One of the most indispensable aspects of software development in a Scrum team is unit testing. Unit testing is a crucial element to ensure that the individual pieces of the software, known as units, are working correctly. The Advanced Certified Scrum Developer (A-CSD) exam requires a good comprehension of unit-testing principles and practices, among other things. This article presents at least five unit-testing principles and practices that are crucial for success in the A-CSD exam.
First Principle: Test Independence
The objective of unit testing is to isolate each part of the software and scrutinize how it behaves on its own. As such, one crucial principle is test independence. Each test case should stand on its own, with no dependencies on other test cases. This ensures that the failure of one test case does not affect the others.
For example, if you have a test case that validates user login functionality and another one that checks user logout functionality, these two test cases should be able to execute independently. This means that the failure in the login functionality should not prevent the logout functionality from being tested.
Second Principle: Atomic Test
Closely tied to the test independence is the principle of atomic tests. An atomic test focuses on a single functional aspect.
For example, if you are testing a calculator program, you would write separate tests for addition, subtraction, multiplication, and division. This separation ensures the problem can be easily pinpointed if failure occurs.
Third Principle: Test Thoroughness
Ensuring thoroughness in testing is a key principle in unit testing. This implies that all logical paths through the unit should be tested. To achieve this, both success and failure cases need to be tested. Inputting different ranges of data including boundary values, invalid input, and valid input would be under thorough testing.
Fourth Principle: Repeatable and Consistent
Unit tests should be repeatable and produce consistent results regardless of when and how many times they are run. This makes it easier to identify when a defect was introduced into the code. For instance, a test should pass today, tomorrow, and months down the line under the same conditions.
Fifth Principle: Automated Unit Testing
Another principle encourages unit tests to be automated. This not only saves time and resources but also allows testing to be done more frequently. Automation ensures that tests are conducted regularly and consistently. Frameworks such as JUnit (for Java), NUnit (.NET), or PHPUnit (PHP), can serve this purpose.
In Conclusion
In conclusion, to excel in the A-CSD exam, understanding and applying these principles of unit testing is fundamental. Adopting these principles in your Scrum development team will enhance the overall software quality and make it easy to maintain and debug.
Practice Test
True or False: Unit Testing is a type of testing to check if the individual units of the source code are working properly.
- True
- False
Answer: True.
Explanation: A unit is the smallest testable part of any software. It usually has one or a few inputs and usually a single output.
One of the principles of Unit Testing is that each test case must be independent of the others. Is this true or false?
- True
- False
Answer: True.
Explanation: Each test case should be independent. This is to ensure that the outcome of one test does not have any impact on the others.
Indicate which of the following statements is a principle of Unit Testing:
- A. Tests should be written before the code.
- B. Tests should examine one aspect of the code at a time.
- C. Dependencies between tests should be minimized.
- D. All of the above.
Answer: D. All of the above.
Explanation: These are all important principles of unit testing. They relate to test-driven development, isolated testing, and minimizing dependencies respectively.
True or False: In Unit Testing, it is best practice to test only public methods.
- True
- False
Answer: False.
Explanation: Although testing is often done primarily on public methods, it is also important to test private methods and functions to ensure that your code is working correctly.
In Unit Testing, it is considered good practice to:
- A. Rely heavily on the debugger.
- B. Write tests for methods before they are implemented.
- C. Condense multiple assertions into a single test.
- D. Write large, complex tests.
Answer: B. Write tests for methods before they are implemented.
Explanation: Writing tests before methods are implemented is a part of test-driven development, a widely recognized best practice in software development.
True or False: Unit Tests should avoid touching the database, file system, and network.
- True
- False
Answer: True.
Explanation: Unit tests should not depend on external resources like database, file system, or network. These tests should be designed to be run in isolation.
Single select: Which of these is not a principle or best practice of unit testing?
- A. Isolate the behavior being tested.
- B. Keep tests small and focused.
- C. Use the debugger extensively to walk through code.
- D. Write a test for every bug you fix.
Answer: C. Use the debugger extensively to walk through code.
Explanation: Relying on a debugger is not a principle of unit testing since debuggers introduce their own complexities and can lead to wasted time.
True or False: Code coverage is an excellent way to find out if a line of code has been executed.
- True
- False
Answer: True.
Explanation: Code coverage reveals what proportion of your project’s code is actually being tested by unit tests, so it can help you identify which parts of your code have been executed during testing.
Multiple select: Which of the following are recommended practices for unit testing?
- A. Write self-checking tests.
- B. Test the user interface.
- C. Ensure each method is tested.
- D. Minimize debugging use.
Answer: A. Write self-checking tests, C. Ensure each method is tested, D. Minimize debugging use.
Explanation: These are all recommended practices for unit testing. While user interface (UI) testing is important too, it falls under the domain of functional or integration testing, not unit testing.
True or False: Unit Tests should be written in a separate file than the code they are testing.
- True
- False
Answer: True.
Explanation: Unit Tests are typically written in separate files or scripts to keep the source code clean and to avoid potential issues of test code interfering with production code.
Unit Tests should be written for every code path. True or false?
- True
- False
Answer: True.
Explanation: One basic rule of unit testing is that every code path should be tested to ensure that all functions perform properly in response to all possible inputs.
Unit Testing principles dictate test cases should be:
- A. Dependable and reusable.
- B. Unpredictable and dynamic.
- C. Large and complex.
- D. Based solely on a programmer’s intuition.
Answer: A. Dependable and reusable.
Explanation: Unit testing principles advise creating dependable, reusable test cases. This ensures that the same functionalities are tested consistently across different development stages.
True or False: In Unit Testing, tests should be made as complex as possible to account for all possible situations.
- True
- False
Answer: False.
Explanation: Tests should remain simple and focused. Overly complex tests can introduce their own bugs and make it unclear what exactly is being tested.
Which of these is not a practice to apply when unit testing?
- A. Refactoring the code at any time.
- B. Automating the test.
- C. Considering edge cases.
- D. Skipping testing for bugs.
Answer: D. Skipping testing for bugs.
Explanation: Unit tests should be written when bugs are detected, helping ensure the same issue doesn’t arise in the future.
True or False: Unit Tests should not depend on other tests.
- True
- False
Answer: True.
Explanation: Unit Tests are meant to be independent so their results don’t influence one another. This ensures reliable, consistent results.
Interview Questions
What is the principle of Atomicity in unit testing?
The Atomicity principle in unit testing implies that each test should be able to operate independently of others and be able to execute separately. It ensures an isolated and controlled environment for each test.
What is the concept of “Arrange-Act-Assert” in unit testing?
The “Arrange-Act-Assert” (AAA) concept in unit testing refers to a common pattern for writing test cases. First, the test data and system under test are arranged. Then action is executed on the system under test. Lastly, we assert that the expected outcomes have occurred.
Can you explain the concept of Test-Driven Development (TDD) as a practice of unit testing?
Test-Driven Development (TDD) is a software development process that relies on the repetition of a very short development cycle: first the developer writes a failing automated test case that defines a desired improvement or new function, then produces code to pass that test and finally refactors the new code to acceptable standards.
What is the principle of ‘Fast Feedback’ in unit testing?
The ‘Fast Feedback’ principle states that tests should be designed and organized in such a way that they provide quick feedback whenever any changes are made to the code, thus allowing the developer to rectify any issue as soon as it arises.
How does the principle of ‘Simplicity’ apply to unit testing?
The principle of ‘Simplicity’ implies that the unit tests should be easy to create, maintain and execute. They should be simple enough to not consume more time in writing the test than it takes to write the actual code.
Why is it important to have ‘Repeatable’ tests in unit testing?
Repeatable tests are important as they ensure that a test yields the same result every time it is executed under the same conditions. It eliminates the chance of having flaky or inconsistent results in different testing environments.
How does the principle of ‘Self-Validation’ apply to unit testing?
The principle of ‘Self-Validation’ suggests that a test should be fully automated and be able to determine by itself whether a test passes or fails, without involving any manual interpretation.
What does the unit testing practice of ‘Isolation’ mean?
The practice of ‘Isolation’ in unit testing refers to the fact that each test case should be separated from the others to prevent shared state or behavior. This also means that the unit tests run should not depend on another unit test to execute.
Can you explain the practice of ‘Test First’ in unit testing?
The ‘Test First’ practice in unit testing implies writing tests before coding. It’s a key principle of Test-Driven Development (TDD). The idea is to keep the system bug-free by fixing the bugs at the development stage itself.
What does the principle of ‘humility’ mean in the context of unit testing?
The ‘humility’ principle means accepting that anyone can make mistakes and thus should write tests to catch those mistakes. It discourages the belief of developers that their code is free from errors without testing it.
Why is it important to write ‘Maintainable’ tests in unit testing?
Maintaining tests is crucial because as the production code evolves, the test code will likewise need to change and evolve. Maintainable tests are those that can keep pace with changes to the production code without requiring too much effort.
Why is the Test-Driven Development (TDD) process also known as “Red-Green-Refactor”?
TDD process is often called “Red-Green-Refactor” because of its three steps: write a test that fails (red), write some minimum code to make the test pass (green), and then refactor both production and test code to remove duplication and improve readability.
How does the principle of ‘Readability’ apply to unit testing?
The ‘Readability’ principle requires tests to be simple and clear enough so that if the test fails, any developer can quickly understand what was expected, what actually happened, and why it failed.
Who is responsible for writing unit tests in a Scrum team?
In a Scrum team, it is generally the responsibility of the developers to write unit tests. However, everyone in the team shares the responsibility of maintaining the quality of the product, and thus, should be interested in the success of the unit tests.
Why is it recommended to use ‘mocks’ and ‘stubs’ in unit testing?
‘Mocks’ and ‘stubs’ are used in unit testing for simulating behavior of real objects. These objects are useful in testing methods in isolation, as they mimic object behaviors and usage during the testing phase without calling the real object methods.
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