How to use shuffledBy method of org.junit.runner.manipulation.Ordering class

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

Yes, by default I believe it runs tests sequentially.

JUnit 4.6 introduced an experimental ParallelRunner to run tests in parallel - I don't know of its current status. I would expect parallelism to remain an "opt-in" feature by default though. (Judging by other answers, it looks like this is now here to stay but in a slightly different form - and still opt-in.)

Keep in mind the difference between unit testing and integration testing.

Unit tests should be testing code without any outside dependencies. These dependencies are mocked using a framework like, for example, JMock.

Integration tests are important too but the major drawback of them is that they take a long time to run. You can run thousands of true unit tests in a couple of seconds, but it's not the same with integration tests.

Depending on the size of your project/development team you might want to prioritize true unit tests over integration tests. Both style of tests are important but if you are pressed for resources, just going with Unit testing may be a better idea.

I wrote an application by myself that unit tested the Web (with Spring MVC this is easy) and Service layers, as well as domain objects. But I left the DAO alone because I didn't want to write a bunch of slow integration tests. If I had more people on staff I would have gone with integration tests as well, but in this case I didn't feel the time spent would be worth it.

It depends on the JUnit version and what assert libraries you use.

• For JUnit5 and 4.13 see answer
• If you use AssertJ or google-truth, see answer

The original answer for JUnit <= 4.12 was:

    @Test(expected = IndexOutOfBoundsException.class)
    public void testIndexOutOfBoundsException() {

        ArrayList emptyList = new ArrayList();
        Object o = emptyList.get(0);

    }

Though answer has more options for JUnit <= 4.12.

Reference:

• JUnit Test-FAQ

Run in the same problem while migrating project from JAVA 8 to JAVA 11, upgrading jacoco-plugin from 0.8.1 to 0.8.4 did the job.

Analysing maven dependencies, seeing from where jacoco is pulled and then fixing the version should solve the issue.

Call Class.getConstructor() and then Constructor.newInstance() passing in the appropriate arguments. Sample code:

import java.lang.reflect.*;

public class Test {

    public Test(int x) {
        System.out.println("Constuctor called! x = " + x);
    }

    // Don't just declare "throws Exception" in real code!
    public static void main(String[] args) throws Exception {
        Class<Test> clazz = Test.class;
        Constructor<Test> ctor = clazz.getConstructor(int.class);
        Test instance = ctor.newInstance(5);           
    }
}

Coworkers of mine at our company wrote a freely available DataProvider in TestNG style for JUnit which you can find on github (https://github.com/TNG/junit-dataprovider).

We use it in very large projects and it works just fine for us. It has some advantages over JUnit's Parameterized as it will reduce the overhead of separate classes and you can execute single tests as well.

An example looks something like this

@DataProvider
public static Object[][] provideStringAndExpectedLength() {
    return new Object[][] {
        { "Hello World", 11 },
        { "Foo", 3 }
    };
}

@Test
@UseDataProvider( "provideStringAndExpectedLength" )
public void testCalculateLength( String input, int expectedLength ) {
    assertThat( calculateLength( input ) ).isEqualTo( expectedLength );
}

Edit: Since v1.7, it also supports other ways to provide data (strings, lists) and can inline the provider so that a separate method is not necessarily needed.

A full, working example can be found on the manual page on github. It also has a few more features, like collecting the providers in utility classes and accessing them from other classes etc. The manual page is very detailed, I'm sure you'll find any questions answered there.

I don't know any other solution apart from commenting out tests or renaming them. I would go for the renaming option and use my own convention. For example all of them will start with ignoreXXX(). Then you can do one find/replace with your editor and you are ready.

In order to have HSQLDB register itself, you need to access its jdbcDriver class. You can do this the same way as in this example.

Class.forName("org.hsqldb.jdbcDriver");

It triggers static initialization of jdbcDriver class, which is:

static {
    try {
        DriverManager.registerDriver(new jdbcDriver());
    } catch (Exception e) {}
}