Junit assertNotNull example

Table of Contents

testIndia – Pass
testUSA – Fail
testBhutan – Pass

Junit 5’s org.junit.jupiter.Assertions class provides different static assertions method to write test cases.

Please note that you need to use JUnit’s org.junit.Assert class in case of JUnit 4 or JUnit 3 to assert using assertNotNull method.

Assertions.assertNotNull() checks if object is not null. In case, object is null, it will through AssertError.

public static void assertNotNull(Object actual)
public static void assertNotNull(Object actual, String message)
public static void assertNotNull(Object actual, Supplier messageSupplier)

Here is simple example


package org.arpit.java2blog;

import java.util.HashMap;
import java.util.Map;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
 
public class AssertNotNullTest {
	
	AssertNotNullTest annt;
 
    public String getCapital(String country){
        Map<String,String> countryCapitalMap = new HashMap<String,String>();
        countryCapitalMap.put("India", "Delhi");
        countryCapitalMap.put("Nepal", "Kathmandu");
        countryCapitalMap.put("China", "Beijing");
        countryCapitalMap.put("Bhutan", "Thimphu");
        return countryCapitalMap.get(country);
    }
    
    @BeforeEach
	public void beforeEachTest()
	{
    	annt = new AssertNotNullTest();
	}
    /*
     * Examples for each overloaded methods of assertNotNull
     */
    
    //public static void assertNotNull(Object actual)
    @Test
    public void testIndia(){
    	String capitalIndia=annt.getCapital("India");
    	Assertions.assertNotNull(capitalIndia);
    }
    
    //public static void assertNotNull(Object actual, String message)
    @Test
    public void testUSA(){
    	String capitalUSA=annt.getCapital("USA");
    	// You can pass message as well
    	Assertions.assertNotNull(capitalUSA,"Capital should not be null");
    }
    
    //public static void assertNotNull(Object actual, Supplier messageSupplier)
    @Test
    public void testBhutan(){
    	String capitalUSA=annt.getCapital("Bhutan");
    	// You can pass message as well
    	Assertions.assertNotNull(capitalUSA,() -> "Capital should not be null");
    }
}

package org.arpit.java2blog;

import java.util.HashMap;

import java.util.Map;

import org.junit.jupiter.api.Assertions;

import org.junit.jupiter.api.BeforeEach;

import org.junit.jupiter.api.Test;

public class AssertNotNullTest {

AssertNotNullTest annt;

public String getCapital(String country){

Map<String,String> countryCapitalMap = new HashMap<String,String>();

countryCapitalMap.put("India", "Delhi");

countryCapitalMap.put("Nepal", "Kathmandu");

countryCapitalMap.put("China", "Beijing");

countryCapitalMap.put("Bhutan", "Thimphu");

return countryCapitalMap.get(country);

}

@BeforeEach

public void beforeEachTest()

{

annt = new AssertNotNullTest();

}

* Examples for each overloaded methods of assertNotNull

//public static void assertNotNull(Object actual)

@Test

public void testIndia(){

String capitalIndia=annt.getCapital("India");

Assertions.assertNotNull(capitalIndia);

}

//public static void assertNotNull(Object actual, String message)

@Test

public void testUSA(){

String capitalUSA=annt.getCapital("USA");

// You can pass message as well

Assertions.assertNotNull(capitalUSA,"Capital should not be null");

}

//public static void assertNotNull(Object actual, Supplier messageSupplier)

@Test

public void testBhutan(){

String capitalUSA=annt.getCapital("Bhutan");

// You can pass message as well

Assertions.assertNotNull(capitalUSA,() -> "Capital should not be null");

}

When you run above testcase, you will get below output:
AssertNotNullTestOutput

Let’s understand output of each testcase:

testIndia – Pass

As countryCapitalMap contains key “India”, AssertNotNull will return true and this testcase will pass.

testUSA – Fail

As countryCapitalMap does not contain key “USA”, AssertNotNull will return true and this testcase will fail.

testBhutan – Pass

As countryCapitalMap contains key “Bhutan”, AssertNotNull will return true and this testcase will pass.

That’s all about Assertions.assertNotNull()

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