How can I find out if code is running inside a JUnit test or not?

It might be a good idea if you want to programmatically decide which “profile” to run. Think of Spring Profiles for configuration. Inside an integration tests you might want to test against a different database.

Here is the tested code that works

public static boolean isJUnitTest() {  
  for (StackTraceElement element : Thread.currentThread().getStackTrace()) {
    if (element.getClassName().startsWith("org.junit.")) {
      return true;
    }           
  }
  return false;
}