Snapshot Testing

This walks you through Verify, the .NET snapshot testing library that's genuinely useful for catching regressions in rendered output. Instead of writing a dozen assertions for complex objects, you approve a baseline file once and the test fails if anything changes. The guide covers the practical stuff: rendering email templates to HTML and diffing them visually, approving your public API surface to prevent accidental breaking changes, scrubbing timestamps and GUIDs so tests aren't flaky, and setting up CI so you're not manually clicking through diff tools in your pipeline. If you're testing anything with non-trivial output like HTTP responses or serialized data, this is worth the setup cost.