verify-email-snapshots

1# Snapshot Testing Email Templates with Verify
2 
3## When to Use This Skill
4 
5Use this skill when:
6- Testing email template rendering for regressions
7- Validating MJML templates compile to expected HTML
8- Reviewing email changes in code review (diffs are visual)
9- Ensuring variable substitution works correctly
10 
11**Related skills:**
12- `aspnetcore/mjml-email-templates` - MJML template authoring
13- `aspire/mailpit-integration` - Test email delivery locally
14- `testing/snapshot-testing` - General Verify patterns
15 
16---
17 
18## Why Snapshot Test Emails?
19 
20Email templates are:
211. **Visual** - Small changes can break rendering across clients
222. **Hard to unit test** - Output is complex HTML, not simple values
233. **Prone to regression** - Template changes can have unintended effects
24 
25Snapshot testing captures the rendered HTML and fails when it changes unexpectedly.
26 
27---
28 
29## Installation
30 
31```bash
32dotnet add package Verify.Xunit  # or Verify.NUnit, Verify.MSTest
33```
34 
35---
36 
37## Basic Email Snapshot Test
38 
39```csharp
40[Fact]
41public async Task UserSignupInvitation_RendersCorrectly()
42{
43    // Arrange
44    var renderer = _services.GetRequiredService<IMjmlTemplateRenderer>();
45 
46    var variables = new Dictionary<string, string>
47    {
48        { "PreviewText", "You've been invited to join Acme Corp" },
49        { "OrganizationName", "Acme Corporation" },
50        { "InviteeName", "John Doe" },
51        { "InviterName", "Jane Admin" },
52        { "InvitationLink", "https://example.com/invite/abc123" },
53…