Run as JUnit often returns "No tests found with test runner 'JUnit 4'"

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I have a simple Scala project (no external dependencies except for Scala 2.7.2.final JUnit 4.4)

source folders:

  Source/Scala           output to target/classes
  UnitTest/Source/Scala  output to target/test-classes

After creating a new test class named com/mypackage/TestMain
with JUnit 4 annotations

import org.junit.Test
import org.junit.Assert.assertTrue
@Test
class TestMain {
  @Test
  def runSamples : Unit = {
     assertTrue(true)
  }
}

the plugin compiles this file correctly
(I can see the .class file in the Navigator view of my target/test-classes folder) but I cannot run it as a JUnit test.

Eclipse shows a dialog:

No tests found with test runner 'JUnit 4'

Some discussion of this problem appeared on the mailing list;
see http://www.nabble.com/How-to-use-junit-4-with-scala-under-eclipse-3.3--td18434072.html

One workaround is to add the bin directory as a source folder.
Eclipse does not let me do this via the UI; I get an error such as

Source folder '!UnitTest/Source/Scala' in project 'sas.acl.al.scala' cannot output to distinct source folder 'target/test-classes'

I can close the project and add the directory by editing the .classpath file outside of Eclipse, and sometimes this problem goes away, but each time I add a new unit test, I have to close the project (which closes my open files) and reopen it. Even then, sometimes Eclipse loses track of the unit tests and won't run them.

I use JUnit instead of !ScalaTest, Specs etc. because our larger development process uses JUnit and Maven to build projects and run unit tests and generate reports, and also I prefer the ability to run unit tests from Eclipse and use the JUnit view.

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Imported From: https://issues.scala-lang.org/browse/SI-1590?orig=1
Reporter: @DavidBiesack
Attachments:

• window.png (created on Dec 18, 2008 6:19:56 PM UTC, 7771 bytes)

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@DavidBiesack said:
No JUnit tests found

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@DavidBiesack said:
I also get a JUnit Launch dialog "No JUnit tests found".
When I build with maven, it runs the JUnit 4 tests as expected (i.e.
via the annotations). See attached image.

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Michael Greifeneder (mikegremi) said:
I have the same problem with Eclipse 3.4.1 and Scala plugin 2.7.3 RC1. I have added @test to class and method. Class file exists, is in classpath and has annotations (checked with jclasslib byte code viewer). No luck with JUnit3 and JUnit4 runner.

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michid4 said:
This might be related:

Executing a JUnit 3 style test case (i.e. extending from class TestCase) results in "No tests found with test runner 'JUnit 3'" depending on how TestCase is imported:

//import junit.framework.TestCase  // This works
import junit.framework.{TestCase}  // this doesn't: No tests found with test runner 'JUnit 3'

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@milessabin said:
Could you check this again with the latest plugin build from trunk.

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@DavidBiesack said:
I see green :-) That is, I am now able to launch JUnit 4 tests from my Scala perspective. I've not verified this for all my Scala projects, but initial
indications are good.

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@milessabin said:
Excellent ... thanks!

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@milessabin said:
Fixed, probably at the same time as #1349.

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@DavidBiesack said:
I'm now using 2.7.6.final and this problem is occurring again. May be due to #1349, which I'm also seeing (I have JUnit 4.5 in my Build Path and am using the JUnit 4 test runner.)

This was from an old project that had JUnit 3 based tests that
I was able to run. Then today I converted to JUnit 4 using @test instead
of extends TestCase and the tests worked with annotations... for a while.
After a few edit/save/test cycles, however, the tests stopped running
and Eclipse reported the same error dialog from the JUnit view
when I clicked on the JUnit run button

No tests found with test runner 'JUnit 4'

As with #1349, I cannot invoke Run as... JUnit test from the Package Explorer view.

I did a Project -> clean and the problem persists. The tests compile
file, I just cannot run them using only the annotations.
When I switch back to extends TestCase the runner can find/execute them
without fail.

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Alex Black (alexblack) said:
I'm experiencing this problem intermittently. I'm using 2.7.7 final, and jUnit 4.7, eclipse 3.5.1.

A lot of the time it works fine, but eventually it reports it can no longer find my tests. I am attempting to invoke the tests by right clicking on the package with the test class in it, and selecting "Run As" -> "JUnit Test"

Often restarting Eclipse solves the problem.

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@milessabin said:
This was never fully functional for 2.7.x but is now really fixed on trunk.