Add report file retry helper tests

test/UnitTests/Microsoft.Testing.Extensions.UnitTests/ReportFileWriterHelperTests.cs

@@ -0,0 +1,205 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.Testing.Platform.Helpers;
+
+namespace Microsoft.Testing.Extensions.UnitTests;
+
+[TestClass]
+public sealed class ReportFileWriterHelperTests
+{
+    private static readonly DateTimeOffset StartTime = new(2026, 1, 1, 0, 0, 0, TimeSpan.Zero);
+
+    [TestMethod]
+    public async Task RetryWhenIOExceptionAsync_ImmediateSuccess_ReturnsResultWithoutRetrying()
+    {
+        var clock = new SequenceClock(StartTime);
+        int invocationCount = 0;
+
+        int result = await ReportFileWriterHelper.RetryWhenIOExceptionAsync(clock, () =>
+        {
+            invocationCount++;
+            return Task.FromResult(42);
+        });
+
+        Assert.AreEqual(42, result);
+        Assert.AreEqual(1, invocationCount);
+        Assert.AreEqual(1, clock.ReadCount);
+        Assert.AreEqual(0, clock.RemainingCount);
+    }
+
+    [TestMethod]
+    public async Task RetryWhenIOExceptionAsync_TransientIOException_RetriesUntilSuccess()
+    {
+        var clock = new SequenceClock(
+            StartTime,
+            StartTime + ReportFileWriterHelper.FileWriteRetryTimeout - TimeSpan.FromTicks(1));
+        int invocationCount = 0;
+
+        int result = await ReportFileWriterHelper.RetryWhenIOExceptionAsync(clock, () =>
+        {
+            invocationCount++;
+            return invocationCount == 1
+                ? Task.FromException<int>(new IOException("The report file is temporarily locked."))
+                : Task.FromResult(42);
+        });
+
+        Assert.AreEqual(42, result);
+        Assert.AreEqual(2, invocationCount);
+        Assert.AreEqual(2, clock.ReadCount);
+        Assert.AreEqual(0, clock.RemainingCount);
+    }
+
+    [TestMethod]
+    public async Task RetryWhenIOExceptionAsync_IOExceptionAtTimeoutBoundary_Retries()
+    {
+        var clock = new SequenceClock(
+            StartTime,
+            StartTime + ReportFileWriterHelper.FileWriteRetryTimeout,
+            StartTime + ReportFileWriterHelper.FileWriteRetryTimeout);
+        int invocationCount = 0;
+
+        int result = await ReportFileWriterHelper.RetryWhenIOExceptionAsync(clock, () =>
+        {
+            invocationCount++;
+            return invocationCount <= 2
+                ? Task.FromException<int>(new IOException("The report file is temporarily locked."))
+                : Task.FromResult(42);
+        });
+
+        Assert.AreEqual(42, result);
+        Assert.AreEqual(3, invocationCount);
+        Assert.AreEqual(3, clock.ReadCount);
+        Assert.AreEqual(0, clock.RemainingCount);
+    }
+
+    [TestMethod]
+    public async Task RetryWhenIOExceptionAsync_TimeoutExceeded_RethrowsNextIOException()
+    {
+        var clock = new SequenceClock(
+            StartTime,
+            StartTime + ReportFileWriterHelper.FileWriteRetryTimeout + TimeSpan.FromTicks(1));
+        var firstException = new IOException("The report file is temporarily locked.");
+        var expectedException = new IOException("The report file remains locked.");
+        int invocationCount = 0;
+
+        IOException actualException = await Assert.ThrowsExactlyAsync<IOException>(
+            () => ReportFileWriterHelper.RetryWhenIOExceptionAsync<int>(clock, () =>
+            {
+                invocationCount++;
+                return Task.FromException<int>(invocationCount == 1 ? firstException : expectedException);
+            }));
+
+        Assert.AreSame(expectedException, actualException);
+        Assert.AreEqual(2, invocationCount);
+        Assert.AreEqual(2, clock.ReadCount);
+        Assert.AreEqual(0, clock.RemainingCount);
+    }
+
+    [TestMethod]
+    public async Task RetryWhenIOExceptionAsync_TimeoutExceeded_ReturnsResultWhenNextInvocationSucceeds()
+    {
+        var clock = new SequenceClock(
+            StartTime,
+            StartTime + ReportFileWriterHelper.FileWriteRetryTimeout + TimeSpan.FromTicks(1));
+        int invocationCount = 0;
+
+        int result = await ReportFileWriterHelper.RetryWhenIOExceptionAsync(clock, () =>
+        {
+            invocationCount++;
+            return invocationCount == 1
+                ? Task.FromException<int>(new IOException("The report file is temporarily locked."))
+                : Task.FromResult(42);
+        });
+
+        Assert.AreEqual(42, result);
+        Assert.AreEqual(2, invocationCount);
+        Assert.AreEqual(2, clock.ReadCount);
+        Assert.AreEqual(0, clock.RemainingCount);
+    }
+
+    [TestMethod]
+    public async Task RetryWhenIOExceptionAsync_NonIOExceptionAfterRetry_PropagatesWithoutFurtherRetrying()
+    {
+        var clock = new SequenceClock(
+            StartTime,
+            StartTime + ReportFileWriterHelper.FileWriteRetryTimeout - TimeSpan.FromTicks(1));
+        var expectedException = new InvalidOperationException("Report generation failed.");
+        int invocationCount = 0;
+
+        InvalidOperationException actualException = await Assert.ThrowsExactlyAsync<InvalidOperationException>(
+            () => ReportFileWriterHelper.RetryWhenIOExceptionAsync<int>(clock, () =>
+            {
+                invocationCount++;
+                return Task.FromException<int>(
+                    invocationCount == 1
+                        ? new IOException("The report file is temporarily locked.")
+                        : expectedException);
+            }));
+
+        Assert.AreSame(expectedException, actualException);
+        Assert.AreEqual(2, invocationCount);
+        Assert.AreEqual(2, clock.ReadCount);
+        Assert.AreEqual(0, clock.RemainingCount);
+    }
+
+    [TestMethod]
+    public async Task RetryWhenIOExceptionAsync_NonIOException_PropagatesWithoutRetrying()
+    {
+        var clock = new SequenceClock(StartTime);
+        var expectedException = new InvalidOperationException("Report generation failed.");
+        int invocationCount = 0;
+
+        InvalidOperationException actualException = await Assert.ThrowsExactlyAsync<InvalidOperationException>(
+            () => ReportFileWriterHelper.RetryWhenIOExceptionAsync<int>(clock, () =>
+            {
+                invocationCount++;
+                return Task.FromException<int>(expectedException);
+            }));
+
+        Assert.AreSame(expectedException, actualException);
+        Assert.AreEqual(1, invocationCount);
+        Assert.AreEqual(1, clock.ReadCount);
+        Assert.AreEqual(0, clock.RemainingCount);
+    }
+
+    [TestMethod]
+    public async Task RetryWhenIOExceptionAsync_CanceledOperation_PropagatesWithoutRetrying()
+    {
+        var clock = new SequenceClock(StartTime);
+        var cancellationToken = new CancellationToken(canceled: true);
+        int invocationCount = 0;
+
+        TaskCanceledException exception = await Assert.ThrowsExactlyAsync<TaskCanceledException>(
+            () => ReportFileWriterHelper.RetryWhenIOExceptionAsync<int>(clock, () =>
+            {
+                invocationCount++;
+                return Task.FromCanceled<int>(cancellationToken);
+            }));
+
+        Assert.AreEqual(cancellationToken, exception.CancellationToken);
+        Assert.AreEqual(1, invocationCount);
+        Assert.AreEqual(1, clock.ReadCount);
+        Assert.AreEqual(0, clock.RemainingCount);
+    }
+
+    private sealed class SequenceClock(params DateTimeOffset[] timestamps) : IClock
+    {
+        private readonly Queue<DateTimeOffset> _timestamps = new(timestamps);
+
+        public int ReadCount { get; private set; }
+
+        public int RemainingCount => _timestamps.Count;
+
+        public DateTimeOffset UtcNow
+        {
+            get
+            {
+                ReadCount++;
+                return _timestamps.Count > 0
+                    ? _timestamps.Dequeue()
+                    : throw new InvalidOperationException("The retry helper read the clock more times than expected.");
+            }
+        }
+    }
+}