Setting up CI/CD on GitLab for Java projects with Maven (2021)

Environment

• GitLab (free, managed)
• JUnit 5.4
• OpenJDK 15
• Java Lang 15
• IntelliJ
• Maven 3.6

Preparing your project

Ensure you have pom.xml file ready. You can add it using IntelliJ right click on project > Add Framework Support > Maven.

Project tree

├── pom.xml
| //important - marked as test directory below in pom.xml
├── src
│   ├── HumanResourcesStatistics.java
│   ├── builders
│   │   ├── DateBuilder.java
│   │   ├── IEmployeeBuilder.java
│   │   ├── ManagerBuilder.java
│   │   ├── TraineeBuilder.java
│   │   └── WorkerBuilder.java
│   ├── model
│   │   ├── Employee.java
│   │   ├── Manager.java
│   │   ├── PayrollEntry.java
│   │   ├── Person.java
│   │   ├── Trainee.java
│   │   └── Worker.java
│   └── utils
│       ├── FakeClock.java
│       ├── IClock.java
│       └── SystemClock.java
| //important - marked as test directory below in pom.xml
└── test
    ├── Utp2Test.java
    └── Utp3Test.java

Telling Maven where sources and tests are located using pom.xml

<?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>XYZ</groupId>
    <artifactId>XYZ</artifactId>
    <version>1.0-SNAPSHOT</version>
    <build>
        <!-- important, set dir names to reflect your project directory tree as shown above -->
        <sourceDirectory>src</sourceDirectory>
        <testSourceDirectory>test</testSourceDirectory>
    </build>
    <dependencies>
        <dependency>
            <groupId>org.javatuples</groupId>
            <artifactId>javatuples</artifactId>
            <version>1.2</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
            <version>RELEASE</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
            <version>RELEASE</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <properties>
        <maven.compiler.source>15</maven.compiler.source>
        <maven.compiler.target>15</maven.compiler.target>
    </properties>

Ensuring your tests will run

In order for your tests to be run automatically, all of the following conditions must be met:

1. Tests are in a test directory marked in pom.xml
2. Test class ends with Test for example: MyServiceTest.java
3. Test class is public public class MyServiceTest { }
4. Test method is public
5. Test method is annotated with @Test attribute
6. Test method name starts with test_

For example:

//file located in PROJECT_DIR/test/MyServiceTest.java

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

public class MyServiceTest.java
{
    @Test
    public void test_task8b_get_employees_with_totalSalary_biggerThan_1k(){
        var actualEmployees = HumanResourcesStatistics.getEmployeesWithTotalSalaryBiggerThan1k(HumanResourcesStatistics.getAllEmployees());
        var expectedSize = 20;
        assertEquals(expectedSize, actualEmployees.size());
    }
}

Setting up GitLab CI/CD

Add following file named .gitlab-ci.yml to your git/project root:

variables:
  MAVEN_OPTS: '-Dhttps.protocols=TLSv1.2 -Dmaven.repo.local=$CI_PROJECT_DIR/.m2/repository -Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=WARN -Dorg.slf4j.simpleLogger.showDateTime=true -Djava.awt.headless=true'
  MAVEN_CLI_OPTS: '--batch-mode --errors --fail-at-end --show-version -DinstallAtEnd=true -DdeployAtEnd=true'

# For other maven/openjdk versions see: https://hub.docker.com/_/maven/
image: maven:3.6.3-openjdk-15
cache:
  paths:
    - .m2/repository
.verify: &verify
  stage: test
  script:
    - 'mvn $MAVEN_CLI_OPTS verify'
verify:openjdk15:
  <<: *verify

Testing Maven locally

You can use IntelliJ Maven window and run each target for example right click -> test target and see output:

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running MyServiceTest
Tests run: 6, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.068 sec

Results :

Tests run: 6, Failures: 0, Errors: 0, Skipped: 0

Result

Now commit and push your changes and on each commit you should see a GitLab pipleline starting that will compile and run unit tests.