Add MonitoringStream.DidFlush event

src/Nerdbank.Streams.Tests/MonitoringStreamTests.cs

@@ -392,7 +392,10 @@ public void Flush()
         var mockedUnderlyingStream = new Mock<Stream>(MockBehavior.Strict);
         mockedUnderlyingStream.Setup(s => s.Flush());
         var monitoringStream = new MonitoringStream(mockedUnderlyingStream.Object);
+        bool didFlushRaised = false;
+        monitoringStream.DidFlush += (s, e) => didFlushRaised = true;
         monitoringStream.Flush();
+        Assert.True(didFlushRaised);
         mockedUnderlyingStream.VerifyAll();
     }
 
@@ -402,7 +405,10 @@ public async Task FlushAsync()
         var mockedUnderlyingStream = new Mock<Stream>(MockBehavior.Strict);
         mockedUnderlyingStream.Setup(s => s.FlushAsync(It.IsAny<CancellationToken>())).Returns(Task.CompletedTask);
         var monitoringStream = new MonitoringStream(mockedUnderlyingStream.Object);
+        bool didFlushRaised = false;
+        monitoringStream.DidFlush += (s, e) => didFlushRaised = true;
         await monitoringStream.FlushAsync();
+        Assert.True(didFlushRaised);
         mockedUnderlyingStream.VerifyAll();
     }
 

src/Nerdbank.Streams.Tests/SubstreamTests.cs

@@ -293,7 +293,7 @@ public async Task Flush_RepeatedlyDoesNotWriteMore(bool async)
     [PairwiseData]
     public async Task Dispose_FlushesFinalBytes(bool async)
     {
-        var monitoredStream = new InstrumentedStream(this.underlyingStream);
+        var monitoredStream = new MonitoringStream(this.underlyingStream);
         int lastOperation = 0;
         monitoredStream.DidWrite += (s, e) => lastOperation = 1;
         monitoredStream.DidWriteMemory += (s, e) => lastOperation = 1;
@@ -312,7 +312,7 @@ public async Task Dispose_FlushesFinalBytes(bool async)
     [PairwiseData]
     public async Task Flush_FlushesUnderlyingStream(bool async)
     {
-        var monitoredStream = new InstrumentedStream(this.underlyingStream);
+        var monitoredStream = new MonitoringStream(this.underlyingStream);
         int flushed = 0;
         monitoredStream.DidFlush += (s, e) => flushed++;
 
@@ -382,26 +382,4 @@ private async Task DisposeSyncOrAsync(Substream stream, bool async)
             stream.Dispose();
         }
     }
-
-    private class InstrumentedStream : MonitoringStream
-    {
-        public InstrumentedStream(Stream inner)
-            : base(inner)
-        {
-        }
-
-        public event EventHandler? DidFlush;
-
-        public override void Flush()
-        {
-            base.Flush();
-            this.DidFlush?.Invoke(this, EventArgs.Empty);
-        }
-
-        public override async Task FlushAsync(CancellationToken cancellationToken)
-        {
-            await base.FlushAsync(cancellationToken);
-            this.DidFlush?.Invoke(this, EventArgs.Empty);
-        }
-    }
 }

src/Nerdbank.Streams/MonitoringStream.cs

@@ -162,6 +162,11 @@ public MonitoringStream(Stream inner)
         /// </summary>
         public event EventHandler<byte>? DidWriteByte;
 
+        /// <summary>
+        /// Occurs after <see cref="Flush"/> or <see cref="FlushAsync(CancellationToken)"/> is invoked.
+        /// </summary>
+        public event EventHandler? DidFlush;
+
         /// <summary>
         /// Occurs when <see cref="Stream.Dispose()"/> is invoked.
         /// </summary>
@@ -204,10 +209,18 @@ public override int WriteTimeout
         public override bool CanTimeout => this.inner.CanTimeout;
 
         /// <inheritdoc/>
-        public override void Flush() => this.inner.Flush();
+        public override void Flush()
+        {
+            this.inner.Flush();
+            this.DidFlush?.Invoke(this, EventArgs.Empty);
+        }
 
         /// <inheritdoc/>
-        public override Task FlushAsync(CancellationToken cancellationToken) => this.inner.FlushAsync(cancellationToken);
+        public override async Task FlushAsync(CancellationToken cancellationToken)
+        {
+            await this.inner.FlushAsync(cancellationToken).ConfigureAwait(false);
+            this.DidFlush?.Invoke(this, EventArgs.Empty);
+        }
 
         /// <inheritdoc/>
         public override int Read(byte[] buffer, int offset, int count)