Question

So I need to test how long it takes to get the kth element from sorted arrays of varying order. I would expect the run time to be O(N), but instead it seems to be growing more like O(2^N). This indicates to me that J-Unit is timing my setup() function even though it is annotated with @Before. What am I doing wrong?

import org.junit.Before;
import org.junit.Test;

public class GetKthTest {
int[] sorted1;
BubbleSort sort = new BubbleSort();
private int k = 50;

@Before
public void setUp() {
    RandomListGen gen1 = new RandomListGen(80000);
    sorted1 = sort.sort(gen1.getArray());

}

@Test
public void hundredThous() {
    System.out.println(sorted1[k]);

}
}

Answer 1

Actually I don’t think you are doing anything wrong I think there is a bug in JUnit.

For reference I have almost the exact problem with @AfterClass JUnit @AfterClass run time is added to a poor testcase 🙁.

I have replicated your problem with generic code / JUnit4 in Eclipse.

public class GetKthTest {
int[] sorted1;
int nbr = 8000000;
private int k = 50;

@Before
public void setUp() {
    sorted1 = new int[nbr];
    Random rand = new Random();
    for (int i = 0; i < nbr; i++) {
        sorted1[i] = rand.nextInt();
    }
    Arrays.sort(sorted1);

}

@Test
public void hundredThous() {
    long start = System.currentTimeMillis();
    System.out.println(sorted1[k]);
    System.out.println("Time in ms: " + (System.currentTimeMillis() - start));
}

}

Prints

-2147455505
Time in ms: 0

,

JUnit report 1,399s