name: testing-patterns description: Testing patterns and principles. Unit, integration, mocking strategies.

Testing Patterns

Principles for reliable test suites.

1. Testing Pyramid

        /\          E2E (Few)
       /  \         Critical flows
      /----\
     /      \       Integration (Some)
    /--------\      API, DB queries
   /          \
  /------------\    Unit (Many)
                    Functions, classes

2. AAA Pattern

Step	Purpose
Arrange	Set up test data
Act	Execute code under test
Assert	Verify outcome

3. Test Type Selection

When to Use Each

Type	Best For	Speed
Unit	Pure functions, logic	Fast (<50ms)
Integration	API, DB, services	Medium
E2E	Critical user flows	Slow

4. Unit Test Principles

Good Unit Tests

Principle	Meaning
Fast	< 100ms each
Isolated	No external deps
Repeatable	Same result always
Self-checking	No manual verification
Timely	Written with code

What to Unit Test

Test	Don't Test
Business logic	Framework code
Edge cases	Third-party libs
Error handling	Simple getters

5. Integration Test Principles

What to Test

Area	Focus
API endpoints	Request/response
Database	Queries, transactions
External services	Contracts

Setup/Teardown

Phase	Action
Before All	Connect resources
Before Each	Reset state
After Each	Clean up
After All	Disconnect

6. Mocking Principles

When to Mock

Mock	Don't Mock
External APIs	The code under test
Database (unit)	Simple dependencies
Time/random	Pure functions
Network	In-memory stores

Mock Types

Type	Use
Stub	Return fixed values
Spy	Track calls
Mock	Set expectations
Fake	Simplified implementation

7. Test Organization

Naming

Pattern	Example
Should behavior	"should return error when..."
When condition	"when user not found..."
Given-when-then	"given X, when Y, then Z"

Grouping

Level	Use
describe	Group related tests
it/test	Individual case
beforeEach	Common setup

8. Test Data

Strategies

Approach	Use
Factories	Generate test data
Fixtures	Predefined datasets
Builders	Fluent object creation

Principles

Use realistic data
Randomize non-essential values (faker)
Share common fixtures
Keep data minimal

9. Best Practices

Practice	Why
One assert per test	Clear failure reason
Independent tests	No order dependency
Fast tests	Run frequently
Descriptive names	Self-documenting
Clean up	Avoid side effects

10. Anti-Patterns

❌ Don't	✅ Do
Test implementation	Test behavior
Duplicate test code	Use factories
Complex test setup	Simplify or split
Ignore flaky tests	Fix root cause
Skip cleanup	Reset state

Remember: Tests are documentation. If someone can't understand what the code does from the tests, rewrite them.

testing-patterns

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name: testing-patterns description: Testing patterns and principles. Unit, integration, mocking strategies.

Testing Patterns

1. Testing Pyramid

2. AAA Pattern

3. Test Type Selection

When to Use Each

4. Unit Test Principles

Good Unit Tests

What to Unit Test

5. Integration Test Principles

What to Test

Setup/Teardown

6. Mocking Principles

When to Mock

Mock Types

7. Test Organization

Naming

Grouping

8. Test Data

Strategies

Principles

9. Best Practices

10. Anti-Patterns

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