What is snapshot testing for emails?

Snapshot testing captures the rendered HTML of an email template and saves it as a 'verified' baseline file. Future test runs compare new output against this file to detect unintended visual or structural changes.

How do I handle dynamic data like timestamps in my tests?

The skill provides patterns for 'scrubbing,' which automatically replaces dynamic values like dates, GUIDs, or tokens with static placeholders so the snapshots remain consistent across test runs.

How do I review a failed email snapshot test?

When a test fails, you can use the Verify diff tool to see a side-by-side code comparison, or open the '.received.html' file in a browser to see the actual rendered email.

Does this skill support MJML?

Yes, it is designed to work with MJML renderers, allowing you to verify that your MJML source compiles into the correct HTML across different versions.

Which .NET testing frameworks are compatible?

This skill supports the most common .NET testing libraries including Xunit, NUnit, and MSTest via the Verify library ecosystem.

Verify Email Snapshots

Name: Verify Email Snapshots
Author: Aaronontheweb

byAaronontheweb

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423

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Security & Testing

Automates visual regression testing for email templates by capturing and comparing rendered HTML snapshots in .NET applications.

This skill streamlines the testing of email templates in .NET applications by leveraging the Verify snapshot testing library. It allows developers to capture the exact HTML output of rendered templates—including those built with MJML—and automatically flags regressions when changes occur. By providing tools for visual diffing, browser previews, and dynamic value scrubbing (like timestamps or GUIDs), it ensures that email communication remains consistent and bug-free across updates, significantly reducing the manual effort required to validate complex HTML layouts during code reviews.

Key Features

01CI/CD integration support to prevent accidental baseline changes in production pipelines

02Visual diffing and browser-based review of template changes

03423 GitHub stars

04Snapshot-based regression testing for HTML and MJML email templates

05Integration with popular .NET test frameworks including Xunit, NUnit, and MSTest

06Automatic scrubbing of dynamic values like dates, GUIDs, and tokens to ensure deterministic tests

Use Cases

01Ensuring correct variable substitution in complex transactional emails like invoices and invitations

02Validating that MJML template changes compile to the expected HTML layout

03Reviewing visual changes to email layouts during pull requests using automated snapshot diffs

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add aaronontheweb/dotnet-skills verify-email-snapshots

For use in Claude.ai and ChatGPT

Download Skill