Maven Surefire plugin in JUnit

Introduction

The Maven Surefire plugin runs your tests automatically during the build. It helps check if your code works as expected before you finish your project.

You want to run all your JUnit tests every time you build your project.

You want to see a report showing which tests passed or failed.

You want to run tests only in certain folders or with certain names.

You want to run tests automatically on a continuous integration server.

You want to skip tests temporarily without deleting them.

Syntax

JUnit

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>3.0.0</version>
  <configuration>
    <!-- optional settings here -->
  </configuration>
</plugin>

This XML goes inside the <plugins> section of your pom.xml file.

You can add options inside <configuration> to control which tests run and how.

Examples

Basic setup to run all tests with default settings.

JUnit

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>3.0.0</version>
</plugin>

Run only test classes ending with 'Test.java'.

JUnit

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>3.0.0</version>
  <configuration>
    <includes>
      <include>**/*Test.java</include>
    </includes>
  </configuration>
</plugin>

Skip running tests during the build.

JUnit

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>3.0.0</version>
  <configuration>
    <skipTests>true</skipTests>
  </configuration>
</plugin>

Sample Program

This example shows a simple Calculator class with a test. The Maven Surefire plugin runs the test when you build with mvn test. The test checks if adding 2 and 3 equals 5.

JUnit

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

import static org.junit.jupiter.api.Assertions.assertEquals;
import org.junit.jupiter.api.Test;

public class CalculatorTest {
    @Test
    public void testAdd() {
        Calculator calc = new Calculator();
        assertEquals(5, calc.add(2, 3));
    }
}

// pom.xml snippet:
// <plugin>
//   <groupId>org.apache.maven.plugins</groupId>
//   <artifactId>maven-surefire-plugin</artifactId>
//   <version>3.0.0</version>
// </plugin>

Important Notes

Surefire automatically finds tests by default if they follow naming patterns like *Test.java or Test*.java.

You can customize which tests run by changing the <includes> and <excludes> in the configuration.

Surefire generates reports in the target/surefire-reports folder after tests run.

Summary

The Maven Surefire plugin runs your tests during the build process.

It helps catch problems early by checking your code automatically.

You configure it in your pom.xml file inside the <plugins> section.

Practice

1. What is the main purpose of the Maven Surefire plugin in a JUnit testing project?

easy

A. To deploy the application to a server

B. To compile Java source code

C. To run tests automatically during the build process

D. To package the application into a JAR file

Solution

1. Step 1: Understand the role of Maven Surefire plugin

   The Maven Surefire plugin is designed to run tests automatically during the build process, ensuring code correctness early.

2. Step 2: Differentiate from other Maven plugins

   Other plugins like compiler or deploy handle compiling or deployment, not running tests.

3. Final Answer:

   To run tests automatically during the build process -> Option C

4. Quick Check:

   Maven Surefire runs tests during build [OK]

Hint: Surefire runs tests during build, not compile or deploy [OK]

Common Mistakes:

• Confusing Surefire with compiler plugin
• Thinking Surefire packages the app
• Assuming Surefire deploys the app

2. Which XML tag correctly configures the Maven Surefire plugin in the pom.xml file?

easy

A. org.apache.maven.pluginsmaven-jar-plugin

B. org.apache.maven.pluginsmaven-compiler-plugin

C. org.junit.jupiterjunit-jupiter-engine

D. org.apache.maven.pluginsmaven-surefire-plugin

Solution

1. Step 1: Identify the correct plugin artifactId for Surefire

   The Maven Surefire plugin uses maven-surefire-plugin as its artifactId.

2. Step 2: Confirm groupId and artifactId match Surefire plugin

   The groupId is org.apache.maven.plugins, which is standard for Maven plugins.

3. Final Answer:

   <plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-surefire-plugin</artifactId></plugin> -> Option D

4. Quick Check:

   Surefire plugin artifactId = maven-surefire-plugin [OK]

Hint: Surefire plugin artifactId always contains 'surefire' [OK]

Common Mistakes:

• Using maven-compiler-plugin instead of surefire
• Confusing JUnit engine with Surefire plugin
• Using maven-jar-plugin for testing

3. Given this pom.xml snippet, what will happen when you run mvn test?

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>3.0.0-M7</version>
  <configuration>
    <includes>
      <include>**/*Test.java</include>
    </includes>
  </configuration>
</plugin>

medium

A. Only Java files ending with 'Test.java' will be run as tests

B. All Java files will be compiled but no tests will run

C. Tests will run only if file names start with 'Test'

D. No tests will run because version is invalid

Solution

1. Step 1: Understand the includes configuration

   The <includes> tag specifies which test files to run. Here, it includes files matching **/*Test.java.

2. Step 2: Interpret the pattern meaning

   The pattern means any Java file ending with 'Test.java' in any folder will be run as a test.

3. Final Answer:

   Only Java files ending with 'Test.java' will be run as tests -> Option A

4. Quick Check:

   Includes pattern '**/*Test.java' runs matching test files [OK]

Hint: Includes '**/*Test.java' runs files ending with 'Test.java' [OK]

Common Mistakes:

• Assuming all Java files run as tests
• Thinking files starting with 'Test' run
• Believing version 3.0.0-M7 is invalid

4. You added the Maven Surefire plugin to your pom.xml but tests are not running. Which of these is the most likely cause?

medium

A. The pom.xml file is not saved

B. The artifactId is misspelled as maven-surefire-plugn

C. The version tag is missing

D. JUnit tests are written in a different folder than src/test/java

Solution

1. Step 1: Check plugin artifactId spelling

   If the artifactId is misspelled, Maven cannot find the plugin, so tests won't run.

2. Step 2: Consider other causes

   Missing version usually defaults to latest, unsaved pom.xml is unlikely, and test folder location matters but less common cause.

3. Final Answer:

   The artifactId is misspelled as maven-surefire-plugn -> Option B

4. Quick Check:

   Misspelled artifactId stops Surefire plugin loading [OK]

Hint: Check artifactId spelling first if tests don't run [OK]

Common Mistakes:

• Ignoring typo in artifactId
• Assuming missing version always breaks build
• Not verifying test source folder

5. You want to run only tests tagged with @Fast annotation using Maven Surefire plugin. Which configuration snippet in pom.xml achieves this?

hard

A. Fast

B. Fast

C. **/*Fast.java

D. Fast*

Solution

1. Step 1: Understand Surefire's group filtering

   Surefire uses <groups> to include tests with specific JUnit categories or tags.

2. Step 2: Match the correct tag for including groups

   Using <groups>Fast</groups> runs only tests tagged with @Fast.

3. Final Answer:

   <configuration><groups>Fast</groups></configuration> -> Option A

4. Quick Check:

   Use <groups> to run tagged tests [OK]

Hint: Use <groups> tag to run tests with specific annotations [OK]

Common Mistakes:

• Using excludedGroups instead of groups
• Filtering by filename instead of annotation
• Using <test> tag incorrectly