JUnit: Enable assertions in class under test

Question

I've been bit a few times by Java assert statements that didn't fail in the JUnit test suite because assertions weren't enabled in JUnit's JVM instance. To be clear, these are "black box" assertions inside implementations (checking invariants, etc) not the assertions defined by the JUnit tests themselves. Of course, I'd like to catch any such assertion failures in the test suite.

The obvious solution is to be really careful to use -enableassertions whenever I run JUnit, but I'd prefer a more robust solution. One alternative is to add the following test to every test class:

  @Test(expected=AssertionError.class)   public void testAssertionsEnabled() {     assert(false);   } 

Is there a more automatic way to accomplish this? A system-wide configuration option to JUnit? A dynamic call I could put in the setUp() method?

Answer 1

In Eclipse you can go to Windows → Preferences → Java → JUnit, which has an option to add -ea everytime a new launch configuration is created. It adds the -ea option to the Debug Configuration as well.

The full text next to a check box is

Add '-ea' to VM arguments when creating a new JUnit launch configuration

Answer 2

I propose three possible (simple?) fixes which work for me after a quick test (but you might need to check the side effects of using a static-initializer-block)

1.) Add a static-initializer block to those testcases which rely on assertions being enabled

import .... public class TestXX.... ...     static {         ClassLoader.getSystemClassLoader().setDefaultAssertionStatus(true);     }    ...    @Test(expected=AssertionError.class)    ... ... 

2.) Create a base-class which all of your test-classes extend which need assertions enabled

public class AssertionBaseTest {     static {         //static block gets inherited too         ClassLoader.getSystemClassLoader().setDefaultAssertionStatus(true);     } } 

3.) Create a test suite which runs all your test

import org.junit.runner.RunWith; import org.junit.runners.Suite;  @RunWith(Suite.class) @Suite.SuiteClasses({     //list of comma-separated classes     /*Foo.class,     Bar.class*/ }) public class AssertionTestSuite {     static {         //should run before the test classes are loaded         ClassLoader.getSystemClassLoader().setDefaultAssertionStatus(true);     }     public static void main(String args[]) {         org.junit.runner.JUnitCore.main("AssertionTestSuite");     } }