Need to write test for a method | Smarter Dev | Page 1

true crystal Oct 1, 2023, 9:49 PM

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am basically writing test cases for this method...and it's not able to detect one of the bugs.


   // MODIFIES: this
    // EFFECTS: if there is sufficient balance on the account
    //            - subtracts amount cents from balance
    //            - adds reward points and then
    //                - if eligible, adds cash back reward(s) to account and deducts corresponding reward points
    //            - returns true
    //          otherwise, returns false
    public boolean makePurchase(int amount) {
        return false;   // stub
    }

The bug that it's not able to test is the consistency of the method if it is called multiple times. I wrote a test where this thing is called three times, but it's still not enough

hollow knot Oct 1, 2023, 9:51 PM

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Well it looks like it's missing a lot wolfshrug but it looks pretty consistent to me

true crystal Oct 1, 2023, 9:53 PM

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I have implemented the method and it works fine, but I am wondering how should I write the test to test its consistency

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public boolean makePurchase(int amount) {
        if (balance < amount) {
            return false;
        }
        balance -= amount;
        rewardPoints += amount * REWARD_POINTS_PER_CENT_CHARGED;
        if (rewardPoints >= POINTS_NEEDED_FOR_CASH_BACK) {
            balance += CASH_BACK_REWARD * (rewardPoints / POINTS_NEEDED_FOR_CASH_BACK);
            rewardPoints %= POINTS_NEEDED_FOR_CASH_BACK;
        }
        return true;
    }```

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here's the test method

📎 message.txt

hollow knot Oct 1, 2023, 9:57 PM

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Wow line 13 is.. a lot

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Anyway I'm not really sure what you mean by consistency. It should have the same affect given the same input

true crystal Oct 1, 2023, 9:59 PM

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this is basically the hint we got:

Methods should have consistent behavior, even if they are called multiple times in succession.

hollow knot Oct 1, 2023, 10:02 PM

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I think what they mean is that it won't break if you call it from the same instance twice

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So in the tests you could just define the input of the second test to the same object as the first, and the expected output as usual

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If the method modifies the object, I don't think it should return the same thing twice unless it can after the changes

true crystal Oct 1, 2023, 10:07 PM

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not sure what you mean...

hollow knot Oct 1, 2023, 10:12 PM

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So if the card only had $8 on it, calling makePurchase(500) twice would only return true the first time

true crystal Oct 1, 2023, 10:21 PM

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that didn't work

sturdy lintel Oct 2, 2023, 12:21 AM

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I took a look

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true crystal Oct 2, 2023, 12:22 AM

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bozo

sturdy lintel Oct 2, 2023, 12:26 AM

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Holy fuck, add some white space, good grief...

@Test
    void testExtraPurchasesWithDifferentValues() {
        int previousPoints = foodServiceCard11.getRewardPoints();
        int previousBalance = foodServiceCard11.getBalance();
        int firstPurchase = (POINTS_NEEDED_FOR_CASH_BACK - foodServiceCard11.getRewardPoints())/REWARD_POINTS_PER_CENT_CHARGED - 1;
        int secondPurchase = POINTS_NEEDED_FOR_CASH_BACK;
        int thirdPurchase = POINTS_NEEDED_FOR_CASH_BACK * 2;
        int balanceAfterFirstPurchase = previousBalance - firstPurchase + CASH_BACK_REWARD * ((previousPoints + firstPurchase * REWARD_POINTS_PER_CENT_CHARGED) / POINTS_NEEDED_FOR_CASH_BACK);
        int rewardAfterFirstPurchase = (previousPoints + firstPurchase * REWARD_POINTS_PER_CENT_CHARGED) % POINTS_NEEDED_FOR_CASH_BACK;
        int balanceAfterSecondPurchase = previousBalance - (firstPurchase + secondPurchase) + CASH_BACK_REWARD * (previousPoints + (firstPurchase + secondPurchase) * REWARD_POINTS_PER_CENT_CHARGED / POINTS_NEEDED_FOR_CASH_BACK);
        int rewardAfterSecondPurchase = (previousPoints + firstPurchase * REWARD_POINTS_PER_CENT_CHARGED + secondPurchase * REWARD_POINTS_PER_CENT_CHARGED) % POINTS_NEEDED_FOR_CASH_BACK;
        int balanceAfterThirdPurchase = previousBalance - (firstPurchase + secondPurchase + thirdPurchase) + CASH_BACK_REWARD * (previousPoints + (firstPurchase + secondPurchase + thirdPurchase) * REWARD_POINTS_PER_CENT_CHARGED / POINTS_NEEDED_FOR_CASH_BACK);
        int rewardAfterThirdPurchase = (previousPoints + firstPurchase * REWARD_POINTS_PER_CENT_CHARGED + secondPurchase * REWARD_POINTS_PER_CENT_CHARGED + thirdPurchase * REWARD_POINTS_PER_CENT_CHARGED) % POINTS_NEEDED_FOR_CASH_BACK;
        assertTrue(foodServiceCard11.makePurchase(firstPurchase));
        assertEquals(balanceAfterFirstPurchase, foodServiceCard11.getBalance());
        assertEquals(rewardAfterFirstPurchase, foodServiceCard11.getRewardPoints());
        assertTrue(foodServiceCard11.makePurchase(secondPurchase));
        assertEquals(balanceAfterSecondPurchase, foodServiceCard11.getBalance());
        assertEquals(rewardAfterSecondPurchase, foodServiceCard11.getRewardPoints());
        assertTrue(foodServiceCard11.makePurchase(thirdPurchase));
        assertEquals(balanceAfterThirdPurchase, foodServiceCard11.getBalance());
        assertEquals(rewardAfterThirdPurchase, foodServiceCard11.getRewardPoints());
    }```
## unreadable lol

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Ugh, forgot Discord Mobile doesn't do Java syntax highlighting

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What exactly are you trying to test with that code???

true crystal Oct 2, 2023, 12:31 AM

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true crystal this is basically the hint we got: > Methods should have consistent behavior, ev...

ignore the test lol. I just want to write a test to test this. Can't figure out a good test to test it

sturdy lintel Oct 2, 2023, 12:33 AM

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Can't you just call the same method on the same instance multiple times to check that it's consistent?

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I don't think I'd ever test that in a test... I'd have mocks to eliminate any variability so it'd be assumed consistent every run

true crystal Oct 2, 2023, 12:37 AM

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I have tested that, but it didn't catch the bug it's supposed to catch. (idk what the bug exactly is). The test is supposed to catch that bug

sturdy lintel Oct 2, 2023, 12:38 AM

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for(int i=0; i<10000000000; i++){
    Call function and assert
}

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Are they looking for an edge case? Function seems to simple for that

true crystal Oct 2, 2023, 12:45 AM

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Not sure...

sturdy lintel Oct 2, 2023, 12:46 AM

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Are you using floats at all? Maybe a rounding edge case

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Could even be the case for ints

true crystal Oct 2, 2023, 12:48 AM

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no floats

sturdy lintel Oct 2, 2023, 12:49 AM

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I'd look for edge cases in int truncations then. For example 12/4 is 3, 11/4 is 2

true crystal Oct 2, 2023, 12:49 AM

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hmm ok I will think of a way to test that

winter cliff Oct 2, 2023, 2:11 AM

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Is there a problem when rewardpoints/points needed is 2x the points needed or more?

hollow knot Oct 2, 2023, 3:30 AM

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If rewardsPoints and POINTS_NEEDED_FOR_CASH_BACK are both ints, then it'll floor the result, so it might be that

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I don't think you told us the data type of a lot of the variables here

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I'm assuming balance is an integer representing cents

true crystal Oct 2, 2023, 6:48 AM

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ok found out what the issue was

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I was testing the wrong method

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memeified_clownbehindthekeyboard

#Need to write test for a method