JUnit Assert.assertEquals() Method Example

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JUnit 4 Tutorial

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In this post, we will learn how to use the assertEquals() method with an example. 

Check out JUnit 5 tutorials and examples at JUnit 5 Tutorial

In JUnit 5, all JUnit 4 assertion methods are moved to org.junit.jupiter.api.Assertions class.

void org.junit.Assert.assertEquals(Object expected, Object actual)

This method asserts that two objects are equal. If they are not, an AssertionError without a message is thrown. If expected and actual are null, they are considered equal.

Parameters:

• expected - expected value actual - the value to check against expected

Assert.assertEquals() Method Example

Let's create a trimWhitespace() method to trim leading and trailing whitespace from the given String. We will create a JUnit test for the trimWhitespace() method to do unit testing.

import static org.junit.Assert.assertEquals;

import org.junit.Test;

public class AssertEqualsExamples {
 /**
  * Trim leading and trailing whitespace from the given {@code String}.
  * 
  * @param str
  *            the {@code String} to check
  * @return the trimmed {@code String}
  * @see java.lang.Character#isWhitespace
  */
 public static String trimWhitespace(final String str) {
     if (!(str != null && str.length() > 0)) {
           return str;
     }

     int beginIndex = 0;
     int endIndex = str.length() - 1;

     while (beginIndex <= endIndex && Character.isWhitespace(str.charAt(beginIndex))) {
          beginIndex++;
     }

     while (endIndex > beginIndex && Character.isWhitespace(str.charAt(endIndex))) {
          endIndex--;
     }

     return str.substring(beginIndex, endIndex + 1);
 }
 
 @Test
 public void testTrimWhitespace() {
     assertEquals(null, trimWhitespace(null));
     assertEquals("", trimWhitespace(""));
     assertEquals("", trimWhitespace(" "));
     assertEquals("", trimWhitespace("\t"));
     assertEquals("a", trimWhitespace(" a"));
     assertEquals("a", trimWhitespace("a "));
     assertEquals("a", trimWhitespace(" a "));
     assertEquals("a b", trimWhitespace(" a b "));
     assertEquals("a b  c", trimWhitespace(" a b  c "));
  }
}

Output:

Related JUnit Examples

• JUnit Assert.assertArrayEquals() Method Example
• JUnit Assert.assertEquals() Method Example
• JUnit Assert.assertTrue() Method Example
• JUnit Assert.assertFalse() Method Example
• JUnit Assert.assertNull() Method Example
• JUnit Assert.assertNotNull() Method Example
• JUnit Assert.assertSame() Method Example
• JUnit Assert.assertNotSame() Method Example
• JUnit Assert.fail() Method Example

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JUnit 4 Tutorial

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