Fundamentals of Unit Testing and TDD in .NET Quiz

Assess your foundational knowledge of unit testing concepts and test-driven development (TDD) principles in .NET applications. This quiz covers best practices, core terminology, and common patterns to help you strengthen your understanding of reliable software testing in the .NET environment.

1. Basic Understanding of Unit Tests

   Which statement best describes a unit test in the context of .NET development?

   1. A unit test is a test performed by end-users before release.
   2. A unit test verifies the functionality of a small section of code, such as a single method, in isolation.
   3. A unit test checks the performance of the entire application during heavy load.
   4. A unit test validates the visual layout of all user interfaces.

   Explanation: Unit tests are designed to check individual methods or functions to ensure they work as expected when separated from other parts. Performance and load tests are broader and focus on system-wide behavior, not small code units. Testing by end-users refers to acceptance testing. Visual layout tests do not fit the narrow scope of unit testing.

2. Purpose of Test-Driven Development

   What is the main purpose of applying Test-Driven Development (TDD) when creating .NET applications?

   1. To generate automatic user interface tests without code changes
   2. To write production code first before considering any tests
   3. To manually check the application's output after all coding is done
   4. To ensure that code meets requirements by first writing tests that define desired functionality

   Explanation: The core idea of TDD is to write tests before the code to clarify requirements and ensure every feature is tested. Writing production code before tests is the reverse of TDD. Manual checking isn't automated testing. Generating UI tests automatically is not the focus of TDD.

3. Common .NET Unit Test Attribute

   In many .NET testing frameworks, which attribute is typically used to indicate a unit test method?

   1. [TestMethod]
   2. [FactMethod]
   3. [TestIt]
   4. [UnitMethod]

   Explanation: [TestMethod] is a commonly used attribute for identifying unit tests in popular .NET testing frameworks. [UnitMethod] and [TestIt] are not standard attributes and are incorrect. [FactMethod] looks similar to [Fact], but is not a recognized attribute.

4. Behavior of TDD's 'Red-Green-Refactor'

   What is the correct sequence of the 'Red-Green-Refactor' cycle in TDD for .NET?

   1. Write refactored code, write failing test, write code to pass test
   2. Write production code, write test, refactor
   3. Write a failing test, write code to pass the test, refactor
   4. Refactor code, write test, verify test passes

   Explanation: In TDD, you first write a test that fails ('Red'), then write code to make it pass ('Green'), and finally clean up ('Refactor'). Writing refactored code first or writing production code before tests doesn't follow TDD's intended steps. The order of operations matters for test-driven approaches.

5. Characteristics of a Good Unit Test

   Which characteristic best describes a good unit test in .NET development?

   1. It should run independently and consistently, with no external dependencies.
   2. It should be dependent on the current system date and time.
   3. It is acceptable if it passes or fails unpredictably.
   4. It must require access to a live database to verify correctness.

   Explanation: A good unit test runs consistently and does not depend on external systems or unpredictable factors. Depending on current time or live databases can introduce flakiness or slow down tests. It should be reliable, and failing unpredictably is a sign of poor test quality.

6. Mock Objects Usage

   Why are mock objects commonly used in .NET unit testing?

   1. To replace application configuration files during testing
   2. To automate code formatting and style checks
   3. To directly test static helper functions
   4. To simulate and isolate dependencies, such as services or databases, from the unit under test

   Explanation: Mocks are used to imitate controlled behavior from dependencies, allowing focus on the code being tested. They don't replace configuration files, aren't for code formatting, and don't primarily target static helper testing.

7. Assertions in Unit Tests

   What is the purpose of assertions in .NET unit test methods?

   1. To specify which methods are public in a class
   2. To manage dependency injection for services
   3. To measure code coverage percentage
   4. To verify that expected outcomes match actual results during test execution

   Explanation: Assertions check if the test output matches what was expected, signifying pass or fail. Code coverage is measured separately. Method visibility isn't managed by assertions. Managing services happens outside assertions.

8. Test Naming Convention

   Which unit test name best reflects a recommended naming convention in .NET?

   1. VeryLongAndComplicatedTestNameThatDescribesEverything
   2. Test1
   3. Function_Behavior_Condition
   4. UnitTesting

   Explanation: Naming tests using the pattern 'Function_Behavior_Condition' improves clarity and understanding. 'Test1' is too generic, and 'UnitTesting' lacks context. Overly long names make tests hard to read and maintain.

9. Dependency Injection in Testing

   How does dependency injection make unit testing easier in .NET projects?

   1. By ensuring that only public fields are tested
   2. By preventing the use of private methods
   3. By tightly coupling test code to production dependencies
   4. By allowing easy replacement of dependencies with mocks or stubs

   Explanation: Dependency injection enables test code to substitute real services with mocks or stubs, isolating the code under test. It doesn't promote tight coupling, nor does it control field and method visibility. Using dependency injection increases testability and flexibility.

10. Testing for Exceptions

    In .NET unit testing, how can you verify that a method throws the expected exception?

    1. By checking the return value is null
    2. By waiting for a timeout to occur
    3. By using assertions that expect a specific exception to be thrown
    4. By inspecting private variables after method execution

    Explanation: Assertions can be written to check if a method throws the intended exception, ensuring correct error handling. Checking for a null return doesn't guarantee an exception. Timeouts are unrelated, and inspecting private variables doesn't confirm an exception was actually thrown.