Apache Maven Maven Surefire Plugin Testing a Java class with JUnit and the Maven Surefire plugin

Example

The Maven Surefire plugin runs during the test phase of the Maven build process or when test is specified as a Maven goal. The following directory structure and minimum pom.xml file will configure Maven to run a test.

Directory structure inside the project's root directory:

─ project_root 
  ├─ pom.xml
  ├─ src
  │  ├─ main
  │  │  └─ java
  │  └─ test
  │     └─ java
  └─ target
     └─ ...

pom.xml contents:

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId>
  <artifactId>company-app</artifactId>
  <version>0.0.1</version>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>

Create a file called PlusTenTest.java with the following contents in the project's src/test/java/com/example/app directory:

package com.example.app;

import static org.junit.Assert.assertEquals;
import org.junit.Test;

public class PlusTenTest {
    
    @Test
    public void incrementTest() {
        int result = PlusTen.increment(10);
        assertEquals("PlusTen.increment(10) result", 20, result);
    }
}

The annotation @Test tells JUnit that it should run incrementTest() as a test during the test phase of the Maven build process. Now create PlusTen.java in src/main/java/com/example/app:

package com.example.app;

public class PlusTen {
    public static int increment(int value) {
        return value;
    }
}

Run the test by opening a command prompt, navigating to the project's root directory and invoking the following command:

mvn -Dtest=com.example.app.PlusTenTest test

Maven will compile the program and run the test method incrementTest() in PlusTenTest. The test will fail with the following error:

...
Tests run: 1, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.005 sec <<< FAILURE! - in com.example.app.PlusTenTest
incrementTest(com.example.app.PlusTenTest)  Time elapsed: 0.004 sec  <<< FAILURE!
java.lang.AssertionError: PlusTen.increment(10) result expected:<20> but was:<10>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at org.junit.Assert.assertEquals(Assert.java:555)
at com.example.app.PlusTenTest.incrementTest(PlusTenTest.java:12)


Results :

Failed tests:   
  PlusTenTest.incrementTest:12 PlusTen.increment(10) result expected:<20> but was:<10>

Tests run: 1, Failures: 1, Errors: 0, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.749 s
[INFO] Finished at: 2016-09-02T20:50:42-05:00
[INFO] Final Memory: 14M/209M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.19.1:test (default-test) on project app: There are test failures.
...

The Maven Surefire plugin creates a /target/surefire-reports/ directory in your project's directory containing the files com.example.app.PlusTenTest.txt and TEST-com.example.app.PlusTenTest.xml that contain the error details of the beginning of the output above.

Following the test-driven development pattern, modify PlusTen.java so that the increments() method works correctly:

package com.example.app;

public class PlusTen {
    public static int increment(int value) {
        return value + 10;
    }
}

Invoke the command again:

mvn -Dtest=com.example.app.PlusTenTest test

The test passes:

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running com.example.app.PlusTenTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.028 sec

Results :

Tests run: 1, Failures: 0, Errors: 0, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.753 s
[INFO] Finished at: 2016-09-02T20:55:42-05:00
[INFO] Final Memory: 17M/322M
[INFO] ------------------------------------------------------------------------

Congratulations! You have tested a Java class using JUnit and the Maven Surefire plugin.