Reporters

A reporter is told about the outcome of every snapshot, e.g. to open a diff tool or to collect the changed snapshots of a test run. Derive from SnapshotReporter in the namespace aweXpect.Snapshots and add it to the reporters:

public sealed class ChangedSnapshotsReporter : SnapshotReporter
{
    public ConcurrentBag<SnapshotId> Changed { get; } = new();

    public override ValueTask OnMismatchAsync(SnapshotMismatch mismatch, CancellationToken cancellationToken)
    {
        Changed.Add(mismatch.Id);
        return default;
    }
}

Customize.aweXpect.Global.Snapshots().Reporters.Set([
    .. Customize.aweXpect.Global.Snapshots().Reporters.Get(),
    new ChangedSnapshotsReporter(),
]);

Member	Called
OnMismatchAsync	after the store recorded a missing or different snapshot, e.g. wrote the pending file
OnMatchAsync	when the snapshot matches, before the store records the match, e.g. deletes a leftover pending file

Like the pending file, a mismatch is only reported when the whole expectation fails, e.g. not when another branch of an .Or is met, and not for a negated snapshot. An accepted change is not reported, as it needs no review. Several reporters are called in the order of the list, and never on a build server, the same detection as for accepting changes. An exception of a reporter never changes the result of the test.

SnapshotMismatch has the Id and the Store of the snapshot, the reviewed Snapshot (null when it did not exist) and the Actual value, after the rules of the expectation were applied, e.g. with masked GUIDs. Both are a SnapshotContent with the Bytes as the store keeps them (text as UTF-8 with an additional final line break), and, unless it is binary data, the Text that was compared (IsText). SnapshotMatch has the Id and the Store.

The reporter is not told about files, as a store need not keep any. A store that keeps the snapshots in files, like the default store, implements IFileSnapshotStore, whose GetSnapshotFile(id) and GetPendingFile(id) return their paths:

if (mismatch.Store is IFileSnapshotStore files)
{
    Console.WriteLine($"Review {files.GetPendingFile(mismatch.Id)}");
}

Exceptions of a reporter

An exception of a reporter is written to the trace writer of Customize.aweXpect.EnableTracing(…) and otherwise ignored.