snapshot-testing

Name: snapshot-testing
Author: Aaronontheweb

341installs98forks

How to install snapshot-testing?

aaronontheweb/dotnet-skills/snapshot-testing

$npx -y skills add Aaronontheweb/dotnet-skills --skill snapshot-testing

Installs into the current project.

Summary

Use Verify for snapshot testing in .NET. Approve API surfaces, HTTP responses, rendered emails, and serialized outputs. Detect unintended changes through human-reviewed baseline files.

Files · 1

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SKILL.md

1	# Snapshot Testing with Verify
2
3	## When to Use This Skill
4
5	Use snapshot testing when:
6	- Verifying rendered output (HTML emails, reports, generated code)
7	- Approving public API surfaces for breaking change detection
8	- Testing HTTP response bodies and headers
9	- Validating serialization output
10	- Catching unintended changes in complex objects
11
12	---
13
14	## What is Snapshot Testing?
15
16	Snapshot testing captures output and compares it against a human-approved baseline:
17
18	1. First run: Test generates a `.received.` file with actual output
19	2. Human review: Developer approves it, creating a `.verified.` file
20	3. Subsequent runs: Test compares output against `.verified.` file
21	4. Changes detected: Test fails, diff tool shows differences for review
22
23	This catches unintended changes while allowing intentional changes through explicit approval.
24
25	---
26
27	## Installation
28
29	### Add Verify Package
30
31	```bash
32	dotnet add package Verify.Xunit
33	# or for other test frameworks:
34	dotnet add package Verify.NUnit
35	dotnet add package Verify.MSTest
36	```
37
38	### Configure ModuleInitializer
39
40	Create a `ModuleInitializer.cs` in your test project:
41
42	```csharp
43	using System.Runtime.CompilerServices;
44
45	public static class ModuleInitializer
46	{
47	[ModuleInitializer]
48	public static void Init()
49	{
50	// Use source-file-relative paths for verified files
51	VerifyBase.UseProjectRelativeDirectory("Snapshots");
52
53	// Configure diff tool (optional - auto-detected)
54	// DiffTools.UseOrder(DiffTool.Rider, DiffTool.VisualStudioCode);
55	}
56	}
57	```
58
59	---
60
61	## Basic Usage
62
63	### Simple Object Verification
64
65	```csharp
66	[Fact]
67	public Task VerifyUserDto()
68	{
69	var user = new UserDto(
70	Id: "user-123",
71	Name: "John Doe",
72	Email: "john@example.com",
73	CreatedAt: new DateTime(2025, 1, 15));
74
75	return Verify(user);
76	}
77	```
78
79	Creates `VerifyUserDto.verified.txt`:
80	```json
81	{
82	Id: user-123,
83	Name: John Doe,
84	Email: john@example.com,
85	CreatedAt: 2025-01-15T00:00:00
86	}
87	```
88
89	### String/HTML Verification
90
91	```csharp
92	[Fact]
93	public async Task VerifyRenderedEmail()
94	{
95	var html = await _emailRenderer.RenderAsync("Welcome", new { Name = "John" });
96
97	// Use extension parameter for proper file naming
98	await Verify(html, extension: "html");
99	}
100	```
101
102	Creates `VerifyRenderedEmail.verified.html` - viewable in browser.
103
104	---
105
106	## Email Template Testing
107
108	Use Verify to catch unintended changes in rendered email templates:
109
110	```csharp
111	[Fact]
112	public async Task UserSignupInvitation_RendersCorrectly()
113	{
114	var renderer = _services.GetRequiredService<IMjmlTemplateRenderer>();
115
116	var variables = new Dictionary<string, string>
117	{
118	{ "OrganizationName", "Acme Corporation" },
119	{ "InviteeName", "John Doe" },
120	{ "InviterName", "Jane Admin" },
121	{ "InvitationLink", "https://example.com/invite/abc123" },
122	{ "ExpirationDate", "December 31, 2025" }
123	};
124
125	var html = await renderer.RenderTemplateAsync(
126	"UserInvitations/UserSignupInvitation",
127	variables);
128
129	await Verify(html, extension: "html");
130	}
131	```
132
133	Benefits for email testing:
134	- Catches CSS/layout regressions
135	- Detects broken template variables
136	- Visual review in diff tool
137	- Version control tracks email changes
138
139	---
140
141	## API Surface Approval
142
143	Prevent accidental breaking changes to public APIs:
144
145	```csharp
146	[Fact]
147	public Task ApprovePublicApi()
148	{
149	var assembly = typeof(MyLibrary.PublicClass).Assembly;
150
151	var publicApi = assembly.GetExportedTypes()
152	.OrderBy(t => t.FullName)
153	.Select(t => new
154	{
155	Type = t.FullName,
156	Members = t.GetMembers(BindingFlags.Public \| BindingFlags.Instance \| BindingFlags.Static)
157	.Where(m => m.DeclaringType == t)
158	.OrderBy(m => m.Name)
159	.Select(m => m.ToString())
160	});
161
162	return Verify(publicApi);
163	}
164	```
165
166	Or use the dedicated ApiApprover package:
167
168	```bash
169	dotnet add package PublicApiGenerator
170	dotnet add package Verify.Xunit
171	```
172
173	```csharp
174	[Fact]
175	public Task ApproveApi()
176	{
177	var api = typeof(MyPublicClass).Assembly.GeneratePublicApi();
178	return Verify(api);
179	}
180	```
181
182	Creates `.verified.txt` with full API surface - any change requires explicit approval.
183
184	---
185
186	## HTTP Response Testing
187
188	```csharp
189	[Fact]
190	public async Task GetUser_ReturnsExpectedResponse()
191	{
192	var client = _factory.CreateClient();
193
194	var response = await client.GetAsync("/api/users/123");
195
196	// Verify status, headers, and body together
197	await Verify(new
198	{
199	StatusCode = response.StatusCode,
200	Headers = response.Headers
201	.Where(h => h.Key.StartsWith("X-")) // Custom headers only
202	.ToDictionary(h => h.Key, h => h.Value.First()),
203	Body = await response.Conten

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Type

snapshot-testing

341installs98forks

View on GitHub

How to install snapshot-testing?

aaronontheweb/dotnet-skills/snapshot-testing

$npx -y skills add Aaronontheweb/dotnet-skills --skill snapshot-testing

Installs into the current project.

Summary

Use Verify for snapshot testing in .NET. Approve API surfaces, HTTP responses, rendered emails, and serialized outputs. Detect unintended changes through human-reviewed baseline files.

Files · 1

View on GitHub

SKILL.md

1	# Snapshot Testing with Verify
2
3	## When to Use This Skill
4
5	Use snapshot testing when:
6	- Verifying rendered output (HTML emails, reports, generated code)
7	- Approving public API surfaces for breaking change detection
8	- Testing HTTP response bodies and headers
9	- Validating serialization output
10	- Catching unintended changes in complex objects
11
12	---
13
14	## What is Snapshot Testing?
15
16	Snapshot testing captures output and compares it against a human-approved baseline:
17
18	1. First run: Test generates a `.received.` file with actual output
19	2. Human review: Developer approves it, creating a `.verified.` file
20	3. Subsequent runs: Test compares output against `.verified.` file
21	4. Changes detected: Test fails, diff tool shows differences for review
22
23	This catches unintended changes while allowing intentional changes through explicit approval.
24
25	---
26
27	## Installation
28
29	### Add Verify Package
30
31	```bash
32	dotnet add package Verify.Xunit
33	# or for other test frameworks:
34	dotnet add package Verify.NUnit
35	dotnet add package Verify.MSTest
36	```
37
38	### Configure ModuleInitializer
39
40	Create a `ModuleInitializer.cs` in your test project:
41
42	```csharp
43	using System.Runtime.CompilerServices;
44
45	public static class ModuleInitializer
46	{
47	[ModuleInitializer]
48	public static void Init()
49	{
50	// Use source-file-relative paths for verified files
51	VerifyBase.UseProjectRelativeDirectory("Snapshots");
52
53	// Configure diff tool (optional - auto-detected)
54	// DiffTools.UseOrder(DiffTool.Rider, DiffTool.VisualStudioCode);
55	}
56	}
57	```
58
59	---
60
61	## Basic Usage
62
63	### Simple Object Verification
64
65	```csharp
66	[Fact]
67	public Task VerifyUserDto()
68	{
69	var user = new UserDto(
70	Id: "user-123",
71	Name: "John Doe",
72	Email: "john@example.com",
73	CreatedAt: new DateTime(2025, 1, 15));
74
75	return Verify(user);
76	}
77	```
78
79	Creates `VerifyUserDto.verified.txt`:
80	```json
81	{
82	Id: user-123,
83	Name: John Doe,
84	Email: john@example.com,
85	CreatedAt: 2025-01-15T00:00:00
86	}
87	```
88
89	### String/HTML Verification
90
91	```csharp
92	[Fact]
93	public async Task VerifyRenderedEmail()
94	{
95	var html = await _emailRenderer.RenderAsync("Welcome", new { Name = "John" });
96
97	// Use extension parameter for proper file naming
98	await Verify(html, extension: "html");
99	}
100	```
101
102	Creates `VerifyRenderedEmail.verified.html` - viewable in browser.
103
104	---
105
106	## Email Template Testing
107
108	Use Verify to catch unintended changes in rendered email templates:
109
110	```csharp
111	[Fact]
112	public async Task UserSignupInvitation_RendersCorrectly()
113	{
114	var renderer = _services.GetRequiredService<IMjmlTemplateRenderer>();
115
116	var variables = new Dictionary<string, string>
117	{
118	{ "OrganizationName", "Acme Corporation" },
119	{ "InviteeName", "John Doe" },
120	{ "InviterName", "Jane Admin" },
121	{ "InvitationLink", "https://example.com/invite/abc123" },
122	{ "ExpirationDate", "December 31, 2025" }
123	};
124
125	var html = await renderer.RenderTemplateAsync(
126	"UserInvitations/UserSignupInvitation",
127	variables);
128
129	await Verify(html, extension: "html");
130	}
131	```
132
133	Benefits for email testing:
134	- Catches CSS/layout regressions
135	- Detects broken template variables
136	- Visual review in diff tool
137	- Version control tracks email changes
138
139	---
140
141	## API Surface Approval
142
143	Prevent accidental breaking changes to public APIs:
144
145	```csharp
146	[Fact]
147	public Task ApprovePublicApi()
148	{
149	var assembly = typeof(MyLibrary.PublicClass).Assembly;
150
151	var publicApi = assembly.GetExportedTypes()
152	.OrderBy(t => t.FullName)
153	.Select(t => new
154	{
155	Type = t.FullName,
156	Members = t.GetMembers(BindingFlags.Public \| BindingFlags.Instance \| BindingFlags.Static)
157	.Where(m => m.DeclaringType == t)
158	.OrderBy(m => m.Name)
159	.Select(m => m.ToString())
160	});
161
162	return Verify(publicApi);
163	}
164	```
165
166	Or use the dedicated ApiApprover package:
167
168	```bash
169	dotnet add package PublicApiGenerator
170	dotnet add package Verify.Xunit
171	```
172
173	```csharp
174	[Fact]
175	public Task ApproveApi()
176	{
177	var api = typeof(MyPublicClass).Assembly.GeneratePublicApi();
178	return Verify(api);
179	}
180	```
181
182	Creates `.verified.txt` with full API surface - any change requires explicit approval.
183
184	---
185
186	## HTTP Response Testing
187
188	```csharp
189	[Fact]
190	public async Task GetUser_ReturnsExpectedResponse()
191	{
192	var client = _factory.CreateClient();
193
194	var response = await client.GetAsync("/api/users/123");
195
196	// Verify status, headers, and body together
197	await Verify(new
198	{
199	StatusCode = response.StatusCode,
200	Headers = response.Headers
201	.Where(h => h.Key.StartsWith("X-")) // Custom headers only
202	.ToDictionary(h => h.Key, h => h.Value.First()),
203	Body = await response.Conten

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Type