Java – Run single test from a JUnit class using command-line

command linejavajunitunit testing

I am trying to find an approach that will allow me to run a single test from a JUnit class using only command-line and java.

I can run the whole set of tests from the class using the following:

java -cp .... org.junit.runner.JUnitCore org.package.classname

What I really want to do is something like this:

java -cp .... org.junit.runner.JUnitCore org.package.classname.method

or:

java -cp .... org.junit.runner.JUnitCore org.package.classname#method

I noticed that there might be ways to do this using JUnit annotations, but I would prefer to not modify the source of my test classes by hand (attempting to automate this). I did also see that Maven might have a way to do this, but if possible I would like to avoid depending on Maven.

So I am wondering if there is any way to do this?

Key points I'm looking for:

  • Ability to run a single test from a JUnit test class
  • Command Line (using JUnit)
  • Avoid modifying the test source
  • Avoid using additional tools

Best Answer

You can make a custom, barebones JUnit runner fairly easily. Here's one that will run a single test method in the form com.package.TestClass#methodName:

import org.junit.runner.JUnitCore;
import org.junit.runner.Request;
import org.junit.runner.Result;

public class SingleJUnitTestRunner {
    public static void main(String... args) throws ClassNotFoundException {
        String[] classAndMethod = args[0].split("#");
        Request request = Request.method(Class.forName(classAndMethod[0]),
                classAndMethod[1]);

        Result result = new JUnitCore().run(request);
        System.exit(result.wasSuccessful() ? 0 : 1);
    }
}

You can invoke it like this:

> java -cp path/to/testclasses:path/to/junit-4.8.2.jar SingleJUnitTestRunner 
    com.mycompany.product.MyTest#testB

After a quick look in the JUnit source I came to the same conclusion as you that JUnit does not support this natively. This has never been a problem for me since IDEs all have custom JUnit integrations that allow you to run the test method under the cursor, among other actions. I have never run JUnit tests from the command line directly; I have always let either the IDE or build tool (Ant, Maven) take care of it. Especially since the default CLI entry point (JUnitCore) doesn't produce any result output other than a non-zero exit code on test failure(s).

NOTE: for JUnit version >= 4.9 you need hamcrest library in classpath

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