Testing is an integral part of software development as it helps detect and resolve bugs before the software is released. JUnit is a tool specifically designed for testing Java code. It helps programmers find and fix mistakes in their code by running automated tests.
JUnit is a powerful and flexible tool that is widely used for testing Java applications. It is user-friendly and has many useful features. It also works well with other popular development tools like Gradle and Maven. With JUnit, developers can create reliable tests quickly and efficiently.
That’s why when you go for an interview for a developer or programmer position, you must be aware of all the basic and advanced JUnit interview questions. Here we have curated a list of top Junit interview questions to help you prepare and get an edge during the interview.
Answer: Testing means the process of evaluating a system and its components to find whether it meets the specified requirements or not. In simple terms, testing means executing a system to identify any errors or missing gaps related to the actual requirements.
Answer: JUnit refers to the Regression Testing Framework used by developers to implement unit testing in Java, accelerate programming speed, & increase the code quality.
Answer: Unit testing means testing a single entity like a method or a class. Unit testing is a crucial part for every software company to provide a quality product to their customers.
Answer:
- Manual testing:The humans execute these test cases, so it is usually costly and time-consuming.
- Automated Testing:In this, there is no involvement of humans. The automated programs and tools execute the test cases, so it is faster and less costly than manual testing.
Answer: Following are the pros of manual testing:
- Tedious and time-consuming: As humans execute the test cases, so it is tedious and slow.
- Huge investment: As test cases are manually executed so more testers are needed in manual testing.
- Less reliable: It is less reliable as tests may not be performed precisely because of human errors.
- Non-programmable: In manual testing, no programming can be done to write sophisticated tests that fetch hidden information.
Answer: The following are the advantages of automated testing:
- The automation tests have a higher speed than other normal testing types.
- It ensures that there is less investment because the test cases are executed through automation tools. Thus, less investment in using other technical techniques.
- Automation testing is more reliable because these types of tests can perform the same kind of operations precisely. Further, every time they run; they always retain the same efficiency.
- The automation tests are programmable and can always program improved tests to depict the hidden information to the users. Therefore, they are very effective in application development.
Answer: There are four main JUnit extensions, namely JWebUnit, Cactus, XMLUnit, and MockObject; these are discussed below:
- Cactus:It is a framework that helps to test server-side Java code through implements tests inside a container. The cactus ecosystem contains two components, namely the Cactus Integration Modules and Cactus framework. The framework is an engine that offers API for writing tests, while the Cactus integration modules handle the frontend with plugins’ help.
- JWebUnit:It is a Java-based framework that provides a unified testing interface by combining the capabilities of Selenium and HtmlUnit. JWebUnit simplifies the process of navigating web applications through the table content validation, links, submission, form entry, and other features. Besides, the high-level Java API enables rapid test creation with its ready-to-use assertions.
- XMLUnit:It provides a single extension class called XMLTestCase. XMLUnit also renders supporting classes that allow assertions about the validity of an XML piece, differences between two XML pieces (Diff and DetailedDiff), the outcome of transforming XML (Transformer class), amongst others.
- MockObject:When it is impracticable or impossible to include the real objects in the unit test, mock objects can be beneficial. You can simulate the complex objects’ behavior and incorporate them with the coding steps as follows:
- Create instances of mock objects
- Set expectations and state
- Invoke code domain using mock objects as parameters
- Verify consistency
Answer: Below are the key features of JUnit:
- JUnit is an open-source framework.
- It provides Annotation to identify and pick out the test methods.
- It provides Assertions for testing expected results.
- JUnit offers test runners for running the tests.
- JUnit tests can automatically run and check their results to provide immediate feedback.
- JUnit tests can be organized and arranged into test suites containing test cases and other test suites.
- JUnit shows the test progress in the bar, i.e., green if the test is going fine and turns red if the test fails.
Answer: When the method is declared as “protected,” it can be accessed within the same package where the class is defined. Therefore, to test a “protected” method of a target class, define the test class as the target class in the same package.
Answer: The best method to test a private method is through another public method. If it cannot be done, then one of the following conditions is true:
- The private method is dead code;
- There is a design smell near a class that you’re testing.
Answer: XMLUnit provides the tools to verify an XML. It provides helpers to validate against an XML Schema, XPath queries, or XML documents against the expected outcomes. The essential part is a diff-engine that provides complete control over what kind of difference is crucial to you.
Answer: Cactus consists of two main components:
- Cactus Framework– It is the heart of Cactus, an engine that provides API to write the Cactus tests.
- Cactus IntegrationModules are frameworks and frontends that offer an easy way of using the Cactus Framework (Maven plugin, Ant scripts, Eclipse plugin).
Answer: The fixture is the set of fixed state objects utilized as a baseline for running the tests. The test fixture’s objective is to ensure a well-known and fixed environment run tests so the results can be repeated. It includes the two methods as below:
- setUp() method: It runs before each test is invoked.
- tearDown() method: It runs after each test method is invoked.
Answer: A Unit Test Case is the part of code that ensures that another part of code works as expected. To quickly obtain the desired results, a test framework is needed. JUnit is the perfect unit test framework for Java.
Answer: We can use the @Test annotation to mark a method as the test method; its results are then compared with an expected output to check if the test is successful or not.
Answer: Test suite refers to grouping some unit test cases and runs them together. In JUnit, both @Suite annotation and @RunWith are used to run the suite test.
Answer: Annotations in JUnit are meta-tags that you can add to a code. The @Test annotation marks a specific method as the test method. Some other useful annotations are @Before, @After, @BeforeClass, @AfterClass, and @Ignores. To implement a JUnit test, you need to learn the importance of these annotations. Let’s perceive some JUnit annotations:
- Test: This annotation informs JUnit that it can run a public void method as the test case. It is just a replacement for org.junit.TestCase.
- Before: If you want to execute any statements before a particular test case, you use the @Before. This annotation enables you to run similar objects before the test methods.
- Before Class: You can utilize the @BeforeClass annotation in JUnit to run the statements prior to all the test cases.
- After: This annotation causes some statements to run after each test case, like to delete reset variables, temporary files, etc.
- After Class: It lets you execute statements after all the test cases.
- Ignore: It is utilized in some statements during the execution.
Answer: Manual Testing is a kind of software testing wherein test cases are executed manually by a tester without using an automated tool. The purpose of Manual Testing is to determine the bugs, defects, and issues in the software application. Manual software testing is an important technique of all testing types that helps to find critical bugs in an application.
Answer: A well-written unit test case is the one that has an expected output and a known input computed before the test gets executed. A known input test the precondition, while an expected output tests the postcondition. It is recommended that there should be a minimum of two-unit test cases for all requirements. One amongst them should be a positive test, and another should be a negative test. If a requirement further has sub-requirements, every sub-requirement should also have two or more test cases; positive and negative.
Answer: Tests are written before the code during development to help coders write the best code. Test-driven development is an ideal way to create seamless and bug-free code. When all the tests pass, the development cycle is complete. However, when a test fails or any bug is reported, you need to write the necessary unit tests to expose the bugs and fix them. It makes it almost impossible for a particular bug to resurface later.