lab-05.md

permalink	/labs/lab-05
title	Lab 05 - Code Quality Analysis with Copilot Agents
description	Measure test coverage, run the code-quality-detector to find quality issues, use the test-generator to create unit tests, and observe coverage improvement.

Overview

Duration	35 minutes
Level	Intermediate
Prerequisites	Lab 00, Lab 01, Lab 02

Learning Objectives

By the end of this lab, you will be able to:

• Run test coverage and understand the coverage gap in the sample app
• Run the code-quality-detector to find quality issues including coverage, complexity, and maintainability
• Use the test-generator to create unit tests for uncovered code
• Observe coverage improvement after applying generated tests

Exercises

Exercise 5.1: Measure Current Coverage

Before running any agents, establish a baseline by measuring the current test coverage.

1. Open a terminal in VS Code (Ctrl+`` ) and navigate to the sample app:

   cd sample-app

2. Run the test suite with coverage reporting:

   npm test -- --coverage

3. Review the coverage output. You should see coverage around 5% because only a placeholder test exists in __tests__/placeholder.test.ts.

4. Note the specific files and functions with 0% coverage. These are the targets for later exercises.

Exercise 5.2: Code Quality Detection

Use the Code Quality Detector agent to get a comprehensive quality analysis.

1. Open the Copilot Chat panel (Ctrl+Shift+I).

2. Type the following prompt:

   @code-quality-detector Analyze sample-app/ for code quality issues including coverage, complexity, and maintainability
   

3. Review the findings. The detector should identify issues such as:

   Finding	Category	File
   Test coverage below 80% threshold	Coverage	Project-wide
   High cyclomatic complexity	Complexity	sample-app/src/lib/utils.ts
   Use of any type annotations	Type Safety	Multiple files
   Code duplication in utility functions	Maintainability	sample-app/src/lib/
   Missing error handling	Reliability	sample-app/src/lib/db.ts

4. Note which findings the detector flags as highest priority. Low coverage and type safety issues are common starting points for improvement.

Exercise 5.3: Generate Tests

Use the Test Generator agent to create unit tests for one of the uncovered files.

1. In Copilot Chat, type:

   @test-generator Generate unit tests for sample-app/src/lib/utils.ts to improve coverage
   

2. Review the generated test file. The agent should produce tests that cover:

   • Each exported function in utils.ts
   • Edge cases (null inputs, empty strings, boundary values)
   • Expected return values for common inputs

3. Examine the test structure. The generated tests should use Jest syntax (describe, it, expect) consistent with the project configuration in jest.config.ts.

Exercise 5.4: Apply Tests and Re-measure (Optional)

Apply the generated tests and measure the coverage improvement.

1. Copy the generated test code into a new file:

   # Create the test file (paste the generated content)
   code sample-app/__tests__/utils.test.ts

2. Save the file with the generated test content from Exercise 5.3.

3. Re-run the test suite with coverage:

   cd sample-app
   npm test -- --coverage

4. Compare the new coverage percentage to the baseline from Exercise 5.1. You should see a measurable improvement in the coverage for src/lib/utils.ts.

5. This exercise demonstrates the detect → generate → verify cycle from Lab 02: the Code Quality Detector identified the gap, the Test Generator produced tests, and re-running coverage confirms the improvement.

Verification Checkpoint

Before proceeding, verify:

• You measured the baseline test coverage (approximately 5%)
• The code-quality-detector identified low coverage, complexity, or type safety issues
• The test-generator produced unit tests for utils.ts
• (Optional) You applied the generated tests and observed improved coverage
• You understand the detect → generate → verify cycle for code quality

Next Steps

Proceed to Lab 06.