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-=== Purpose === |
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+### Purpose |
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-* Mocking simplifies unit testing by replacing the dependencies of the unit being tested with simplified, simulated versions called mocks. |
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-* Example: Consider a unit under test that relies on a database. In testing, the database can be mocked to return a static value, eliminating the need for an actual database. |
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+* **Mocking simplifies unit testing by replacing the dependencies** of the unit being tested with simplified, simulated versions called mocks. Example: Consider a unit under test that relies on a database. In testing, the database can be mocked to return a static value, eliminating the need for an actual database. |
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+### Benefits of Mocking |
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-=== Benefits of Mocking === |
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- |
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* Isolation of units to test each unit separately, dramatically reducing complexity and increasing test execution speed by replacing loaded modules with mocks. |
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* Simplifies the re-creation of specific scenarios (use cases, boundary cases). |
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* Expose hidden internals of production code without compromising encapsulation. |
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* Injection of test-specific behaviors not present in production code. |
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* Enables the simulation of indirect dependencies by letting mocks return other mocks. |
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+### |
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-=== Types of Mocks === |
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+### Types of Mocks |
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Stubs are by far the most common type of mock. Keep your tests as simple as possible. Make them more complex only when necessary. |
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-* Stubs: Simplest form, returning a hardcoded value or providing an empty method body. |
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-* Fake object: Include minimal logic to handle different case scenarios. |
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-* Spy: Injected to capture interaction data with fake objects when such data is not directly accessible. |
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-* Mock objects: Contain complex logic, simulate behaviors such as computation and exception handling, and even run tests. |
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+* **Stubs**: Simplest form, returning a hardcoded value or providing an empty method body. |
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+* **Fake object**: Include minimal logic to handle different case scenarios. |
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+* **Spy**: Records internal data of the unit being tested when such data is not directly accessible. |
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+* **Mock object**: Contains complex logic, simulates behaviors such as computation and exception handling, and can even run tests. |
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+### |
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-=== Tips === |
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+### Tips |
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-* Mock third-party libraries for unit tests to ensure proper unit functionality. Instead, use the third-party libraries in component and integration tests. |
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-* Minimize the dependencies of a unit. The fewer dependencies, the easier it is to mock and test the logic. |
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-** If a class has too many dependencies, split the class or extract two dependencies into a new class. This also results in smaller, more cohesive classes/units. |
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-** If there is more than one test class for a production class, the production class is probably too large. |
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-** If the test code is very complex and hard to understand, the production class is probably too large. |
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+* **Mock third-party libraries in unit tests** to ensure proper unit functionality. However, they should not be mocked in component and integration tests. |
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+* Aim for a **minimal number of dependencies in a unit** for easier testing and mocking: |
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+ * Limit dependencies in a unit in a similar way to the best practices for function arguments: the fewer the better, with an absolute maximum of three. |
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+ * Prefer many small classes/units to one large one for easier testing. |
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+ * If a class has excessive dependencies, consider splitting it up or extracting some dependencies into a new class to create smaller, more cohesive units. |
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+ * If a production class requires more than one test class, it's probably a sign that the class is too large. |
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+ * Overly complex test code may indicate an overly large production class. |
