I have a maven project with a module
/myProject
pom.xml
/myModule
pom.xml
/foo
bar.txt
Consider a Junit in myModule>
Solution from @tbruyelle works if you keep your project files(.idea) in the same directory as the source code. If you choose Keep Project files in ... in a different location, then $MODULE_DIR$ is trying to look up in the workspace directory and the paths cannot be found. This looks like a bug on IntelliJ, hope they fix it soon.
Workaround: You can specify absolute / relative path of the maven module in working directory
$MODULE_DIR$/../master/mavenmodule1
$MODULE_DIR$: points to workspace directory
../: relative path to source code
master: root directory of your source code
mavenmodule1: maven module name / directory name of the child module.
For multi module maven project you don't have a choice, you need to have a different run configurations pointing to that module. I wish there is another variable that points just to the $MAVEN_MODULE$ ($MODULE_DIR$/../master/$MAVEN_MODULE$) so we can use this configuration for all modules. For the above example, $MAVEN_MODULE$ will be substituted with mavenmodule1