Funciona para mim: IntelliJ IDEA 13.1.1, JUnit4, Java 6
Mudei o arquivo no caminho do projeto: [PROJECT_NAME] .iml
Substituído:
<library>
<CLASSES>
<root url="jar://$APPLICATION_HOME_DIR$/lib/junit-4.11.jar!/" />
</CLASSES>
<JAVADOC />
<SOURCES />
</library>
De:
<library name="JUnit4">
<CLASSES>
<root url="jar://$APPLICATION_HOME_DIR$/lib/junit-4.11.jar!/" />
<root url="jar://$APPLICATION_HOME_DIR$/lib/hamcrest-core-1.3.jar!/" />
<root url="jar://$APPLICATION_HOME_DIR$/lib/hamcrest-library-1.3.jar!/" />
</CLASSES>
<JAVADOC />
<SOURCES />
</library>
Portanto, o arquivo .iml final é:
<?xml version="1.0" encoding="UTF-8"?>
<module type="JAVA_MODULE" version="4">
<component name="NewModuleRootManager" inherit-compiler-output="true">
<exclude-output />
<content url="file://$MODULE_DIR$">
<sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
<sourceFolder url="file://$MODULE_DIR$/tests" isTestSource="true" />
</content>
<orderEntry type="inheritedJdk" />
<orderEntry type="sourceFolder" forTests="false" />
<orderEntry type="module-library">
<library name="JUnit4">
<CLASSES>
<root url="jar://$APPLICATION_HOME_DIR$/lib/junit-4.11.jar!/" />
<root url="jar://$APPLICATION_HOME_DIR$/lib/hamcrest-core-1.3.jar!/" />
<root url="jar://$APPLICATION_HOME_DIR$/lib/hamcrest-library-1.3.jar!/" />
</CLASSES>
<JAVADOC />
<SOURCES />
</library>
</orderEntry>
</component>
</module>
PS: salve o arquivo e não deixe o IntelliJ Idea recarregá-lo. Só uma vez.
junit.jar
não está relacionado ao problema