Tell intellij which java version to use for JUnit testing

Help/Discuss
1

Hi,
we have a project that needs Java 8 to run.

Now we have Java 16 around, so when importing Intellij uses Java 16 by default.

I tried to convince Intellij to use java 8 for test execution with that:

java {
        toolchain {
                languageVersion = JavaLanguageVersion.of(8)
        }
}

That works fine when using run “via Gradle”:

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However when using Run “via Intellij IDEA”, Intellij still uses Java 16:

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Is this a bug in intellij or is there some other way to steer the selection of the JDK that should be used for test execution?

You can find a full example project here: GitHub - david0/junit5-java-version

2

Perhaps you can specify a JAVA_HOME variable in the run configuration for the JDK you want? You may also be able to change your gradle JVM version if that’s an option like below.

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3

Hi Alex an thanks for your reply.

Gradle JDK has to be Java 16, since one half of the project is a Java 16 project.
The other half is legacy and has to use Java 8 :frowning:

I even set the Gradle JDK to Java 8 for one half of my project and to Java 16 for the other half.
Still intellij seems to use what is configured as Project SDK for running unit tests.

4

Of course it uses the project SDK if you don’t delegate the test execution to Gradle.
The Gradle JVM is only used - well - to execute Gradle.
That’s why “Build/Run with Gradle” and “Test with Gradle” are the defaults, because Gradle usually knows better how to do the things a project needs.
If IJ does not get the JDK right, you should open an issue with JetBrains YouTrack probably.

5

Sure, running via Gradle is always the more precise solution, unfortunately its way slower too.

I just tested again - Intellij uses does not use the Project SDK, instead it uses the “module” SDK - kind of what I expect:

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Just that this setting seems not to be synched from the gradle import. Sounds related to these tickets:

6

Once the configuration cache gets production ready, the speed difference will hopefully be neglectible. :slight_smile:

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