Prevent Advance/SetUtcNow moving time backwards

dotnet · Jun 6, 2023 · 145515a · 145515a
1 parent 91916ff
commit 145515a
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Showing 2 changed files with 16 additions and 1 deletion.
diff --git a/src/Libraries/Microsoft.Extensions.TimeProvider.Testing/FakeTimeProvider.cs b/src/Libraries/Microsoft.Extensions.TimeProvider.Testing/FakeTimeProvider.cs
@@ -7,6 +7,7 @@
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Threading;
+using Microsoft.Shared.Diagnostics;
 
 namespace Microsoft.Extensions.Time.Testing;
 
@@ -68,7 +69,12 @@ public override DateTimeOffset GetUtcNow()
     /// <param name="value">The date and time in the UTC timezone.</param>
     public void SetUtcNow(DateTimeOffset value)
     {
-        while (_now <= value && TryGetWaiterToWake(value) is FakeTimeProviderTimer.Waiter waiter)
+        if (value < _now)
+        {
+            Throw.ArgumentOutOfRangeException(nameof(value), $"Cannot go back in time. Current time is {GetUtcNow()}.");
+        }
+
+        while (value >= _now && TryGetWaiterToWake(value) is FakeTimeProviderTimer.Waiter waiter)
         {
             _now = waiter.WakeupTime;
             waiter.TriggerAndSchedule(false);

diff --git a/test/Libraries/Microsoft.Extensions.TimeProvider.Testing.Tests/FakeTimeProviderTests.cs b/test/Libraries/Microsoft.Extensions.TimeProvider.Testing.Tests/FakeTimeProviderTests.cs
@@ -136,6 +136,15 @@ public void AdvanceGoesForward()
         Assert.Equal(1234, elapsedTime.TotalMilliseconds);
     }
 
+    [Fact]
+    public void TimeCannotGoBackwards()
+    {
+        var timeProvider = new FakeTimeProvider();
+
+        Assert.Throws<ArgumentOutOfRangeException>(() => timeProvider.Advance(TimeSpan.FromTicks(-1)));
+        Assert.Throws<ArgumentOutOfRangeException>(() => timeProvider.SetUtcNow(timeProvider.Epoch - TimeSpan.FromTicks(1)));
+    }
+
     [Fact]
     public void ToStr()
     {