Junit lookup from a list and assert their order

Question

Say I have a list of apple "listOfApples".

class apple {
    int serial;
    int price;
    ......
}

Multiple apple may have same serial. I have to make sure that all the apples in listOfApples are sorted based on their serial.
More precisely all apples from listOfApples that have serial 0 are in the front of the list.
How can I test listOfApples whether it keep the apple in order or not using junit ?

Have you actually tried anything? What happened? Give a [mcve]. — jonrsharpe, Mar 21 '17 at 06:44
And read about java coding conventions. Class names start upper case. And yes, your question is really missing key information. Please spend some time at the [help] to learn how things work here. Definitely not like this. — GhostCat, Mar 21 '17 at 08:33

sprinter · Answer 1 · 2017-03-21T12:42:30.143

2

This seems relatively straightforward - just test that the list is the same before and after it has been sorted:

List<Apple> sortedApples = new ArrayList<>(listOfApples);
sortedApples.sort(Comparator.comparingInt(a -> a.serial));
assertEquals(sortedApples, listOfApples);

If the two lists are equal then the original list was correctly sorted.

Addition:

Good pickup by @Harmlezz in the comments: this test could fail even though the original list is correctly sorted. An alternative is:

assertTrue(IntStream.range(1, sortedAppples.size())
    .allMatch(i -> sortedApples.get(i).serial >= sortedApples.get(i-1).serial));

edited Mar 21 '17 at 12:42

answered Mar 21 '17 at 07:11

sprinter

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This is the way to go. A `List` is equal to another `List` if it contains the same items in the same order. See https://docs.oracle.com/javase/7/docs/api/java/util/List.html#equals(java.lang.Object) – Matt Mar 21 '17 at 07:13
Thanks friend @sprinter. Seems to me it'll work. I'll check it and obviously inform you. – neelrotno Mar 21 '17 at 07:25
1

as I mentioned in my answer, apples having the same serial may appear at different positions in the list after sorting which may result in the test to fail. – Harmlezz Mar 21 '17 at 08:36
@sprinter: now I like your second solution more than mine :-) It even works for the case, when `sortedApples` is empty. – Harmlezz Mar 22 '17 at 07:12

score 1 · Answer 2 · answered Mar 21 '17 at 08:35

1

Due to the fact that apples may have the same serial, you can't rely on sorting of lists, because apples having the same serial may appear at unpredictable positions: Hence try:

@Test
public void testOrderingOfProvidedApples() {
    int serial = Integer.MIN_VALUE;
    for (Apple apple : listOfApples()) {
        assertTrue(apple.getSerial() >= serial);
        serial = apple.getSerial();
    }
}

answered Mar 21 '17 at 08:35

Harmlezz

7,972
27
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Thanks a lot @Harmlezz. It worked. – neelrotno Mar 21 '17 at 12:59

Junit lookup from a list and assert their order

2 Answers2