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Make the download cancel test deterministic #503

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Merged
KnifeLemon merged 1 commit into from
Oct 23, 2026
Merged

Make the download cancel test deterministic #503

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26 changes: 13 additions & 13 deletions tests/Filee.Core.Tests/WebDownloaderTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -220,27 +220,29 @@ public async Task Gives_up_on_a_server_that_doesnt_answer_or_stalls()
[Fact]
public async Task Cancelling_stops_the_download_and_removes_the_partial_file()
{
var started = new TaskCompletionSource();
// A first chunk past the sniffed head, so the file gets created, then nothing until the test is over.
var chunk = new byte[WebFormats.SniffLength * 4];
Png.CopyTo(chunk, 0);
_routes["/slow.png"] = async context =>
{
context.Response.ContentType = "image/png";
context.Response.ContentLength64 = 10_000;
await context.Response.OutputStream.WriteAsync(Png);
await context.Response.OutputStream.WriteAsync(chunk);
await context.Response.OutputStream.FlushAsync();
started.TrySetResult();
await Task.Delay(TimeSpan.FromSeconds(5), _stop.Token);
await Task.Delay(Timeout.Infinite, _stop.Token);
};
using var downloader = Downloader();
using var cancel = CancellationTokenSource.CreateLinkedTokenSource(TestContext.Current.CancellationToken);
var progress = new List<TransferProgress>();
// The first report comes right after the file is created and the head written into it.
var written = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);

var download = downloader.DownloadAsync(Url("/slow.png"), _dir.Path, null, new SyncProgress(progress), cancel.Token);
await started.Task.WaitAsync(TimeSpan.FromSeconds(10), TestContext.Current.CancellationToken);
await WaitUntil(() => Directory.GetFiles(_dir.Path).Length == 1);
var download = downloader.DownloadAsync(Url("/slow.png"), _dir.Path, null, new ProgressCallback(_ => written.TrySetResult()), cancel.Token);
await await Task.WhenAny(written.Task, download); // a download that fails before writing fails the test with its reason
Assert.Single(Directory.GetFiles(_dir.Path));
cancel.Cancel();

await Assert.ThrowsAnyAsync<OperationCanceledException>(() => download);
Assert.Empty(Directory.GetFiles(_dir.Path));
Assert.Empty(Directory.GetFiles(_dir.Path)); // deleted before the cancellation reaches the caller
}

[Fact]
Expand Down Expand Up @@ -295,11 +297,9 @@ public async Task Bytes_a_browser_handed_over_are_saved_like_a_download()
program.SaveAsync(_dir.Path, downloader, null, TestContext.Current.CancellationToken))).ErrorKey);
}

private static async Task WaitUntil(Func<bool> condition)
private sealed class ProgressCallback(Action<TransferProgress> report) : IProgress<TransferProgress>
{
var deadline = DateTime.UtcNow + TimeSpan.FromSeconds(10);
while (!condition() && DateTime.UtcNow < deadline)
await Task.Delay(10);
public void Report(TransferProgress value) => report(value);
}

private sealed class SyncProgress(List<TransferProgress> values) : IProgress<TransferProgress>
Expand Down
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