Why does Intellij IDEA suddenly not recognize tests in test folder anymore?

I'm using JUnit since I started this project and everything works just fine. I have a couple of hundreds tests, and of course, here and there I start them all. Right click on root test folder, run (or debug) with JUnit. But since yesterday, when I do that, the result is:

Process finished with exit code 0

without starting any of tests. Same thing is with any folder in folder tree. I can still run a single test class, but I really need an option to start them all. If any of you have any ideas, please drop them here.

Here is what is logged when I try to run tests:

2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - IntelliJ IDEA 11.1.2  Build #IU-117.418 
2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - JDK: 1.6.0_31 
2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - VM: Java HotSpot(TM) Client VM 
2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - Vendor: Sun Microsystems Inc. 
2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - OS: Windows 7 
2012-10-31 15:16:55,693 [2727217]  ERROR - ij.psi.impl.source.PsiFileImpl - Last Action: RunClass 
2012-10-31 15:16:55,693 [2727217]  ERROR - m.intellij.util.ExecutorsQuery - com.intellij.psi.tree.IFileElementType cannot be cast to com.intellij.psi.tree.IStubFileElementType 
java.lang.ClassCastException: com.intellij.psi.tree.IFileElementType cannot be cast to com.intellij.psi.tree.IStubFileElementType
	at com.intellij.psi.impl.source.PsiFileImpl.calcStubTree(PsiFileImpl.java:976)
	at com.intellij.psi.stubs.StubIndexImpl$1.perform(StubIndexImpl.java:239)
	at com.intellij.psi.stubs.StubIndexImpl$1.perform(StubIndexImpl.java:220)
	at com.intellij.util.indexing.ValueContainer.forEach(ValueContainer.java:60)
	at com.intellij.psi.stubs.StubIndexImpl.process(StubIndexImpl.java:220)
	at com.intellij.psi.stubs.StubIndexImpl.get(StubIndexImpl.java:194)
	at com.intellij.psi.stubs.AbstractStubIndex.get(AbstractStubIndex.java:33)
	at com.intellij.psi.impl.java.stubs.index.JavaAnnotationIndex.get(JavaAnnotationIndex.java:47)
	at com.intellij.psi.impl.search.AnnotatedElementsSearcher.a(AnnotatedElementsSearcher.java:93)
	at com.intellij.psi.impl.search.AnnotatedElementsSearcher.execute(AnnotatedElementsSearcher.java:44)
	at com.intellij.psi.impl.search.AnnotatedElementsSearcher.execute(AnnotatedElementsSearcher.java:28)
	at com.intellij.util.ExecutorsQuery.processResults(ExecutorsQuery.java:42)
	at com.intellij.util.AbstractQuery.forEach(AbstractQuery.java:67)
	at com.intellij.util.InstanceofQuery.forEach(InstanceofQuery.java:54)
	at com.intellij.execution.ConfigurationUtil.addAnnotatedMethodsAnSubclasses(ConfigurationUtil.java:97)
	at com.intellij.execution.ConfigurationUtil.findAllTestClasses(ConfigurationUtil.java:77)
	at com.intellij.execution.junit.TestPackage$MySearchForTestsTask.run(TestPackage.java:397)
	at com.intellij.openapi.progress.impl.ProgressManagerImpl$TaskRunnable.run(ProgressManagerImpl.java:469)
	at com.intellij.openapi.progress.impl.ProgressManagerImpl$2.run(ProgressManagerImpl.java:178)
	at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:218)
	at com.intellij.openapi.progress.impl.ProgressManagerImpl.runProcess(ProgressManagerImpl.java:169)
	at com.intellij.openapi.progress.impl.ProgressManagerImpl$8.run(ProgressManagerImpl.java:378)
	at com.intellij.openapi.application.impl.ApplicationImpl$6.run(ApplicationImpl.java:434)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
	at java.util.concurrent.FutureTask.run(FutureTask.java:138)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:662)
	at com.intellij.openapi.application.impl.ApplicationImpl$1$1.run(ApplicationImpl.java:145)

OK, I fixed it.

In menu, under File, there is an invalidate cache option. That fixed it!

On the latest IDE (as of Community Edition 2016.1) this option is more simplified.

right click on the folder you want to be recognized as a source folder:

Mark Directory As -> Sources Root

For some reason Intellij Idea don't recognize classes as Test class that are not explicitly public, in case class has default access specificator it will not be marked as a test. Try to change class to meet this rule. Example:

public class TestMe {
   @Test
   public void shouldTest(){
      Assert.assertEquals("test", "test");
   }
}

Just to add a different scenario, which happened to me and some of my coworkers:

Alt+enter in the class -> create test: IJ (2017.1.1) proposes Arquillian Junit as first option of testing library and by going with it the test class and methods are created without the 'public' identifier. Then if one decides to change the testing library to JUnit, it is easy to forget about the absence of the 'public' identifier, which causes the tests not to be recognised by IJ. Of course, the solution is to place the 'public' identifiers.

Although this is not what happened to you it has the same consequence, therefore this answer may help others experiencing the same symptoms.

In my case, we are moving from JUnit 4 to JUnit 5 and I mixed the @Test of them.

In short:

• if you use @RunWith() of JUnit 4, you must use @org.junit.Test to annotate test methods.
• if you use @ExtendWith() of JUnit 5, you must use @org.junit.jupiter.api.Test instead.

When I change the import, my class can be run as test class again.

Fixed this a few times by... open file --> project structure. There, look on the left side menu as last entry there is "problem" count(if more then zero). click on those and then for for each problem highlighted in red in intellij in modules/libraries, remove them (minus button). They will be given module names like "test1..23" since intellij cant make out the structure. After deleting all marked red, close + restart intellij. Dont run maven refresh at this stage, since it will reintroduce the same error again. By restarting intellij will trigger a new scan of the project structure again.

None of the previous answers worked for me in IDEA 2019.1.2 (or -.3) with Junit Jupiter 5.5.0. I had git-cloned a couple of projects that I had pushed to GitHub from a different computer, where their tests ran fine. On my new laptop, I got "No tests were found" no matter how I tried to run them.

What finally did work: I deleted the IDEA-generated test.iml file, because I had noticed there was no such file in a virgin project I had created just to see if I could run tests at all (I could indeed). After I deleted this file in both older projects, tests ran perfectly. No new test.iml was generated.

I don't know how or when those files got generated. Because the git repos are private, I didn't bother to gitignore IDEA's *.*ml files; nevertheless, they weren't in the GitHub repos. Furthermore, they were at the roots of the projects, not in the .idea directory.

I ran into this issue with Ubuntu 20.04, Java 11.0.8-zulu, and Intellij 2020.2.

Upgrading Junit from 5.5.2 to 5.6.2 and Junit Platform from 1.5.2 to 1.6.2 solved it for me.

That seemed odd to me, so I switched the versions back, which now also works. I think some sort of cache invalidation is likely the best explanation, albeit the corresponding button for this didn't work for me.

So basically, what is said here https://stackoverflow.com/a/58687202/6476706 (I tried to comment there but can't...).

Anyway, still an issue in 2020, maybe this helps someone.

In my case I had to:

• close the project
• open the build.gradle file
• overwrite existing project? Yes
• right click on project
  • Mark directory as > Resources Root

Have a try changing a JUnit dependency version. One release forward or backwards. It can help invalidate test cache.

If you use a dependency management tool such as Maven or Gradle, go to the .pom or .gradle file and change the version of the JUnit library.

For instance change 4.11 to 4.12 or 4.10 in the version section:

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <!-- change here -->
      <version>4.11</version>
      <scope>test</scope>
   </dependency>
</dependencies>

I ended up manually categorising every sources root and test sources root in all the modules for the project. Worked like a charm.

If you are using IntelliJ for test execution and debugging, but not for editing. Your other editor/IDE may be battling with IntelliJ for control over generated files (*.class) -- resulting in IntelliJ reporting that No tests were found (and maybe spurious build errors too).

In my case, Visual Studio Code seem to be having this effect (after recent updates to both tools).

The solution that I have found is to close Visual Studio Code and then clean rebuild the project with IntelliJ or from the command-line. In otherwords, my dual-IDE workflow no longer works -- so I have to edit in IntelliJ.

A poor workaround for this is to let IntelliJ run tests instead of Gradle.

File > Settings > Build Tools > Gradle > Run Tests With > IntelliJ Test Runner

This is a similar issue with another test framework on Gradle. https://youtrack.jetbrains.com/issue/IDEA-221159

For me it was that the class being tested was not public. Once I set it to public the green run test icons popped up. Note, this is only an issue in Junit 4.