Interview Questions
Mocha provides four types of hooks: 1) before() - runs once before all tests, 2) beforeEach() - runs before each test, 3) after() - runs once after all tests, 4) afterEach() - runs after each test. Hooks help with setup and cleanup operations.
Async hooks can be handled through: 1) done callback, 2) returning promises, 3) async/await syntax, 4) proper error handling, 5) timeout management. Example: beforeEach(async () => { await setupDatabase(); });
Hook execution order: 1) before() at suite level, 2) beforeEach() from outer to inner, 3) test execution, 4) afterEach() from inner to outer, 5) after() at suite level. Understanding order is crucial for proper setup/cleanup.
Context sharing methods: 1) Using this keyword, 2) Shared variables in closure, 3) Hook-specific context objects, 4) Global test context, 5) Proper scoping of shared resources. Example: beforeEach(function() { this.sharedData = 'test'; });
describe blocks serve to: 1) Group related tests, 2) Create test hierarchy, 3) Share setup/teardown code, 4) Organize test suites, 5) Provide context for tests. Helps maintain clear test structure.
Cleanup handling: 1) Use afterEach/after hooks, 2) Clean shared resources, 3) Reset state between tests, 4) Handle async cleanup, 5) Ensure proper error handling. Important for test isolation.
Root level hooks: 1) Apply to all test files, 2) Set up global before/after hooks, 3) Handle common setup/teardown, 4) Manage shared resources, 5) Configure test environment. Used for project-wide setup.
Hook error handling: 1) Try-catch blocks in hooks, 2) Promise error handling, 3) Error reporting in hooks, 4) Cleanup after errors, 5) Proper test failure handling. Ensures reliable test execution.
Hook best practices: 1) Keep hooks focused, 2) Minimize hook complexity, 3) Clean up resources properly, 4) Handle async operations correctly, 5) Maintain hook independence. Improves test maintainability.
Hook timeout handling: 1) Set hook-specific timeouts, 2) Configure global timeouts, 3) Handle async timeouts, 4) Manage long-running operations, 5) Proper timeout error handling. Example: before(function() { this.timeout(5000); });
Nested describes: 1) Create test hierarchies, 2) Share context between levels, 3) Organize related tests, 4) Handle nested hooks properly, 5) Maintain clear structure. Helps organize complex test suites.
Fixture sharing patterns: 1) Use before hooks for setup, 2) Implement fixture factories, 3) Share through context, 4) Manage fixture lifecycle, 5) Clean up fixtures properly. Ensures consistent test data.
Dynamic test generation: 1) Generate tests in loops, 2) Create tests from data, 3) Handle dynamic describes, 4) Manage test context, 5) Ensure proper isolation. Useful for data-driven tests.
State management strategies: 1) Use hooks for state setup, 2) Clean state between tests, 3) Isolate test state, 4) Handle shared state, 5) Manage state dependencies. Important for test reliability.
Test helper implementation: 1) Create helper functions, 2) Share common utilities, 3) Manage helper state, 4) Handle helper errors, 5) Document helper usage. Improves test code reuse.
Async hook patterns: 1) Handle promise chains, 2) Manage async operations, 3) Control execution flow, 4) Handle timeouts, 5) Proper error handling. Important for reliable async setup/teardown.
Large suite organization: 1) Group by feature/module, 2) Use nested describes, 3) Share common setup, 4) Maintain clear structure, 5) Document organization. Improves test maintainability.
Error handling practices: 1) Proper try-catch usage, 2) Error reporting in hooks, 3) Cleanup after errors, 4) Error propagation handling, 5) Test failure management. Ensures reliable test execution.
Conditional test handling: 1) Skip tests conditionally, 2) Run specific tests, 3) Handle environment conditions, 4) Manage test flags, 5) Document conditions. Enables flexible test execution.
Hook composition patterns: 1) Combine multiple hooks, 2) Share hook functionality, 3) Create reusable hooks, 4) Manage hook dependencies, 5) Handle hook ordering. Enables modular test setup.
Advanced patterns: 1) Custom test structures, 2) Dynamic suite generation, 3) Complex test hierarchies, 4) Shared behavior patterns, 5) Test composition strategies. Enables sophisticated test organization.
Complex workflow testing: 1) Break down into steps, 2) Manage state transitions, 3) Handle async flows, 4) Test error paths, 5) Verify workflow completion. Ensures comprehensive testing.
Suite inheritance: 1) Share common tests, 2) Extend base suites, 3) Override specific tests, 4) Manage shared context, 5) Handle hook inheritance. Enables test reuse.
State machine testing: 1) Test state transitions, 2) Verify state invariants, 3) Test invalid states, 4) Handle async states, 5) Test state history. Ensures proper state handling.
Custom interfaces: 1) Define interface API, 2) Implement test organization, 3) Handle hook integration, 4) Manage context, 5) Support async operations. Enables custom testing patterns.
Distributed testing: 1) Coordinate multiple components, 2) Handle async communication, 3) Test system integration, 4) Manage distributed state, 5) Test failure scenarios. Ensures system-wide testing.
Advanced hook patterns: 1) Dynamic hook generation, 2) Conditional hook execution, 3) Hook composition, 4) Hook middleware, 5) Hook state management. Enables sophisticated setup/teardown.