JUnit 4 Tutorial

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

The assertTrue() method belongs to JUnit 4 org.junit.Assert class.

Check out JUnit 5 tutorials and examples at https://www.javaguides.net/p/junit-5.html

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

When to use assertTrue() method

In case we want to verify that a certain condition is true or false, we can respectively use the assertTrue assertion or the assertFalse one.

void org.junit.Assert.assertTrue(boolean condition)

Asserts that a condition is true. If it isn't it throws an AssertionError without a message.

Parameters:

condition - condition to be checked

Assert.assertTrue() method example

The below example demonstrates how to use assertTrue() method check empty or null condition methods:

import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import org.junit.Test;

public class AssertTrueExample {

 public static boolean isEmpty(final CharSequence cs) {
     return cs == null || cs.length() == 0;
 }
 
 public static boolean isBlank(final CharSequence cs) {
     int strLen;
     if (cs == null || (strLen = cs.length()) == 0) {
         return true;
     }
     for (int i = 0; i < strLen; i++) {
         if (!Character.isWhitespace(cs.charAt(i))) {
             return false;
         }
     }
     return true;
 }
 
 
 @Test
 public void isEmptyTest() {
     assertTrue(isEmpty(null));
     assertTrue(isEmpty(""));
     assertFalse(isEmpty(" "));
     assertFalse(isEmpty("bob"));
     assertFalse(isEmpty("  bob  "));
 }
 
 @Test
 public void isBlankTest() {
     assertTrue(isBlank(null));
     assertTrue(isBlank(""));
     assertTrue(isBlank(" "));
     assertFalse(isBlank("bob"));
     assertFalse(isBlank("  bob  "));
  }
}

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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