The Testing Pyramid: Wrapping Up with CI/CD and Best Practices - Part 5

Software testing is more than writing a few unit tests and hoping for the best. To deliver reliable software, teams need a balanced testing strategy — one that combines Unit, Integration, and End-to-End (E2E) tests in the right proportions. This is where the Testing Pyramid comes in.

In this final part of our testing series, we’ll:

• Understand the Testing Pyramid model.
• Explore how to balance different types of tests.
• Learn how to integrate testing into CI/CD pipelines.
• Review best practices for building a sustainable testing culture.

The Testing Pyramid Explained

The Testing Pyramid (popularized by Mike Cohn) is a metaphor for structuring automated tests:

        ▲
        |   End-to-End (fewest, slowest)
        |
        |   Integration (moderate amount, balanced)
        |
        |   Unit Tests (largest base, fastest)
        ▼

1. Unit Tests (Foundation)

• Fast, cheap, and precise.
• Cover small pieces of logic in isolation.
• Should make up 60–70% of your automated test suite.

Example: Testing a function that calculates interest rates.

2. Integration Tests (Middle Layer)

• Validate how components interact.
• Cover database queries, API requests, or service orchestration.
• Should make up 20–30% of your test suite.

Example: Ensuring your API endpoint correctly fetches data from the database and formats the response.

3. End-to-End Tests (Top)

• Simulate real user flows across the full stack.
• Catch bugs unit or integration tests can’t.
• Should make up 10–15% of your suite (because they’re slow and expensive).

Example: A test where a user logs in, adds a product to their cart, and completes checkout.

Integrating Tests into CI/CD Pipelines

Automated tests are only valuable if they’re run consistently. Modern software teams embed them into CI/CD pipelines.

Step 1: Run Unit Tests Early

• Execute on every commit or pull request.
• Fail fast: block merges if unit tests fail.

Step 2: Run Integration Tests on Build/Deploy

• Run after the app compiles successfully.
• Can use a containerized test environment with mock or staging databases.

Step 3: Run End-to-End Tests on Staging

• Triggered before production deployment.
• Some teams run smoke E2E tests in production (carefully) to ensure critical flows still work.

Example CI/CD Flow (GitHub Actions / GitLab / Jenkins):

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Install dependencies
        run: npm install
      - name: Run unit tests
        run: npm test -- --unit
      - name: Run integration tests
        run: npm test -- --integration
      - name: Run e2e tests
        run: npm run test:e2e

Best Practices for a Balanced Testing Strategy

1. Follow the Pyramid, Not the Ice Cream Cone

• Too many E2E tests = slow, brittle pipeline.
• Too few unit tests = shaky foundation.
• Balance is key.

2. Use Test Doubles Wisely

• Mocks/Stubs in unit tests to isolate dependencies.
• Minimal mocking in integration tests — rely on real services where possible.

3. Make Tests Deterministic

• Tests should always produce the same result.
• Avoid flaky tests (caused by race conditions, timeouts, or external dependencies).

4. Keep Tests Fast

• Aim for seconds, not minutes.
• Developers won’t run slow tests locally.

5. Automate Everything in CI/CD

• Manual testing has its place, but regression checks must be automated.
• CI/CD pipelines should be your safety net before production.

6. Monitor and Improve Test Coverage

• Coverage isn’t everything, but low coverage usually indicates gaps.
• Focus on critical paths rather than chasing 100%.

7. Treat Tests as Code

• Tests should be maintainable, reviewed, and refactored like production code.
• Avoid “test rot” where tests become outdated or ignored.

Final Thoughts

The journey from unit → integration → E2E tests gives you confidence at every level of your system.

• Unit tests keep your building blocks solid.
• Integration tests ensure the blocks fit together.
• E2E tests confirm the entire structure works as intended.

By following the Testing Pyramid, integrating tests into CI/CD pipelines, and practicing discipline in writing effective tests, you’ll achieve:

• Faster feedback loops.
• Fewer production bugs.
• Higher developer confidence.
• Happier end-users.

Testing isn’t just about catching bugs, it’s about building trustworthy software at scale.

Next Steps for You:

• Audit your current test suite.
• See if you’re over-relying on one type of test.
• Gradually reshape your suite into a pyramid, not an ice cream cone.