JUnit assertEquals

Introduction to JUnit assertEquals

JUnit assertEquals is one of the methods in the JUnit Library to verify the equality of two objects. For example, one of the objects may be the program output, and the other may be externally supplied to the code. The intention of the verification is to ensure that the program works as per the desired manner during the test and take action if it is not so.

JUnit is a very powerful testing tool, in an open-source format, used for testing small as well as large blocks of code, and it has a huge collection of libraries to make testing easy and vibrant. assertEquals is one such library, and there are many more libraries under the assert family, and in this article, we will analyze them.

JUnit Assert Equals Class

assertEquals is one of the methods in the assert group that are used in test cases validation. It belongs to the org.unit.Assert class that extends java.lang.Object class. This assert class contains several methods which are useful in developing test cases to track failures.

The earlier version of JUnit, i.e., JUnit 3, had two different classes: the main class junit.framework.Testcase and an inherited class junit.framework.Assert. All the assert methods are called through the junit.framework.Assert class.

From JUnit version 4 onwards, Annotations were used to mark the tests, and there was no need to extend Testcase class which means that the assert methods are not directly available, but these methods could be imported in static mode from the new Assert class, and that is the reason all such methods under the new class are static methods.

The Assert methods can be imported using the statements

import static org.junit.Assert.*;

Post this import; these static methods can be used without prefix.

JUnit assertEquals Usage

Here the two objects are compared for equality. These objects may have integer, floating-point, and Boolean values. If the values are not equal, then AssertError will be thrown, and if the values are equal, it returns true.

assertEquals(a, b) is the exact code used in the comparison of the objects.

• The objects A and B should be of the same data type
• Objects A and B will get converted to their wrapper object type
• Value in object A will be compared with B.
• If values are equal, it will return true; otherwise, it will trigger failure.

JUnit Assert Methods

The class org.junit.Assert class contains the following methods in it, which can be called in to test various conditions.

assertArrayEquals

Method Name	Access Specifier Return Type	Details
assertArrayEquals – byte[ ]	Static void	Verifies bytes arrays (a, b) are equal
assertArrayEquals – char[ ]	Static void	Verifies char  arrays (a, b) are equal
assertArrayEquals – double[ ]	Static void	Verifies double arrays (a, b) are equal
assertArrayEquals – float[ ]	Static void	Verifies float arrays (a, b) are equal
assertArrayEquals – int[ ]	Static void	Verifies integer arrays (a, b) are equal
assertArrayEquals – long[ ]	Static void	Verifies long arrays (a, b) are equal
assertArrayEquals – objects[ ]	Static void	Verifies object arrays (a, b) are equal
assertArrayEquals – short[ ]	Static void	Verifies short arrays (a, b) are equal

The exact syntax is

assertArrayEquals ( xxxx, expecteds, xxxx, actuals )
xxxx – Byte, Char, Double, Float, Int, Long, Objects, Short
assertArrayEquals ( String, message, xxxx, expecteds, xxxx, actuals)  -  With message
xxxx – Byte, Char, Double, Float, Int, Long, Objects, Short

assertEquals

Access Specifier Return Type	Method Name / Detail of the method
static  Void	assertEquals ( double expected, double actual ) Verifies whether variables (a, b) with floating-point type are equal. This functionality is not in use. Instead of this, a new function assertEquals ( double expected, double actual, double epsilon ) is used
static void	assertEquals ( double expected, double actual, double delta ) Verifies whether variables (a, b) with floating-point type are equal within a positive delta value
static void	assertEquals ( long expected, long actual ) Verifies whether variables (a,b) with long integers type are equal
static void	assertEquals (objects [ ] expecteds, objects [] actuals ) Verifies whether multiple objects(a, b) are equal. It is not in use. Instead, it is recommended to use assertArrayEquals
static void	assertEquals (object  expected, object  actual ) Verifies whether objects (a, b) are equal.

assertEquals  (With Message)

Access Specifier Return Type	Method Name / Detail of the method
static  Void	assertEquals ( String message, double expected, double actual ) Verifies whether variables (a, b) with floating-point type are equal. This functionality is not in use. Instead of this, a new function assertEquals ( String message, double expected, double actual, double epsilon ) is used
static void	assertEquals ( String message, double expected, double actual, double delta ) Verifies whether variables (a, b) with floating-point type are equal within a positive delta value
static void	assertEquals ( String message, long expected, long actual ) Verifies whether variables (a,b) with long integers type are equal
static void	assertEquals ( String message, objects [ ] expected, objects [] actuals ) Verifies whether multiple objects(a, b) are equal. It is not in use. Instead, it is recommended to use assertArrayEquals
static void	assertEquals ( String message, object  expected, object  actual ) Verifies whether objects (a, b) are equal.

Others

Access Specifier Return Type	Method Name / Detail of the method
static void	assertFalse (boolean condition) Verifies whether the given condition is false
static void	assertFalse (String message, boolean condition) Verifies whether the given condition is false (with a message)
static void	assertNotNull(String message, Object object) Verifies whether the given object is not null
static void	assertNotsame(String message, Object unexpected Object actual) Verifies whether the two objects referred are not the same
static void	assertNull(String message, Object object) Verifies whether the given object is null
static void	assertsame(String message, Object expected Object actual) Verifies whether the two objects referred are the same
static void	assertTrue (String message, boolean condition) Verifies whether the given condition is true

Example of assertEquals

import org.junit.Test;
import static org,junit.Assert.assertEquals;    // importing assertEquals method from
//  org.junit.Assert class
String firstobject = "Jupiter";
String secondobject = "Jupiter";
assertEquals(firstobject , secondobject);

The above code will return true because both the strings have the same value.

Conclusion – JUnit assertEquals

Methods in Assert class, especially assertEquals, facilitate testing of equality conditions and ensure that an error-free product is delivered on time.

Recommended Articles

This is a guide to JUnit assertEquals. Here we discuss the following methods in it, which can be called in to test various conditions. You may also have a look at the following articles to learn more –

1. JUnit Maven Dependency
2. JUnit Annotations 
3. JUnit version
4. Java Testing Tools