Cannot create Launcher without at least one TestEngine; consider adding an engine implementation JAR to the classpath in Junit 5

java, junit5, maven

Solution

Mixing ALPHA snapshot artifacts (i.e., `org.junit:junit5-api:5.0.0-SNAPSHOT`) with M2 artifacts (i.e., `org.junit.platform:junit-platform-surefire-provider:1.0.0-M2`), won't work.

The Maven section in the user guide suggests to check out the `pom.xml` from the junit5-maven-consumer project. If you follow that example, you will end up with something like the following.

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <java.version>1.8</java.version>
    <junit.jupiter.version>5.0.0-M2</junit.jupiter.version>
    <junit.platform.version>1.0.0-M2</junit.platform.version>
</properties>

<build>
    <plugins>
        <plugin>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.1</version>
            <configuration>
                <source>${java.version}</source>
                <target>${java.version}</target>
            </configuration>
        </plugin>
        <plugin>
            <artifactId>maven-surefire-plugin</artifactId>
            <version>2.19</version>
            <dependencies>
                <dependency>
                    <groupId>org.junit.platform</groupId>
                    <artifactId>junit-platform-surefire-provider</artifactId>
                    <version>${junit.platform.version}</version>
                </dependency>
            </dependencies>
        </plugin>
    </plugins>
</build>

<dependencies>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-api</artifactId>
        <version>${junit.jupiter.version}</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-engine</artifactId>
        <version>${junit.jupiter.version}</version>
        <scope>test</scope>
    </dependency>
</dependencies>

To write your tests, you only need the `junit-jupiter-api`; however, in order to run your tests you must have a `TestEngine` on the classpath. For JUnit Jupiter you therefore need `junit-jupiter-engine` on the classpath as well.

As Nicolai Parlog pointed out, you could add `junit-jupiter-engine` as a dependency for the `maven-surefire-plugin`; however, that would not include the `JupiterTestEngine` in the classpath for your IDE.

If you're only running tests via Maven or with a recent beta version of IntelliJ 2016 (which has built-in support for JUnit 5), then you may not care if `JupiterTestEngine` is on the classpath in your IDE. But... if you're using Eclipse, NetBeans, or a non-beta version of IntelliJ, you'll definitely want the `JupiterTestEngine` on the classpath in the IDE as well.

Regards,

Sam (core JUnit 5 committer)

Problem

Original source