Orphaned snapshots

A snapshot stays on disk when its test, or a case of it, is renamed or deleted. To find such snapshots, call OrphanedSnapshots.CheckAsync() once after all tests of the test project have run, in the teardown of your test framework:

xUnit v3

[assembly: AssemblyFixture(typeof(SnapshotCheck))]

public sealed class SnapshotCheck : IAsyncDisposable
{
    public async ValueTask DisposeAsync() => await OrphanedSnapshots.CheckAsync();
}

NUnit

[SetUpFixture]
public sealed class SnapshotCheck
{
    [OneTimeTearDown]
    public async Task CheckSnapshots() => await OrphanedSnapshots.CheckAsync();
}

MSTest

[TestClass]
public sealed class SnapshotCheck
{
    [AssemblyCleanup]
    public static async Task CheckSnapshots() => await OrphanedSnapshots.CheckAsync();
}

TUnit

public sealed class SnapshotCheck
{
    [After(TestSession)]
    public static async Task CheckSnapshots() => await OrphanedSnapshots.CheckAsync();
}

It fails when a snapshot or a pending file of the test project is not used by any MatchesSnapshot() of the test run, e.g. after the case "Let It Be" was removed from AlbumTests.Describes:

Failure message

Expected that every snapshot is used by a test of this run, but 1 snapshot was not used by any test:
  /src/Tests/AlbumTests.Describes.Let It Be.snapshot.txt

While accepting all changes (SnapshotAcceptance.All, see Accepting a snapshot), the orphaned snapshots and their pending files are deleted, and the check still fails, so that a deletion never goes unnoticed; SnapshotAcceptance.New only adds snapshots, so it keeps them:

Failure message

Expected that every snapshot is used by a test of this run, but 1 snapshot was not used by any test:
  /src/Tests/AlbumTests.Describes.Let It Be.snapshot.txt (deleted)

A test run that only runs some of the tests, e.g. a single test in the IDE, cannot be told apart from a complete one, so the check only runs on a build server (when CI, TF_BUILD, JENKINS_URL or TEAMCITY_VERSION is set), where the environment variable AWEXPECT_ACCEPT_SNAPSHOTS is ignored, so that it only reports. To check locally after running all tests, e.g. to delete the orphaned snapshots together with AWEXPECT_ACCEPT_SNAPSHOTS=all, force it:

await OrphanedSnapshots.CheckAsync(force: true);

Only the directory of the test project is searched, without bin, obj, hidden directories and the directories of other projects in it. A snapshot counts as used as soon as MatchesSnapshot() is called for it, even if it is not compared, e.g. after .Or was already met. The check cannot know about tests that did not reach MatchesSnapshot():

• A skipped test, or one that fails before calling MatchesSnapshot(), leaves its snapshot unused.
• A test that only exists for some target frameworks, e.g. behind #if NET8_0_OR_GREATER, leaves its snapshot unused in the test runs of the other target frameworks, so only check in the run of a target framework that has all tests.
• A snapshot per environment (see Snapshots per environment), e.g. AlbumTests.Describes@net48@windows.snapshot.txt, is only checked by a test run in that environment, here on Windows for net48; the test runs of the other environments skip it.
• A file name that only differs in case from a used snapshot counts as used, as it is the same file on Windows and macOS.
• Test projects that share a directory see each other's snapshots, so give each test project its own directory.