| name | code-testing-agent |
| description | Generates and writes new unit tests for any programming language using a Research-Plan-Implement pipeline. Use when asked to generate tests, write unit tests, add tests, improve test coverage, create test project, achieve high coverage, comprehensive tests, or asked to scaffold a new test project for an app, service, or library. Supports C#, TypeScript, JavaScript, Python, Go, Rust, Java, and more. Orchestrates the code-testing-generator sub-agent through research, planning, and implementation phases so tests compile, pass, and follow project conventions. DO NOT USE FOR: running existing tests or test filters (use run-tests); diagnosing coverage plateaus or project-wide coverage/CRAP analysis without writing tests (use coverage-analysis); targeted method/class CRAP scores (use crap-score); MSTest assertion guidance, MSTest test pattern modernization, or fixing existing MSTest test code (use writing-mstest-tests). |
| license | MIT |
Code Testing Generation Skill
An AI-powered skill that generates comprehensive, workable unit tests for any programming language using a coordinated multi-agent pipeline.
When to Use This Skill
Use this skill when you need to:
- Generate unit tests for an entire project or specific files
- Improve test coverage for existing codebases
- Create test files that follow project conventions
- Write tests that actually compile and pass
- Add tests for new features or untested code
When Not to Use
- Running or executing existing tests (use the
run-tests skill)
- Migrating between test frameworks (use migration skills)
- Writing tests specifically for MSTest patterns (use
writing-mstest-tests)
- Debugging failing test logic
How It Works
This skill coordinates multiple specialized agents in a Research → Plan → Implement pipeline:
Pipeline Overview
┌─────────────────────────────────────────────────────────────┐
│ TEST GENERATOR │
│ Coordinates the full pipeline and manages state │
└─────────────────────┬───────────────────────────────────────┘
│
┌─────────────┼─────────────┐
▼ ▼ ▼
┌───────────┐ ┌───────────┐ ┌───────────────┐
│ RESEARCHER│ │ PLANNER │ │ IMPLEMENTER │
│ │ │ │ │ │
│ Analyzes │ │ Creates │ │ Writes tests │
│ codebase │→ │ phased │→ │ per phase │
│ │ │ plan │ │ │
└───────────┘ └───────────┘ └───────┬───────┘
│
┌─────────┬───────┼───────────┐
▼ ▼ ▼ ▼
┌─────────┐ ┌───────┐ ┌───────┐ ┌───────┐
│ BUILDER │ │TESTER │ │ FIXER │ │LINTER │
│ │ │ │ │ │ │ │
│ Compiles│ │ Runs │ │ Fixes │ │Formats│
│ code │ │ tests │ │ errors│ │ code │
└─────────┘ └───────┘ └───────┘ └───────┘
Step-by-Step Instructions
Step 1: Determine the user request
Make sure you understand what user is asking and for what scope.
When the user does not express strong requirements for test style, coverage goals, or conventions, source the guidelines from unit-test-generation.prompt.md. This prompt provides best practices for discovering conventions, parameterization strategies, coverage goals (aim for 80%), and language-specific patterns.
Step 2: Invoke the Test Generator
Start by calling the code-testing-generator agent with your test generation request:
Generate unit tests for [path or description of what to test], following the [unit-test-generation.prompt.md](unit-test-generation.prompt.md) guidelines
The Test Generator will manage the entire pipeline automatically.
Step 3: Research Phase (Automatic)
The code-testing-researcher agent analyzes your codebase to understand:
- Language & Framework: Detects C#, TypeScript, Python, Go, Rust, Java, etc.
- Testing Framework: Identifies MSTest, xUnit, Jest, pytest, go test, etc.
- Project Structure: Maps source files, existing tests, and dependencies
- Build Commands: Discovers how to build and test the project
Output: .testagent/research.md
Step 4: Planning Phase (Automatic)
The code-testing-planner agent creates a structured implementation plan:
- Groups files into logical phases (2-5 phases typical)
- Prioritizes by complexity and dependencies
- Specifies test cases for each file
- Defines success criteria per phase
Output: .testagent/plan.md
Step 5: Implementation Phase (Automatic)
The code-testing-implementer agent executes each phase sequentially:
- Read source files to understand the API
- Write test files following project patterns
- Build using the
code-testing-builder sub-agent to verify compilation
- Test using the
code-testing-tester sub-agent to verify tests pass
- Fix using the
code-testing-fixer sub-agent if errors occur
- Lint using the
code-testing-linter sub-agent for code formatting
Each phase completes before the next begins, ensuring incremental progress.
Coverage Types
- Happy path: Valid inputs produce expected outputs
- Edge cases: Empty values, boundaries, special characters
- Error cases: Invalid inputs, null handling, exceptions
State Management
All pipeline state is stored in .testagent/ folder:
| File | Purpose |
|---|
.testagent/research.md | Codebase analysis results |
.testagent/plan.md | Phased implementation plan |
.testagent/status.md | Progress tracking (optional) |
Examples
Strategy Selection
The generator picks a strategy based on request scope:
| User Request | Strategy | Why |
|---|
"Generate tests for src/services/UserService.ts" | Direct | Single file, small scope — write tests immediately, skip sub-agents |
| "Add unit tests for my billing project" | Single pass | Moderate scope — one Research → Plan → Implement cycle covers it |
| "Achieve 80% coverage across the entire solution" | Iterative | Large scope — multiple R→P→I cycles, each narrowing remaining gaps |
Pipeline Walkthrough
Given a request like "Generate unit tests for my InvoiceService", the pipeline produces:
- Research →
.testagent/research.md containing detected language/framework, build commands, files to test ranked by priority, and existing test inventory
- Plan →
.testagent/plan.md containing phased approach with specific methods and test scenarios (happy path, edge cases, error cases) for each file
- Implement → Test files written, built, and verified per phase. Fix cycle runs automatically if build/test errors occur
- Validate → Full workspace build + full test run to catch cross-project issues
- Report → Summary of tests created, pass/fail counts, coverage notes, and next steps
Language-Specific Examples
The code-testing-extensions skill provides concrete, filled-in examples for each pipeline phase showing real source code, real research output, real plans, and real generated tests. Call the code-testing-extensions skill to discover available extension files, then read:
dotnet-examples.md — MSTest example with InvoiceService: research output, plan output, generated test file, fix cycle walkthrough, and final report
Agent Reference
| Agent | Purpose |
|---|
code-testing-generator | Coordinates pipeline |
code-testing-researcher | Analyzes codebase |
code-testing-planner | Creates test plan |
code-testing-implementer | Writes test files |
code-testing-builder | Compiles code |
code-testing-tester | Runs tests |
code-testing-fixer | Fixes errors |
code-testing-linter | Formats code |
Requirements
- Project must have a build/test system configured
- Testing framework should be installed (or installable)
- VS Code with GitHub Copilot extension
Troubleshooting
Tests don't compile
The code-testing-fixer agent will attempt to resolve compilation errors. Check .testagent/plan.md for the expected test structure. Call the code-testing-extensions skill and read the language-specific extension file for error code references (e.g., dotnet.md for .NET).
Tests fail
Most failures in generated tests are caused by wrong expected values in assertions, not production code bugs:
- Read the actual test output
- Read the production code to understand correct behavior
- Fix the assertion, not the production code
- Never mark tests
[Ignore] or [Skip] just to make them pass
Wrong testing framework detected
Specify your preferred framework in the initial request: "Generate Jest tests for..."
Environment-dependent tests fail
Tests that depend on external services, network endpoints, specific ports, or precise timing will fail in CI environments. Focus on unit tests with mocked dependencies instead.
Build fails on full solution
During phase implementation, build only the specific test project for speed. After all phases, run a full non-incremental workspace build to catch cross-project errors.
