JUnit Test that ArrayList elements aren't duplicates

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Using this method that generates an ArrayList using random values from a called method getRandomInt. What would I assert to create a test method that tests that the ArrayList doesn't contain duplicates?

public static int getRandom(int min, int max) {

    return random.nextInt((max - min) + 1) + min;

public static ArrayList<Integer> getRandomIntegers(int size, int min, int max) {

    ArrayList<Integer> number = new ArrayList<Integer>();

    while (number.size() < size) {
        int random = getRandom(min, max);

        if(!number.contains(random)) {

    return number;

JUnit 4 Learning Test, Or add a test that attempts to access the fourth element in an ArrayList that only has three elements. TestArrayList.java. import static org.junit.Assert.*; import org. Simple use of JUnit to test ArrayList : Unit Test « Development Class « Java. Java; Development Class; Unit Test

You can put your elements into an Set and then compare sizes.

assert new HashSet(list).size() == list.size()

CSCI 151, You'll be constructing your very own implementation of the ArrayList data structure so that Some of the methods still aren't implemented (that is, they are abstract) and int size();: Return the number of items stored in the array, not the maximum It is simple to write a JUnit test case, especially in Eclipse:. Testing the ArrayList implementation. GitHub Gist: instantly share code, notes, and snippets.

Another approach can be to fill your ArrayList with Integers from min to max, and then call Collections.shuffle(aList).

Frequently Asked Questions, Tests can use the objects (variables) in a test fixture, with each test invoking @​Before; public void setUp() {; collection = new ArrayList<Object>();; }; @Test If defects aren't being reported and your design responds well to  In the sortDescending() method we called the overloaded Collections.sort() method to sort the elements in descending order. This version of Collections.sort() accepts the ArrayList object as the first parameter and a Comparator object that theCollections.reverseOrder() method returns as the second parameter.

You can do this to check if there are no duplicates,


where number is your arrayList. Use this

import static junit.framework.Assert.assertEquals

JUnit – How to test a List – Mkyong.com, First, exclude the JUnit bundled copy of hamcrest-core , and include the ArrayList; import java.util.Arrays assertThat; public class ListTest { @Test public void testAssertList() { List<String> actual = Arrays. @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o. Assertions are utility methods to support asserting conditions in tests; these methods are accessible through the Assert class, in JUnit 4, and the Assertions one, in JUnit 5. In order to increase the readability of the test and of the assertions itself, it's always recommended to import statically the respective class. In this way, we can refer directly to the assertion method itself without the representing class as a prefix.

[PDF] Using JUnit in Eclipse, JUnit is a Java library to help you perform unit testing. Or if you aren't using Eclipse, JUnit can example, an ArrayIntListTest might have one testing method to see whether elements can be added to the list and state things that you expect to always be true, such as assertEquals(3, list.size()); if you expect the array list. assertArrayEquals() method belongs to JUnit 4 org.junit.Assert class. In JUnit 5 all JUnit 4 assertion methods are moved to org.junit.jupiter.api.Assertions class.

Mockito basics by example – Test Driven Development, We very often use those objects in tests. When doing TDD We can ask Mockito to create a mock object for us. Then we can import org.junit.Test;. import org.​mockito.InOrder;. import org.mockito.Mockito; ArrayList arrayList = mock(​ArrayList.class); Recommended further reading: Mocks Aren't Stubs. Unit Testing. A robust set of tests is essential in helping to ensure that new changes do not negatively impact how a software system functions. One of the most popular tools for writing unit tests is the jUnit testing framework. jUnit provides an extremely simple yet powerful way to define and run tests for Java software.

Unit Testing in Java with JUnit 5, JUnit is a popular testing framework for Java. two arguments we passed are equal (see the Note below), in case they aren't - the test will fail. don't need to be of the same type (we can pass a LinkedList and an ArrayList , for example). However, their iterators must return equal elements in the same order as each other. Learn to compare two arraylists in Java with simple examples. We will first test if two arraylists are equal or not. If both lists are not equal, we will find the difference between lists. The difference in list is equals to another third list which contains either additional elements or missing elements. Also learn to find common elements

  • Why use an ArrayList. Set (HashSet) will guarantee uniqueness for you.
  • Would be rather inefficient. Exaggerated: getRandomIntegers(3, Integer.MIN_VALUE, Integer.MAX_VALUE)
  • Well, this answer isn't perfect, but for less extreme examples could be useful. I suppose in these extreme cases the THRESHOLD could be defined...
  • @M.leRutte, what about getRandomIntegers(Integer.MAX_VALUE - 1, Integer.MIN_VALUE, Integer.MAX_VALUE)?
  • This is wrong. number can contain duplicates and still its size can be same. Nit: signature is assertEquals(expected, actual)