Setting up JUnit with IntelliJ IDEA [duplicate]

1. Create and setup a "tests" folder
   • In the Project sidebar on the left, right-click your project and do New > Directory. Name it "test" or whatever you like.
   • Right-click the folder and choose "Mark Directory As > Test Source Root".
2. Adding JUnit library
   • Right-click your project and choose "Open Module Settings" or hit F4. (Alternatively, File > Project Structure, Ctrl-Alt-Shift-S is probably the "right" way to do this)
   • Go to the "Libraries" group, click the little green plus (look up), and choose "From Maven...".
   • Search for "junit" -- you're looking for something like "junit:junit:4.11".
   • Check whichever boxes you want (Sources, JavaDocs) then hit OK.
   • Keep hitting OK until you're back to the code.

3. Write your first unit test

   • Right-click on your test folder, "New > Java Class", call it whatever, e.g. MyFirstTest.

   • Write a JUnit test -- here's mine:

     import org.junit.Assert;
     import org.junit.Test;
     
     public class MyFirstTest {
         @Test
         public void firstTest() {
             Assert.assertTrue(true);
         }
     }
     

4. Run your tests
   • Right-click on your test folder and choose "Run 'All Tests'". Presto, testo.
   • To run again, you can either hit the green "Play"-style button that appeared in the new section that popped on the bottom of your window, or you can hit the green "Play"-style button in the top bar.

Basically, you only need junit.jar on the classpath - and here's a quick way to do it:

1. Make sure you have a source folder (e.g. test) marked as a Test Root.

2. Create a test, for example like this:

   public class MyClassTest {
       @Test
       public void testSomething() {
   
       }
   }
   

3. Since you haven't configured junit.jar (yet), the @Test annotation will be marked as an error (red), hit f2 to navigate to it.

4. Hit alt-enter and choose Add junit.jar to the classpath

There, you're done! Right-click on your test and choose Run 'MyClassTest' to run it and see the test results.

Maven Note: Altervatively, if you're using maven, at step 4 you can instead choose the option Add Maven Dependency..., go to the Search for artifact pane, type junit and take whichever version (e.g. 4.8 or 4.9).