TimeSpan.FromTicks(1000)));
             Assert.Equal(1000, scheduler.Clock.GetCurrentDateTimeUtc().Ticks);
         }
-
-        [Fact]
-        public async Task Cancellation()
-        {
-            var scheduler = new FakeScheduler();
-            await scheduler.RunAsync(async () =>
-            {
-                var cts = new CancellationTokenSource();
-                scheduler.ScheduleCancellation(TimeSpan.FromTicks(500), cts);
-                var task = scheduler.Delay(TimeSpan.FromTicks(1000), cts.Token);
-                await Assert.ThrowsAsync<TaskCanceledException>(() => scheduler.Delay(TimeSpan.FromTicks(1000), cts.Token));
-            });
-            Assert.Equal(500, scheduler.Clock.GetCurrentDateTimeUtc().Ticks);
-        }
     }
 }
diff --git a/test/Google.Api.Gax.Tests/PollingTest.cs b/test/Google.Api.Gax.Tests/PollingTest.cs
@@ -15,6 +15,9 @@ namespace Google.Api.Gax.Tests
 {
     public class PollingTest
     {
+        // Note: no tests for cancellation at the moment as they're fiendishly difficult to write in a robust way.
+        // We need to revisit FakeScheduler yet again...
+
         [Fact]
         public void PollToCompletion_Success()
         {
@@ -41,20 +44,6 @@ public void PollToCompletion_Timeout()
             });
         }
 
-        [Fact]
-        public void PollToCompletion_Cancellation()
-        {
-            var cts = new CancellationTokenSource();
-            var pollSource = new PollSource(TimeSpan.FromSeconds(4), 5);
-            var pollSettings = new PollSettings(Expiration.FromTimeout(TimeSpan.FromSeconds(5)), TimeSpan.FromSeconds(2));
-            pollSource.Scheduler.ScheduleCancellation(TimeSpan.FromSeconds(3), cts);
-            pollSource.Scheduler.Run(() =>
-            {
-                Assert.Throws<TaskCanceledException>(() => pollSource.PollRepeatedly(pollSettings, cts.Token));
-                Assert.Equal(TimeSpan.FromSeconds(3), pollSource.RunningTime);
-            });
-        }
-
         [Fact]
         public async Task PollToCompletionAsync_Success()
         {
@@ -81,20 +70,6 @@ await pollSource.Scheduler.RunAsync(async () =>
             });
         }
 
-        [Fact]
-        public async Task PollToCompletionAsync_Cancellation()
-        {
-            var cts = new CancellationTokenSource();
-            var pollSource = new PollSource(TimeSpan.FromSeconds(4), 5);
-            var pollSettings = new PollSettings(Expiration.FromTimeout(TimeSpan.FromSeconds(5)), TimeSpan.FromSeconds(2));
-            pollSource.Scheduler.ScheduleCancellation(TimeSpan.FromSeconds(3), cts);
-            await pollSource.Scheduler.RunAsync(async () =>
-            {
-                await Assert.ThrowsAsync<TaskCanceledException>(() => pollSource.PollRepeatedlyAsync(pollSettings, cts.Token));
-                Assert.Equal(TimeSpan.FromSeconds(3), pollSource.RunningTime);
-            });
-        }
-
         private class PollSource
         {
             public FakeScheduler Scheduler { get; } = new FakeScheduler();

diff --git a/testing/Google.Api.Gax.Testing/FakeScheduler.cs b/testing/Google.Api.Gax.Testing/FakeScheduler.cs
@@ -13,9 +13,14 @@
 namespace Google.Api.Gax.Testing
 {
     /// <summary>
-    /// Fake implementation of <see cref="IScheduler" />, designed to work with
+    /// Experimental - please read reamarks. Fake implementation of <see cref="IScheduler" />, designed to work with
     /// <see cref="FakeClock"/>.
     /// </summary>
+    /// <remarks>
+    /// This class is currently hard to use robustly, and cancellation in particular is hard.
+    /// The API and behavior may change in future versions without a major version bump - in other words,
+    /// this is not considered part of the stable API of the package.
+    /// </remarks>
     public sealed class FakeScheduler : IScheduler
     {
         /// <summary>
@@ -57,19 +62,6 @@ public FakeScheduler() : this(new FakeClock(0L))
         public Task Delay(TimeSpan delay, CancellationToken cancellationToken = default(CancellationToken)) =>
             AddTimer(Clock.GetCurrentDateTimeUtc() + delay, cancellationToken);
 
-        /// <summary>
-        /// Schedules tokens from the given source to be cancelled in the future. Use of this method
-        /// ensures that any tasks depending on tokens from this source will be cancelled before the clock advances further.
-        /// </summary>
-        /// <param name="delay">The delay in cancelling (i.e. when we should cancel)</param>
-        /// <param name="cts">The cancellation token source to cancel.</param>
-        public void ScheduleCancellation(TimeSpan delay, CancellationTokenSource cts)
-        {
-            // We need to execute synchronously so that any tasks will really be cancelled before
-            // the clock advances again.
-            Delay(delay).ContinueWith(_ => cts.Cancel(), TaskContinuationOptions.ExecuteSynchronously);
-        }
-
         /// <summary>
         /// Specialization of <see cref="Run{T}(Func{T})"/> for tasks, to prevent a common usage error.
         /// </summary>