Solved: unit test intellij

Testing is an integral part of development, ensuring your code performs as expected while safeguarding against bugs, regressions, and unhandled scenarios. In IntelliJ IDEA, a prominent development environment, unit testing helps us craft reliable code. The IDE offers built-in support for unit testing with frameworks such as JUnit, TestNG, and many others.

JUnit is a commonly used testing tool, effective for writing and running repeatable tests in Java. It features helpful annotations for test declarations, assertions to test expected results, assumptions that the test only continues if certain conditions are met, and test runners for running tests.

Setting up a Unit Test in IntelliJ

Firstly, to utilize unit testing in IntelliJ, we need to set up a test class.

• Create your Java class in IntelliJ to be tested.
• Right-click on the class-name or inside the class content, then click on ‘Go to’-> ‘Test’.
• In the pop-up box, specify your test name, and select the testing library (e.g., JUnit), then click ‘OK’.

public class Calculator {
    public int add(int a, int b) {
        return a + b;
    }
}

The class above, Calculator, has a method that adds two integers. Now, we go ahead to create its test class.

Writing the Test

In unit testing, each testing method should focus on a single function.

Here’s how we can write a test for the add method in the Calculator class:

import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

public class CalculatorTest {
    private Calculator calculator;

    @Before
    public void setup() {
        calculator = new Calculator();
    }

    @Test
    public void testAdd() {
        int sum = calculator.add(3, 4);
        Assert.assertEquals(7, sum);
    }
}

The ‘@Before’ annotation ensures that a fresh instance of Calculator is set up before each test. ‘testAdd()’ is the test case for the ‘add()’ method in the Calculator class. ‘assertEquals()’ is a type of assertion method in JUnit that checks if two Java ‘int’ values are equal.

Running the Test

Finally, we want to run our test to confirm the validity of our code.

To do so, simply right-click anywhere in the test class and select ‘Run’. If the circle turns green, congratulations, your test passed.


In conclusion, unit testing is an indispensable part of software development, enabling more efficient debugging, easier integration, and robust code. IntelliJ, especially when combined with JUnit, provides a convenient, efficient, and easy-to-use toolset for creating and managing our tests.

Once you start using unit tests, it will drastically improve the quality of your code as well as your confidence in it. Happy coding!