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A Practical Testing Philosophy for Real-World Projects

TestingPhilosophyBest PracticesSoftware Development

A Practical Testing Philosophy for Real-World Projects

After years of writing tests in various codebases, I've developed a pragmatic philosophy that balances thorough testing with practical constraints. This isn't about perfect test coverage or rigid TDD—it's about testing strategies that actually work in the real world.

The Testing Pyramid, Revisited

The traditional testing pyramid (unit → integration → e2e) is useful, but I prefer to think in terms of confidence and cost:

High-Confidence, Low-Cost Tests

  • Pure functions with clear inputs/outputs
  • Business logic without external dependencies
  • Utility functions and data transformations
// This test gives high confidence at low cost
test('calculateTotal should apply discount correctly', () => {
  expect(calculateTotal([100, 200], 0.1)).toBe(270)
})

Medium-Confidence, Medium-Cost Tests

  • API endpoints with mocked dependencies
  • Component behavior with user interactions
  • Service layer integration

High-Cost, High-Impact Tests

  • Critical user journeys end-to-end
  • Payment flows
  • Authentication workflows

What I Don't Test (And Why)

Third-Party Libraries

I don't test that React renders correctly or that Axios makes HTTP requests. These libraries have their own test suites.

Trivial Code

// Don't test this
const getUserName = (user) => user.name

If it's a simple property access or trivial transformation, the test often costs more than the bug it would catch.

Implementation Details

I test behavior, not implementation. If I can refactor the code without changing the tests, that's a good sign.

Testing Strategies by Code Type

Business Logic

**Always test.** This is where bugs hurt most and tests provide the highest value.

UI Components

**Test user interactions and state changes, not styling.** Focus on what the user can do and what happens when they do it.

test('should show error message when form is submitted with invalid email', () => {
  render(<LoginForm />)
  fireEvent.change(screen.getByLabelText('Email'), { target: { value: 'invalid' } })
  fireEvent.click(screen.getByText('Submit'))
  expect(screen.getByText('Please enter a valid email')).toBeInTheDocument()
})

API Endpoints

**Test the happy path and key error scenarios.** Don't test every possible HTTP status code, but do test authentication, validation, and error handling.

The Confidence Heuristic

Before writing a test, I ask: "If this test passes, how confident am I that this feature works correctly?" If the answer is "not very," then either:

  • The test needs to be more comprehensive
  • The test isn't worth writing
  • I need a different type of test

Practical Guidelines

  • **Start with the riskiest parts** - What would cause the most damage if it broke?
  • **Test at the right level** - Don't test implementation details that could change
  • **Make tests readable** - Future you will thank you
  • **Keep tests fast** - Slow tests don't get run
  • **Accept imperfection** - 80% coverage of the right things beats 100% coverage of everything

The Reality Check

In the real world, you have deadlines, technical debt, and competing priorities. Perfect test coverage is rarely achievable or even desirable. The goal is strategic testing that gives you confidence to ship and refactor without fear.

Focus on testing what matters, and don't let perfect be the enemy of good enough.

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