Understanding Mocha Test Hooks: Before, After, BeforeEach, AfterEach Quiz

Challenge your grasp of Mocha test hooks including before, after, beforeEach, and afterEach functions, and learn how these hooks structure test execution and handle setup and teardown tasks. This quiz is ideal for developers aiming to improve testing practices and knowledge of hooks in automated test frameworks.

1. Execution Order of Hooks

   When running a test suite with both beforeEach and afterEach hooks, in what order do the hooks and test cases typically execute?

   1. beforeEach → test case → afterEach
   2. beforeEach → afterEach → test case
   3. afterEach → test case → beforeEach
   4. test case → beforeEach → afterEach

   Explanation: The correct order is beforeEach → test case → afterEach. This ensures setup code in beforeEach runs before every test, followed by the test itself and then teardown, if any, in afterEach. The option where afterEach comes before the test case is incorrect because cleanup should happen after tests run, not before. The other orders either reverse the logical flow or incorrectly insert hooks after the test execution.

2. Purpose of Before Hook

   For a set of database tests requiring a connection to be established once before any tests run, which Mocha hook is most appropriate for the connection setup?

   1. before
   2. afterEach
   3. beforeEach
   4. test

   Explanation: The before hook is run once before any tests in the suite, making it ideal for initializing resources like database connections. beforeEach would repeat the setup for every test, which is inefficient. afterEach is meant for post-test cleanup, and 'test' is not a hook but an individual test case, so it cannot be used for global setup.

3. Global State Reset

   Which Mocha hook would you use to ensure that global variables are reset before each test case, preventing test interference due to shared state?

   1. beforeEach
   2. beforeAll
   3. after
   4. afterTest

   Explanation: beforeEach is specifically designed to run before every test, allowing you to reset state before each one executes. beforeAll is often confused with before but is not a valid hook name; the correct term is 'before'. after is for cleanup after all tests finish, and afterTest is not a recognized hook, so only beforeEach fits the requirement.

4. After Hook Responsibility

   After executing all test cases in a suite, what is the primary responsibility of the after hook?

   1. Perform one-time teardown operations
   2. Execute before any individual test
   3. Initialize test data for each test
   4. Skip remaining tests

   Explanation: The after hook handles one-time teardown or cleanup after all tests have run, such as closing a database or deleting temporary files. It does not run before tests, so 'Execute before any individual test' is incorrect. Initialization is handled by before or beforeEach, while skipping tests is not the responsibility of after.

5. Placement in Nested Describe Blocks

   In nested describe blocks, what is the scope of a beforeEach hook defined in the outer describe?

   1. It applies to all tests in both the outer and inner describe blocks.
   2. It only affects tests directly inside the outer describe block.
   3. It overrides beforeEach hooks in inner describe blocks.
   4. It stops inner describe blocks from running their own tests.

   Explanation: A beforeEach hook in an outer describe applies to every test case within its scope, including those in nested (inner) describe blocks. It does not override inner beforeEach hooks, as both will run in order. It affects more than just direct children, making the second option inaccurate. The last choice is incorrect because hooks do not prevent test execution.