Everything about JUNIT

Avinash Dogiparthi

4 min readJun 15, 2023

Junit is a unit testing framework for Java
The framework is used by Java Developers to write and execute tests
Every time a new code is added, all the test cases have to be re-executed

Unit Testing

Unit testing refers to the testing of small chunk of codes
It helps in early identification of defects
The developers are tend to spend more time on reading the code
Successful code increases the confidence of the developers

JUnit Installation

Step 1 : Require JDK

Step 2 : Any IDE ( Eclipse preferred)

Step 3 : JUnit jar files

If you’re using maven as built tool then you need to add this dependency in pom.xml file

<dependency>
  <groupId>junit</groupId>
  <artifactId>junit</artifactId>
  <version>4.13</version>
  <scope>test</scope>
</dependency>

Features of JUnit

JUnit is an open source network used to write and run tests
JUnit provides annotations to identify test methods
JUnit provides assertions to test expected results
JUnit provides test runners to run the tests
JUnit allows faster code writing, that increases the code’s quality
The tests in JUnit are automatically run, that provide instant feedback

JUnit Annotations

JUnit Annotations refers to the syntactic meta-data added to the Java source code for better structure and readability.
The biggest difference between JUnit 3 & JUnit4 is the introduction of JUnit Annotations.

Frequently used JUnit Annotations

@Test : Tells JUnit which public void method can be run as a test case.

@Before : To execute some statement before each test case.

@After : To execute some statement after each test case.

@Ignores : Used to ignore some statements during test execution.

@BeforeClass : Used to execute a statement before all the test cases

@AfterClass : Used to execute a statement after all the test cases.

@Test (timeout = 500) : Used to set some timeout while executing the test.

@Test (expected=illegalArgumentException.class) : Used to handle some exception during the test execution.

@BeforeEach : The setUp() method annotated with @BeforeEach is a setup method in JUnit 5. This method is executed before each test method in the test class.

Parameterized Test

Parameterized tests allow a developer to run the same test over and over again using different values

Output :

JUnit Testing in JAVA

Mockito

What is Mocking?

Mocking refers to the development of objects which are a mock or clone of real objects.
In the technique mock objects are used instead of real objects for testing.
Mock objects give a particular output for each particular input.
Mockito is the most popular framework used for mocking.

What is Mockito?

Mockito is a Java based framework used for unit testing of Java applications
This mocking framework helps in development of testable applications
Java Reflection API is used internally to generate mock objects
Mockito is used to simplify the test development by mocking external dependencies and using them in the code

When to use Mockito?

When a component is to be tested, but that component depends on some other component, which is under development.
When the real component perform slowly, then mock objects are used to perform testing.
When there are any concerns with the infrastructure that makes the testing impossible

What is a Stub?

Stubs are objects holding predefined data and uses the data to give responses during the tests
It can be refereed to as an object that looks like a real object with least number of methods
Stubs return the pre-defined outputs no matter what the input is
These stubs are used to reduce complexities that occur while creating the real objects