Part 2 – What is JUnit? How to use setup JUnit in Eclipse?

JUnit is linked as a JAR at compile-time; the framework resides under package junit.framework for JUnit 3.8 and earlier, and under package org.junit for JUnit 4 and later.

JUnit promotes the idea of “first testing then coding”, which emphasizes on setting up the test data for a piece of code that can be tested first and then implemented. This approach is like “test a little, code a little, test a little, code a little.” It increases the productivity of the programmer and the stability of the program code, which in turn reduces the stress on the programmer and the time spent on debugging.

<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.10</version>
    <scope>test</scope>
</dependency>

src/test/java – for test classes

How to execute JUnit tests?
1. Using mvn command

# Run all the unit test classes.
- mvn test

# Run a single test class.
- mvn -Dtest=TestApp1 test

# Run multiple test classes.
- mvn -Dtest=TestApp1,TestApp2 test

# Run a single test method from a test class.
- mvn -Dtest=TestApp1#testMethod1 test

# Run all test methods that match pattern 'testMethod*' from a test class.
- mvn -Dtest=TestApp1#testMethod* test

# Run all test methods match pattern 'testMethod*' and 'testMagic*' from a test class.
- mvn -Dtest=TestApp1#testMethod*+testMagic* test

2. Using Eclipse Run as > JUnit Test

Eclipse Optimize Imports to Include Static Imports

assertEquals(expectedValue, actualValue);

To use asserEquals, we should have a static import as below:

import static org.junit.Assert.assertEquals;

As a developer, it becomes very difficult to add these static imports and to avoid this and add IntelliSense to this static imports we need to configure the Eclipse.

Go to Window > Preferences > Java > Editor > Content Assist > Favorites > New Type
Then add the below imports to have a static import for JUnit.

org.hamcrest.Matchers
org.hamcrest.CoreMatchers
org.junit
org.junit.Assert
org.junit.Assume
org.junit.matchers.JUnitMatchers

By having those as favorites, if I type “assertT“ and hit Ctrl+Space, Eclipse offers up asassertThat a suggestion, and if I pick it, it will add the proper static import to the file.

Source Code
Download the source code of JUnit tutorial from below git repository :
unit-testing-and-integration-testing-with-spring-boot

Let’s go to our next tutorial where we will discuss below points :