This page describes how we can write our first test class with JUnit 5. After we have finished this blog postpage, we:

• Can create test classes with JUnit 5.
• Know how we can use setup and teardown methods.
• Understand how we can write simple test methods with JUnit 5.

...

A basic test class looks like this:

import org.junit.jupiter.api.DisplayName;
 
@DisplayName("JUnit 5 Example")
class JUnit5ExampleTest {
     .....
}

Setup  Setup and Teardown methods

A test class can have four setup and teardown methods that must fulfill these two conditions:

• These methods must not return anything. In other words, their return type must be void.
• Setup and teardown methods cannot be private.

The supported setup and teardown methods are described in the following:

• The method that is annotated with the @BeforeAll annotation must be static, and it's run once before any test method is run.
• The method that is annotated with the @BeforeEach is invoked before each test method.
• The method that is annotated with the @AfterEach annotation is invoked after each test method.
• The method that is annotated with the @AfterAll annotation must be static, and it's run once after all test methods have been run.

Let's add these methods to our test class. After we have added these setup and teardown methods to our test class, its source looks as follows:

import org.junit.jupiter.api.*;
 
@DisplayName("JUnit 5 Example")
class JUnit5ExampleTest {
 
    @BeforeAll
    static void beforeAll() {
        System.out.println("Before all test methods");
//        Some examples of common expensive operations are:
//       - the creation of a database connection
//       - the startup of a server.     }
 
    @BeforeEach
    void beforeEach() {
        System.out.println("Before each test method");
//        This is useful when we want to execute some common code before running a test.
//        - list initialization
     }
 
    @AfterEach
    void afterEach() {
        System.out.println("After each test method");
    }
 
    @AfterAll
    static void afterAll() {
        System.out.println("After all test methods");
    }
}

...

After we have added setup and teardown methods to our test class, we can finally write our first test methods. Let's find out how we can do it.

Writing Our First Test Methods

...

A test method is a method that fulfills these three requirements:

...

Let's add two test methods to our test class:

The firstTest() method

...

and

...

 

...

secondTest() method

...

have a custom display name and

...

they write a unique string to System.out.

After we have written these two test methods, the source code of our test class looks as follows:

Code Block

import org.junit.jupiter.api.*; @DisplayName("JUnit 5 Overview Exampleclass") class JUnit5ExampleTestJUnit5OverviewTest { // Setup @BeforeAll static void beforeAll() { System.out.println("Before\nBefore all test methods \n"); // } Some examples of common expensive operations are: // - the creation of a database connection // - the startup of a server. } @BeforeEach void beforeEach() { System.out.println(" Before each test method"); // This is useful when we want to execute some common code before running a test. // - list initialization } // Teardown @AfterEach void afterEach() { System.out.println(" After each test method \n"); } @AfterAll static void afterAll() { System.out.println("After all test methods\n"); } // Added test methods @Test @DisplayName("First test") @Test void firstTest() { System.out.println(" First test method"); } @Test @DisplayName("Second test") void secondTest() { System.out.println(" Second test method"); } }

We have just written our first test methods. Let's see what happens when we run our unit tests.

Running tests

From shell

Go to your project directory 

> cd TDD-java/Overview

and then run this:

> mvn clean test

// clean deletes caches

You shoud see sth like this this:

> mvn clean test  
              
[INFO] Scanning for projects...
[INFO] 
[INFO] --------------------< org.example:JUnit5_Overview >---------------------
[INFO] Building JUnit5_Overview 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ JUnit5_Overview ---
[INFO] Deleting /home/agatafilipczak/workspace/ACH/ach-tutorials/TDD-java/Overview/target
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ JUnit5_Overview ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 0 resource
[INFO] 
[INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ JUnit5_Overview ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent!
[INFO] Compiling 1 source file to /home/agatafilipczak/workspace/ACH/ach-tutorials/TDD-java/Overview/target/classes
[INFO] 
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ JUnit5_Overview ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /home/agatafilipczak/workspace/ACH/ach-tutorials/TDD-java/Overview/src/test/resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.8.1:testCompile (default-testCompile) @ JUnit5_Overview ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent!
[INFO] Compiling 2 source files to /home/agatafilipczak/workspace/ACH/ach-tutorials/TDD-java/Overview/target/test-classes
[INFO] 
[INFO] --- maven-surefire-plugin:3.0.0-M1:test (default-test) @ JUnit5_Overview ---
[INFO] 
[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running JUnit5OverviewTest

// This is our output of tests

Before all test methods 

  Before each test method
    First test method
  After each test method 

  Before each test method
    Second test method
  After each test method 

After all test methods

// This is our results info about execution of tests

[INFO] Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.06 s - in JUnit5OverviewTest
[INFO] Running ExampleTest
example test method
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0 s - in ExampleTest
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 3, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  4.034 s
[INFO] Finished at: 2021-10-20T20:01:11+02:00
[INFO] ------------------------------------------------------------------------

From Intellij IDE

This output proves that the setup, teardown, and test methods are run in the correct order. Let's summarize what we learned from this blog post.

Summary

This tutorial has taught us

...

three things:

...

• Setup and teardown methods must not be private and they must not return anything.
• A test method is a method that isn't private and doesn't return anything.
• We could specify the display name of a test class and a test method because this allows us to replace technical names with sentences that make sense.