# Verify Email Snapshots

Snapshot test email templates using Verify to catch regressions.

- Repository: https://github.com/Aaronontheweb/dotnet-skills (1244 stars)
- Category: Testing
- License: MIT
- Last updated: 2026-10-28
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add Aaronontheweb/dotnet-skills --skill verify-email-snapshots -g -a claude-code -y`
Codex: `npx skills add Aaronontheweb/dotnet-skills --skill verify-email-snapshots -g -a codex -y`
Cursor: `npx skills add Aaronontheweb/dotnet-skills --skill verify-email-snapshots -g -a cursor -y`
Gemini CLI: `npx skills add Aaronontheweb/dotnet-skills --skill verify-email-snapshots -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add Aaronontheweb/dotnet-skills`

## Description

Snapshot test email templates using Verify to catch regressions. Validates rendered HTML output matches approved baseline. Works with MJML templates and any email renderer.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Snapshot Testing Email Templates with Verify

## When to Use This Skill

Use this skill when:
- Testing email template rendering for regressions
- Validating MJML templates compile to expected HTML
- Reviewing email changes in code review (diffs are visual)
- Ensuring variable substitution works correctly

**Related skills:**
- `aspnetcore/mjml-email-templates` - MJML template authoring
- `aspire/mailpit-integration` - Test email delivery locally
- `testing/snapshot-testing` - General Verify patterns

---

## Why Snapshot Test Emails?

Email templates are:
1. **Visual** - Small changes can break rendering across clients
2. **Hard to unit test** - Output is complex HTML, not simple values
3. **Prone to regression** - Template changes can have unintended effects

Snapshot testing captures the rendered HTML and fails when it changes unexpectedly.

---

## Installation

```bash
dotnet add package Verify.Xunit  # or Verify.NUnit, Verify.MSTest
```

---

## Basic Email Snapshot Test

```csharp
[Fact]
public async Task UserSignupInvitation_RendersCorrectly()
{
    // Arrange
    var renderer = _services.GetRequiredService<IMjmlTemplateRenderer>();

    var variables = new Dictionary<string, string>
    {
        { "PreviewText", "You've been invited to join Acme Corp" },
        { "OrganizationName", "Acme Corporation" },
        { "InviteeName", "John Doe" },
        { "InviterName", "Jane Admin" },
        { "InvitationLink", "https://example.com/invite/abc123" },
        { "ExpirationDate", "December 31, 2025" }
    };

    // Act
    var html = await renderer.RenderTemplateAsync(
        "UserInvitations/UserSignupInvitation",
        variables);

    // Assert
    await Verify(html, extension: "html");
}
```

This creates `UserSignupInvitation_RendersCorrectly.verified.html` on first run.

---

## Reviewing Email Changes

When a template changes, the test fails with a diff. Review options:

### 1. Visual Diff Tool

The rest: https://github.com/Aaronontheweb/dotnet-skills/blob/HEAD/skills/verify-email-snapshots/SKILL.md