CODEWITHSUNDEEP
javajunit
user2405469
user2405469

Reputation: 2003

JUnit test returning null and false

So I am practicing parameterised tests in JUnit. I created this class:

public class Operation {

    public Operation() {

    }

    public int add(int value, int num) {
        int ans = value + num;
        return ans;
    }

    public int subtract(int value, int num) {
        int ans = value - num;
        return ans;
    }
}

Nothing special, just some methods to run some tests on.

I have this test class here:

import static org.junit.Assert.*;

import java.util.Arrays;
import java.util.Collection;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;

@RunWith(Parameterized.class)
public class OperationTest {

    private int value;
    private int num;

    public OperationTest(int expected, int value, int num) {
        this.value = value;
        this.num = num;
    }

    @Parameterized.Parameters
    public static Collection primeNumbers() {
        return Arrays.asList(new Object[][] {
                { 4, 2, 2 },
                { 66, 6, 60 },
                { 20, 19, 1 },
                { 82, 22, 50 },
                { 103, 23, 80 }
        });
    }

    @Test
    public void test() {
        Operation o = new Operation();
        assertTrue(value == o.add(value, num));
    }

}

finally I have a class to run my tests:

import org.junit.runner.JUnitCore;
import org.junit.runner.Result;
import org.junit.runner.notification.Failure;

public class TestRunner {
    public static void main(String[] args) {
        Result result = JUnitCore.runClasses(OperationTest.class);
        for(Failure f : result.getFailures()) {
            System.out.println(f.toString());
        }

        System.out.println(result.wasSuccessful());
    }
}

When I run this, the output is:

test[0](OperationTest): null
test[1](OperationTest): null
test[2](OperationTest): null
test[3](OperationTest): null
test[4](OperationTest): null
false

I am expecting all of them to be true, given that { 4, 2, 2 } means expecting 4 from 2 and 2 which are given as parameters to the add method in the Operation class...I am guessing that this is probably not the right way to do it...

I would be grateful on your insight.

Upvotes: 1

Views: 5627

Answers (2)

Martijn Courteaux
Martijn Courteaux

Reputation: 68847

How can value == value + number ever be true, given that value nor number is zero (as we can see by looking at your test numbers)? You clearly missed something simple in the logic. I guess you need a third parameter that expresses the expected result, so you can do:

expected == o.add(value, number);

Upvotes: 2

Jon Skeet
Jon Skeet

Reputation: 1499860

You're not using expected anywhere - not even making it part of the state of the class. Your assertion here:

assertTrue(value == o.add(value, num));

... is not asserting what you want it to. It's only going to work when num is 0. Look at it carefully.

You should have:

// final is optional here, of course - but that's what I'd do, anyway :)
private final int expected;
private final int value;
private final int num;

public OperationTest(int expected, int value, int num) {
    this.expected = expected;
    this.value = value;
    this.num = num;
}

And then:

assertTrue(expected == o.add(value, num));

Or better (much clearer diagnostics):

assertEquals(expected, o.add(value, num));

Upvotes: 2

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