Unable to Use JUnit Theories

1

My functioning Java code: 

@RunWith(Theories.class)
public class TestDoubling {
    @DataPoints
    public static int[] values() {
        return new int[] { -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
    }



  @Theory

  public void testDoubling(Integer a) {

  assertThat(doubling(a), is(a * 2));

  }


  public int doubling(int value) { return value * 2; }

}


my (hopefully) equivalent kotlin code which fails:

RunWith(javaClass<Theories>())
class Testing {
    class object {
        DataPoints
        fun values(): Array<Int> {
            return array(-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
        }
    }



  Theory

  fun testDoubling(value: Integer) {

  assertThat(doubling(value.intValue()), is(value.intValue() * 2))

  }


  fun doubling(a: Int): Int = a * 2

}


Please note that the java.lang.Integer is required- a simple int will cause the following error:

java.lang.AssertionError: Never found parameters that satisfied method assumptions.  Violated assumptions: []
     at org.junit.Assert.fail(Assert.java:88)
     at org.junit.experimental.theories.Theories$TheoryAnchor.evaluate(Theories.java:100)

That is also the exact same error message I get for the Kotlin version, even though they are- at least to my noobish eye- identical. Changing the Array<Int> to an IntArray didn't work nor removing the class object.

2

Currently you can not define a proper static method in Kotlin. We will add something to mitigate this problem in our Java interop layer. Thanks for the report.

BTW, have you tried Spek (http://blog.jetbrains.com/kotlin/2014/02/speka-specification-framework/)?

3

Logged http://youtrack.jetbrains.com/issue/KT-4861

4

You could directly annotate parameter:

RunWith(javaClass<Theories>())

class Testing {

  Theory

  fun testDoubling(TestedOn(ints = *intArray(-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9)) value: Int) {

  assertThat(doubling(value), `is`(value * 2))

  }

  fun doubling(a: Int): Int = a * 2

}

or move parameter supplier to separate class as described at https://github.com/junit-team/junit/wiki/Theories

5

Now you can use platformStatic annotation on class object functions: 

RunWith(javaClass<Theories>())
public class TestDoubling {
       class object {
           platformStatic DataPoints
               public fun values(): IntArray {
                    return intArray(-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
               }
         }



   &nbsp;&nbsp;Theory
   &nbsp;&nbsp;public fun testDoubling(a: Int?) {



                  Assert.assertThat<Int>(doubling(a!!), is<Int>(a * 2))

  }


   &nbsp;&nbsp;public fun doubling(value: Int): Int {



                  return value * 2

  }

}
6

This works for "bleeding edge" Kotlin, build 0.8.1162 and later