TIA.js - Test Impact Analysis

Streamlined Test Impact Analysis for PR Workflows

TIA.js identifies exactly which tests need to run based on code changes, providing surgical precision for CI/CD optimization.

🚀 Quick Start

Installation

npm install -g @tia-js/cli
# or
yarn global add @tia-js/cli

PR Workflow

# 1. Detailed analysis for developers
tia line-analysis

# 2. Get affected tests for CI/CD
AFFECTED_TESTS=$(tia affected-tests --format specs)
cypress run --spec "$AFFECTED_TESTS"

📋 Commands

tia line-analysis

Provides detailed line-level analysis showing:

• Which specific lines changed
• Which tests cover those exact lines
• Coverage percentage of changed lines
• Uncovered lines that need testing

Example output:

📊 Line-Level Coverage Results
Summary:
  Total changed lines: 1
  Covered changed lines: 1  
  Coverage percentage: 100.0%
  Affected tests: 2

Tests Covering Changed Lines:
┌─────────────────────────────────────────────────────────────────────┐
│ Test Name → Covered Lines → Coverage %                           │
├─────────────────────────────────────────────────────────────────────┤
│ Dynamic Content Tests should load... 100.0% │
│   cypress/e2e/dynamic/content.cy.js             │
│   Lines: 17                                     │
└─────────────────────────────────────────────────────────────────────┘

tia affected-tests

Outputs affected tests for CI/CD integration:

# Get full test identifiers (includes individual test names)
tia affected-tests
# Output: cypress/e2e/dynamic/content.cy.js::Dynamic Content Tests should load...

# Get just test file names (for framework runners)
tia affected-tests --format specs  
# Output: cypress/e2e/dynamic/content.cy.js

# Detailed output for debugging
tia affected-tests --format detailed

🔧 Prerequisites

Coverage Data

TIA requires per-test coverage data in .tia/per-test-coverage/:

.tia/
└── per-test-coverage/
    ├── test_file_1__test_name_1.json
    ├── test_file_2__test_name_2.json
    └── ...

Production Setup:

1. Set up periodic job to run all tests against main branch
2. Collect per-test coverage data
3. Upload to TIA server
4. Sync to .tia/per-test-coverage/ before PR analysis

Supported Languages & Frameworks

JavaScript/TypeScript

• Frameworks: Jest, Cypress, Playwright
• Coverage: NYC/Istanbul format
• Test Patterns: *.test.js, *.spec.js, *.cy.js

Go

• Frameworks: Ginkgo, standard Go testing
• Coverage: Go coverage profiles converted to TIA format
• Test Patterns: *_test.go

Python

• Frameworks: pytest
• Coverage: coverage.py converted to TIA format
• Test Patterns: test_*.py, *_test.py

Git Repository

• Committed baseline (for change detection)
• Source files in appropriate directories (src/ for JS/TS, root for Go/Python)

🎯 How It Works

1. Change Detection: Uses git diff to identify modified lines
2. Coverage Mapping: Maps changed lines to test coverage data
3. Impact Analysis: Identifies which tests cover the specific changed lines
4. Surgical Precision: Only runs tests that actually cover your changes

🏗️ CI/CD Integration

GitHub Actions Example

- name: Get affected tests
  id: tia
  run: |
    # Sync coverage data from TIA server
    aws s3 sync s3://your-tia-bucket/.tia .tia/
    
    # Get affected tests
    AFFECTED_TESTS=$(tia affected-tests --format specs)
    echo "affected-tests=$AFFECTED_TESTS" >> $GITHUB_OUTPUT

- name: Run affected tests
  if: steps.tia.outputs.affected-tests != ''
  run: cypress run --spec "${{ steps.tia.outputs.affected-tests }}"

Jenkins Pipeline Example

pipeline {
  stages {
    stage('TIA Analysis') {
      steps {
        // Sync coverage data
        sh 'curl -o .tia.tar.gz https://your-tia-server/latest-coverage'
        sh 'tar -xzf .tia.tar.gz'
        
        // Get affected tests
        script {
          env.AFFECTED_TESTS = sh(
            script: 'tia affected-tests --format specs',
            returnStdout: true
          ).trim()
        }
      }
    }
    stage('Run Tests') {
      when { expression { env.AFFECTED_TESTS != '' } }
      steps {
        sh "cypress run --spec '${env.AFFECTED_TESTS}'"
      }
    }
  }
}

🧪 Framework Support

Currently supports:

• Cypress (E2E tests with webpack/babel instrumentation)
• Jest (Unit tests - coming soon)
• Playwright (E2E tests - coming soon)

📁 Directory Structure

your-project/
├── .tia/
│   ├── per-test-coverage/          # Synced from TIA server
│   └── coverage.json               # TIA storage (auto-generated)
├── src/                           # Source files to analyze
├── cypress/e2e/                  # Test files
└── package.json

⚡ Performance

• Fast: Only analyzes changed lines (not entire codebase)
• Precise: Line-level granularity eliminates false positives
• Scalable: Works with large codebases and test suites
• Lightweight: Minimal dependencies and fast startup

🔍 Troubleshooting

No coverage data found

ERROR: No coverage data found in .tia/per-test-coverage/

Solution: Sync coverage data from your TIA server before running analysis.

No affected tests

# Empty output from tia affected-tests

Causes:

• No tests cover the changed lines
• Coverage data is outdated
• Changes are in comments/non-executable code

Line analysis shows 0 changes

Solution: Ensure you have committed your baseline and made changes to source files in appropriate directories.

📚 Examples

TIA.js includes complete example applications for each supported language:

JavaScript/TypeScript Examples

• examples/basic-jest/ - Jest unit tests with TIA integration
• examples/cypress-e2e/ - Cypress E2E tests with per-test coverage collection

Go Examples

• examples/go-backend/ - Go REST API with Ginkgo tests
  • Gin web framework
  • Ginkgo BDD testing
  • TIA coverage reporter for Go

Python Examples

• examples/python-backend/ - Python Flask API with pytest
  • Flask REST API
  • pytest testing framework
  • TIA coverage plugin for Python

Each example includes:

• Complete application code
• Test setup with TIA integration
• Coverage collection configuration
• README with setup instructions

📖 Architecture

TIA.js uses line-level coverage mapping to provide surgical precision:

1. Build-time instrumentation (webpack/babel) tracks code coverage
2. Per-test collection stores individual test coverage profiles
3. Git diff parsing identifies exact changed lines
4. Coverage intersection maps changed lines to covering tests
5. Smart filtering eliminates false positives from bundling

License: Apache-2.0
Repository: https://github.com/your-org/tia-js