code-testing-agent

SKILL.md

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.