JUnit @Parameterized function is run before @BeforeClass in a test suite?

Question

I am using a JUnit test suite to run a few tests, one of which is run multiple times using @Parameterized. I am finding that when I run my tests, the @Parameterized function is run before @BeforeClass. Is this expected behavior or is something else happening? I would have expected that @BeforeClass would run before any of the tests are started.

Here is my test suite:

@RunWith(Suite.class)
@SuiteClasses({ Test1.class, Test2.class })
public class TestSuite {

    @BeforeClass
    public static void setup() throws Exception {
        // setup, I want this to be run before anything else
    }

}

Test1 uses @Parameterized:

public class Test1 {

    private String value;

    // @Parameterized function which appears to run before @BeforeClass setup()
    @Parameterized.Parameters
    public static Collection<Object[]> configurations() throws InterruptedException {

        // Code which relies on setup() to be run first

    }

    public Test1(String value) {
        this.value = value;
    }

    @Test
    public void testA() {
        // Test  
    }
}

How can I fix this to run the @BeforeClass setup() function before running anything else?

Answer 1

Recently ran into similar issue and solved problem using Function. Example below.

@RunWith(Parameterized.class)
public class MyClassTest {

    @Parameterized.Parameters
    public static Iterable functions() {
        return Arrays.<Object, Object>asList(
            param -> new Object()
        );
    }

    Object param;
    Function function;

    public MyClassTest(Function f) {
        this.function = f;
    }

    @Before
    public void before() {
        // construct dependency
        param = "some value";
    }

    @Test
    public void test() {
        assertThat(myClass.doSomething(function.apply(param)), is(equalTo(expectedValue)));
    }
}

In your scenario, do database setup in @Before or @BeforeClass then inject into function

Answer 2

Although beeing a bit different solution, a static block does the trick. Also note, that it must be in the Test1.class. But beside of that it works ;-)

@RunWith(Parameterized.class)
public class Test1 {

    static{
        System.out.println("Executed before everything");
    }

    private String value;

    // @Parameterized function which appears to run before @BeforeClass setup()
    @Parameterized.Parameters
    public static Collection<Object[]> configurations() throws InterruptedException {
        // Code which relies on setup() to be run first
    }

    public Test1(String value) {
        this.value = value;
    }

    @Test
    public void testA() {
        // Test  
    }
}

Answer 3

This is, unfortunately, working as intended. JUnit needs to enumerate all of the test cases before starting the test, and for parameterized tests, the method annotated with @Parameterized.Parameters is used to determine how many tests there are.