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Fix race condition in BackgroundServiceExceptionTests #125570

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Fix race condition in BackgroundServiceExceptionTests #125570

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b4d5f00
Fix race condition in BackgroundServiceExceptionTests
lewing Mar 15, 2026
a504b8d
Fix comment: signal fires before throw, not after
lewing Mar 15, 2026
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39 changes: 32 additions & 7 deletions ...libraries/Microsoft.Extensions.Hosting/tests/UnitTests/BackgroundServiceExceptionTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -78,8 +78,11 @@ public async Task BackgroundService_AsynchronousException_StopAsync_ThrowsExcept
using var host = builder.Build();
await host.StartAsync();

// Wait for the background service to fail
await Task.Delay(TimeSpan.FromMilliseconds(200));
// Wait for the host to react to the background service failure
var lifetime = host.Services.GetRequiredService<IHostApplicationLifetime>();
var stoppingTcs = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
lifetime.ApplicationStopping.Register(() => stoppingTcs.TrySetResult());
await stoppingTcs.Task.WaitAsync(TimeSpan.FromSeconds(10));

await Assert.ThrowsAsync<InvalidOperationException>(async () =>
{
Expand Down Expand Up @@ -107,8 +110,11 @@ public async Task BackgroundService_AsynchronousException_StopTwiceAsync_ThrowsE
using var host = builder.Build();
await host.StartAsync();

// Wait for the background service to fail
await Task.Delay(TimeSpan.FromMilliseconds(200));
// Wait for the host to react to the background service failure
var lifetime = host.Services.GetRequiredService<IHostApplicationLifetime>();
var stoppingTcs = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
lifetime.ApplicationStopping.Register(() => stoppingTcs.TrySetResult());
await stoppingTcs.Task.WaitAsync(TimeSpan.FromSeconds(10));

await Assert.ThrowsAsync<InvalidOperationException>(async () =>
{
Expand Down Expand Up @@ -208,6 +214,7 @@ public async Task BackgroundService_IgnoreException_DoesNotThrow()
[Fact]
public async Task BackgroundService_IgnoreException_StopAsync_DoesNotThrow()
{
var signal = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
var builder = new HostBuilder()
.ConfigureServices(services =>
{
Expand All @@ -216,14 +223,15 @@ public async Task BackgroundService_IgnoreException_StopAsync_DoesNotThrow()
options.BackgroundServiceExceptionBehavior = BackgroundServiceExceptionBehavior.Ignore;
options.ShutdownTimeout = TimeSpan.FromSeconds(1);
});
services.AddHostedService<AsynchronousFailureService>();
services.AddSingleton(signal);
services.AddHostedService<SignalingFailureService>();
});

using var host = builder.Build();
await host.StartAsync();

// Wait a bit for the background service to fail
await Task.Delay(TimeSpan.FromMilliseconds(200));
// Wait for the background service to reach its failure point
await signal.Task.WaitAsync(TimeSpan.FromSeconds(10));

await host.StopAsync();
}
Expand Down Expand Up @@ -294,6 +302,23 @@ private class StopFailureService : IHostedService
public Task StopAsync(CancellationToken cancellationToken) => throw new InvalidOperationException("Stop failure");
}

private class SignalingFailureService : BackgroundService
{
private readonly TaskCompletionSource _signal;

public SignalingFailureService(TaskCompletionSource signal)
{
_signal = signal;
}

protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
await Task.Delay(TimeSpan.FromMilliseconds(100));
_signal.TrySetResult();
throw new InvalidOperationException("Signaling asynchronous failure");
}
}

private class SuccessfulService : BackgroundService
{
private readonly IHostApplicationLifetime _lifetime;
Expand Down
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