.NET Testing Fundamentals Overview

Source: kevintsengtw/​dotnet-testing-agent-skills (MIT). Ported into dotnet-agent-harness.

.NET Testing Fundamentals Overview

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🤖 AI Agent Important Notes

When you (AI Agent) are loaded with this entry skill, please read the following guidelines first:

📋 Positioning of This Skill

This file is a "navigation center" used to help find the correct sub-skills.

Your Tasks Are

1. ✅ Match corresponding sub-skills based on user needs
2. ✅ Use the Skill tool to load specific sub-skills
3. ✅ Let sub-skills provide professional testing guidance

Prohibited Behaviors

• ❌ Do not provide test code directly in this entry skill
• ❌ Do not start implementing tests without loading sub-skills
• ❌ Do not skip sub-skills to provide "general" testing advice

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🎯 Quick Skill Reference Table (AI Agent Must Read)

Keywords mentioned by users → Sub-skills to load

Most Frequently Used Skills (Must Memorize)

Basic Entry Skills

Advanced Skill Combinations

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⚠️ Usage Flow Examples

✅ Correct Flow

User: Please help me create tests for CreateUserValidator

AI: I notice you need to test a Validator. According to the quick reference table,
    I should load the dotnet-testing-fluentvalidation-testing skill.

    [Use Skill tool to load sub-skill]

AI: Now following the FluentValidation Testing skill guidelines to create tests for you...

❌ Incorrect Flow

User: Please help me create tests for CreateUserValidator

AI: Okay, let me write the tests... (start writing code directly without loading sub-skills)

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📚 Complete Skill List

To view the complete list of 19 fundamental skills, detailed decision trees, and learning path recommendations, please continue reading the subsequent content of this file.

Human Developer Reference: For quick lookup, please check SKILLS_QUICK_INDEX.md

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Applicable Scenarios

When you encounter the following situations, I will help you find the correct skills:

• Just starting to learn .NET testing, don't know where to begin
• Want to create tests for existing projects, need complete guidance
• Need to improve test quality, looking for best practices
• Encounter specific testing scenarios, unsure which tool to use
• Want to learn about test data generation, assertions, mocking, and other technologies
• Hope to improve test readability and maintainability
• Need to handle special testing scenarios like time, file systems, etc.

Quick Decision Tree

Where Should I Start?

Scenario 1: Complete Beginner, Never Written Tests Before

Recommended Learning Path:

1. dotnet-testing-unit-test-fundamentals - Understand FIRST principles and 3A Pattern
2. dotnet-testing-test-naming-conventions - Learn naming conventions
3. dotnet-testing-xunit-project-setup - Create your first test project

Why This Path:

• FIRST principles are the foundation of all tests, establish correct concepts first
• Naming conventions make tests readable and maintainable
• Hands-on project creation transforms theory into practice

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Scenario 2: Can Write Basic Tests, But Test Data Preparation Is Troublesome

Recommended Skills (Choose One or Combine):

Option A - Automation First

→ dotnet-testing-autofixture-basics Suitable: Need large amounts of test data, reduce boilerplate code

Option B - Realistic Data First

→ dotnet-testing-bogus-fake-data Suitable: Need realistic test data (names, addresses, emails, etc.)

Option C - Semantic Clarity First

→ dotnet-testing-test-data-builder-pattern Suitable: Need high readability, clear expression of test intent

Option D - Best of Both

→ dotnet-testing-autofixture-basics + dotnet-testing-autofixture-bogus-integration Suitable: Need both automation and realistic data

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Scenario 3: Have External Dependencies (Database, API, Third-party Services) Need to Mock

Recommended Skill Combination:

1. dotnet-testing-nsubstitute-mocking - NSubstitute Mock framework fundamentals
2. dotnet-testing-autofixture-nsubstitute-integration - (Optional) Integrate AutoFixture with NSubstitute

When Is the Second Skill Needed:

• If you are already using AutoFixture to generate test data
• Want to automatically create Mock objects, reduce manual configuration

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Scenario 4: Special Scenarios in Testing

Time-related Testing

→ dotnet-testing-datetime-testing-timeprovider Handles: DateTime.Now, timezone conversion, time calculations

File System Testing

→ dotnet-testing-filesystem-testing-abstractions Handles: File read/​write, directory operations, path handling

Private/​Internal Member Testing

→ dotnet-testing-private-internal-testing Handles: Need to test private, internal members (but use cautiously)

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Scenario 5: Need Better Assertion Methods

Basic Needs - Fluent Assertions

→ dotnet-testing-awesome-assertions-guide Should be used by all projects to improve test readability

Advanced Needs - Complex Object Comparison

→ dotnet-testing-complex-object-comparison Handles: Deep object comparison, DTO validation, Entity comparison

Validation Rule Testing

→ dotnet-testing-fluentvalidation-testing Handles: Testing FluentValidation validators

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Scenario 6: Want to Learn About Test Coverage

→ dotnet-testing-code-coverage-analysis Learn: Use Coverlet to analyze code coverage, generate reports

Skill Classification Map

Divide 19 fundamental skills into 7 categories (testing fundamentals, test data generation, test doubles, assertion validation, special scenarios, test metrics, framework integration), each containing skill reference tables, learning paths, and code examples.

📖 For details, please refer to references/​skill-classification-map.md

Common Task Mapping Table

Provide 7 common testing tasks (create project from scratch, service dependency testing, time logic testing, etc.) with skill combination recommendations, implementation steps, and prompt examples.

📖 For details, please refer to references/​task-mapping-table.md

Learning Path Recommendations

Plan daily learning schedules for beginner path (1-2 weeks) and advanced path (2-3 weeks), including skills, learning focuses, and practical exercises.

📖 For details, please refer to references/​learning-paths.md

Guided Conversation Examples

Show how AI interacts with you to help choose the correct skills, including 4 common conversation scenarios: beginner entry, handling dependencies, specific problems, improving tests.

📖 For details, please refer to references/​conversation-examples.md

Relationship with Advanced Skills

After completing fundamental skills, if you need integration testing, API testing, containerized testing, or microservice testing, please refer to:

Advanced Integration Testing → dotnet-testing-advanced

• ASP.NET Core integration testing
• Containerized testing (Testcontainers)
• Microservice testing (.NET Aspire)
• Test framework upgrades and migrations

Related Resources

Original Data Sources

• iThome Ironman Competition Series: Old School Software Engineer's Testing Practice - 30 Day Challenge 🏆 2025 iThome Ironman Competition Software Development Group Champion

• Complete Sample Code: 30Days_in_Testing_Samples Contains executable code for all sample projects

Learning Documents

This skill set is refined from the following complete materials:

• Agent Skills: From Architecture Design to Practical Application (docs/​Agent_Skills_Mastery.pdf) Complete coverage of Agent Skills from theory to practice

• Claude Code Skills: Making AI a Professional Craftsman (docs/​Agent_Skills_Architecture.pdf) In-depth analysis of Agent Skills architecture design

• .NET Testing: Write Better, Run Faster (docs/​NET_Testing_Write_Better_Run_Faster.pdf) Test execution optimization and debugging techniques

Next Steps

Choose the skill that matches your needs to start learning, or tell me your specific situation and I will recommend the most suitable learning path!

Quick Start:

• Beginner → Start with dotnet-testing-unit-test-fundamentals
• Experienced → Tell me the specific problems you encounter
• Unsure → Tell me your project situation and I will help you analyze