JUnit is one of the most popular unit-testing frameworks in the Java ecosystem.
1.1. What is JUnit 5?
Unlike previous versions of JUnit, JUnit 5 is composed of several different modules from three different sub-projects.
JUnit 5 = JUnit Platform + JUnit Jupiter + JUnit Vintage
JUnit Platform - foundation layer which enables different testing frameworks to be launched on the JVM
Junit Jupiter - is the JUnit 5 test framework which is launched by the JUnit Platform
JUnit Vintage - legacy TestEngine which runs older tests
1.2. Requirements:
JUnit 5 needs already installed to run:
- at least Java 8
- Maven / Gradle (In this tutorial we'll be using Maven)
The JUnit 5 version contains a number of exciting innovations, with the goal to support new features in Java 8 and above, as well as enabling many different styles of testing.
If you want to know more about JUnit, refer to the official documentation.
2. Example project structure
.
├── pom.xml
└── src
├── main
│ ├── java
│ │ └── SourceCodeClass.java
│ └── resources
└── test
└── java
└── TestClass.java
2.1. pom.xml
There is pom.xml file, which is config file for our Java project.
According to https://maven.apache.org/guides/introduction/introduction-to-the-pom.html
A Project Object Model or POM is the fundamental unit of work in Maven. It is an XML file that contains information about the project and configuration details used by Maven to build the project. It contains default values for most projects. Examples for this is the build directory, which is
target; the source directory, which issrc/main/java; the test source directory, which issrc/test/java; and so on. When executing a task or goal, Maven looks for the POM in the current directory. It reads the POM, gets the needed configuration information, then executes the goal.Some of the configuration that can be specified in the POM are the project dependencies, the plugins or goals that can be executed, the build profiles, and so on. Other information such as the project version, description, developers, mailing lists and such can also be specified.
The simplest example of pom.xml that enables running tests in IDE and shell looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.example</groupId>
<artifactId>JUnit5_Overview<</artifactId>
<version>1.0-SNAPSHOT</version>
// This is depedency that we need to add to usew JUnit5 in our project
<dependencies>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter</artifactId>
<version>5.7.2</version>
<scope>test</scope>
</dependency>
</dependencies>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
</properties>
// This plugins enables running tests from shell
<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>3.0.0-M1</version>
</plugin>
</plugins>
</build>
</project>
2.2. main / test folders
Inside Overview/src folder you can see two subfolders:
main- here are our source codes, with working functionalities →SourceCodeClass.javatest- here are test classes, that check whether source code is working properly. This is where our JUnit5 is used →TestClass.java
3. Running tests
3.1. From shell
Remember to install Maven & Java 8!
Go to your project directory
> cd <project dir>
and then run this:
> mvn clean test // clean deletes caches
You shoud see sth like this this:
[INFO] Scanning for projects... [INFO] [INFO] -----------------------< org.example:Calculator >----------------------- [INFO] Building Calculator 1.0-SNAPSHOT [INFO] --------------------------------[ jar ]--------------------------------- [INFO] [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ Calculator --- [INFO] Deleting /home/agatafilipczak/workspace/ACH/ach-tutorials/TDD-java/Calculator/target [INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ Calculator --- [INFO] Using 'UTF-8' encoding to copy filtered resources. [INFO] skip non existing resourceDirectory /home/agatafilipczak/workspace/ACH/ach-tutorials/TDD-java/Calculator/src/main/resources [INFO] [INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ Calculator --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 1 source file to /home/agatafilipczak/workspace/ACH/ach-tutorials/TDD-java/Calculator/target/classes [INFO] [INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ Calculator --- [INFO] Using 'UTF-8' encoding to copy filtered resources. [INFO] skip non existing resourceDirectory /home/agatafilipczak/workspace/ACH/ach-tutorials/TDD-java/Calculator/src/test/resources [INFO] [INFO] --- maven-compiler-plugin:3.8.1:testCompile (default-testCompile) @ Calculator --- [INFO] Changes detected - recompiling the module! [INFO] Compiling 1 source file to /home/agatafilipczak/workspace/ACH/ach-tutorials/TDD-java/Calculator/target/test-classes [INFO] [INFO] --- maven-surefire-plugin:3.0.0-M1:test (default-test) @ Calculator --- [INFO] //This is important part, we can see that 2 tests were run, no errors and build success! [INFO] ------------------------------------------------------- [INFO] T E S T S [INFO] ------------------------------------------------------- [INFO] Running CalculatorTest [INFO] Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.041 s - in CalculatorTest [INFO] [INFO] Results: [INFO] [INFO] Tests run: 2, Failures: 0, Errors: 0, Skipped: 0 [INFO] [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 2.819 s [INFO] Finished at: 2021-10-13T19:07:48+02:00 [INFO] ------------------------------------------------------------------------
3.2. From Intellij IDE
After we have set up the code for the testing, we can run the tests and find out if the tested methods are working correctly.
- To run all tests in a test class, click
against the test class declaration and select Run. - To run an individual test, click in the gutter and select Run.
You can view test results in the Run tool window at the bottom of IDE.