Support exponential backoff

src/TestFramework/TestFramework/Attributes/TestMethod/DelayBackoffType.cs

@@ -0,0 +1,22 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.VisualStudio.TestTools.UnitTesting;
+
+/// <summary>
+/// Specifies a backoff type for the delay between retries.
+/// </summary>
+public enum DelayBackoffType
+{
+    /// <summary>
+    /// Specifies a constant backoff type. Meaning the delay between retries is constant.
+    /// </summary>
+    Constant,
+
+    /// <summary>
+    /// Specifies an exponential backoff type.
+    /// The delay is calculated as the base delay * 2^(n-1) where n is the retry attempt.
+    /// For example, if the base delay is 1000ms, the delays will be 1000ms, 2000ms, 4000ms, 8000ms, etc.
+    /// </summary>
+    Exponential,
+}

src/TestFramework/TestFramework/Attributes/TestMethod/RetryAttribute.cs

@@ -3,17 +3,6 @@
 
 namespace Microsoft.VisualStudio.TestTools.UnitTesting;
 
-public sealed class RetryResult
-{
-    private readonly List<TestResult[]> _testResults = new();
-
-    public void AddResult(TestResult[] testResults)
-        => _testResults.Add(testResults);
-
-    internal TestResult[]? TryGetLast()
-        => _testResults.Count > 0 ? _testResults[_testResults.Count - 1] : null;
-}
-
 /// <summary>
 /// This attribute is used to set a retry count on a test method in case of failure.
 /// </summary>
@@ -47,6 +36,20 @@ public RetryAttribute(int maxRetryAttempts)
     /// </summary>
     public int MillisecondsDelayBetweenRetries { get; set; }
 
+    public DelayBackoffType BackoffType
+    {
+        get => field;
+        set
+        {
+            if (value is < DelayBackoffType.Constant or > DelayBackoffType.Exponential)
+            {
+                throw new ArgumentOutOfRangeException(nameof(value));
+            }
+
+            field = value;
+        }
+    }
+
     /// <summary>
     /// Retries the test method <see cref="MaxRetryAttempts"/> times in case of failure.
     /// Note that a first run of the method was already executed and failed before this method is called.
@@ -61,10 +64,15 @@ public RetryAttribute(int maxRetryAttempts)
     protected internal virtual async Task<RetryResult> ExecuteAsync(RetryContext retryContext)
     {
         var result = new RetryResult();
+        int currentDelay = MillisecondsDelayBetweenRetries;
         for (int i = 0; i < MaxRetryAttempts; i++)
         {
             // The caller already executed the test once. So we need to do the delay here.
-            await Task.Delay(MillisecondsDelayBetweenRetries);
+            await Task.Delay(currentDelay);
+            if (BackoffType == DelayBackoffType.Exponential)
+            {
+                currentDelay *= 2;
+            }
 
             TestResult[] testResults = await retryContext.ExecuteTaskGetter();
             result.AddResult(testResults);

src/TestFramework/TestFramework/Attributes/TestMethod/RetryResult.cs

@@ -0,0 +1,15 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.VisualStudio.TestTools.UnitTesting;
+
+public sealed class RetryResult
+{
+    private readonly List<TestResult[]> _testResults = new();
+
+    public void AddResult(TestResult[] testResults)
+        => _testResults.Add(testResults);
+
+    internal TestResult[]? TryGetLast()
+        => _testResults.Count > 0 ? _testResults[_testResults.Count - 1] : null;
+}

src/TestFramework/TestFramework/PublicAPI/PublicAPI.Unshipped.txt

@@ -190,6 +190,9 @@ Microsoft.VisualStudio.TestTools.UnitTesting.Assert.AssertThrowsExactlyInterpola
 Microsoft.VisualStudio.TestTools.UnitTesting.Assert.AssertThrowsExactlyInterpolatedStringHandler<TException>.AssertThrowsExactlyInterpolatedStringHandler(int literalLength, int formattedCount, System.Action! action, out bool shouldAppend) -> void
 Microsoft.VisualStudio.TestTools.UnitTesting.DataRowAttribute.IgnoreMessage.get -> string?
 Microsoft.VisualStudio.TestTools.UnitTesting.DataRowAttribute.IgnoreMessage.set -> void
+Microsoft.VisualStudio.TestTools.UnitTesting.DelayBackoffType
+Microsoft.VisualStudio.TestTools.UnitTesting.DelayBackoffType.Constant = 0 -> Microsoft.VisualStudio.TestTools.UnitTesting.DelayBackoffType
+Microsoft.VisualStudio.TestTools.UnitTesting.DelayBackoffType.Exponential = 1 -> Microsoft.VisualStudio.TestTools.UnitTesting.DelayBackoffType
 Microsoft.VisualStudio.TestTools.UnitTesting.DynamicDataAttribute.DynamicDataAttribute(string! dynamicDataSourceName) -> void
 Microsoft.VisualStudio.TestTools.UnitTesting.DynamicDataAttribute.DynamicDataAttribute(string! dynamicDataSourceName, Microsoft.VisualStudio.TestTools.UnitTesting.DynamicDataSourceType dynamicDataSourceType) -> void
 Microsoft.VisualStudio.TestTools.UnitTesting.DynamicDataAttribute.DynamicDataAttribute(string! dynamicDataSourceName, System.Type! dynamicDataDeclaringType) -> void
@@ -203,6 +206,8 @@ Microsoft.VisualStudio.TestTools.UnitTesting.ITestDataSourceIgnoreCapability
 Microsoft.VisualStudio.TestTools.UnitTesting.ITestDataSourceIgnoreCapability.IgnoreMessage.get -> string?
 Microsoft.VisualStudio.TestTools.UnitTesting.ITestDataSourceIgnoreCapability.IgnoreMessage.set -> void
 Microsoft.VisualStudio.TestTools.UnitTesting.RetryAttribute
+Microsoft.VisualStudio.TestTools.UnitTesting.RetryAttribute.BackoffType.get -> Microsoft.VisualStudio.TestTools.UnitTesting.DelayBackoffType
+Microsoft.VisualStudio.TestTools.UnitTesting.RetryAttribute.BackoffType.set -> void
 Microsoft.VisualStudio.TestTools.UnitTesting.RetryAttribute.MaxRetryAttempts.get -> int
 Microsoft.VisualStudio.TestTools.UnitTesting.RetryAttribute.MillisecondsDelayBetweenRetries.get -> int
 Microsoft.VisualStudio.TestTools.UnitTesting.RetryAttribute.MillisecondsDelayBetweenRetries.set -> void