JUnit - Using Assertion


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Assertion

All the assertion are in the Assert class.

public class Assert extends java.lang.Object

This class provides a set of assertion methods useful for writing tests. Only failed assertions are recorded. Some of the important methods of Assert class are:

S.N. Methods & Description
1 void assertEquals(boolean expected, boolean actual)

Check that two primitives/Objects are equal

2 void assertTrue(boolean expected, boolean actual)

Check that a condition is true

3 void assertFalse(boolean condition)

Check that a condition is false

4 void assertNotNull(Object object)

Check that an object isn't null.

5 void assertNull(Object object)

Check that an object is null

6 void assertSame(boolean condition)

The assertSame() methods tests if two object references point to the same object

7 void assertNotSame(boolean condition)

The assertNotSame() methods tests if two object references not point to the same object

8 void assertArrayEquals(expectedArray, resultArray);

The assertArrayEquals() method will test whether two arrays are equal to each other.

Let's try to cover all of the above mentioned methods in an example. Create a java class file name TestAssertions.java in C:\ > JUNIT_WORKSPACE

import org.junit.Test;
import static org.junit.Assert.*;

public class TestAssertions {

   @Test
   public void testAssertions() {
      //test data
      String str1 = new String ("abc");
      String str2 = new String ("abc");
      String str3 = null;
      String str4 = "abc";
      String str5 = "abc";
      int val1 = 5;
      int val2 = 6;
      String[] expectedArray = {"one", "two", "three"};
      String[] resultArray =  {"one", "two", "three"};

      //Check that two objects are equal
      assertEquals(str1, str2);

      //Check that a condition is true
      assertTrue (val1 < val2);

      //Check that a condition is false
      assertFalse(val1 > val2);

      //Check that an object isn't null
      assertNotNull(str1);

      //Check that an object is null
      assertNull(str3);

      //Check if two object references point to the same object
      assertSame(str4,str5);

      //Check if two object references not point to the same object
      assertNotSame(str1,str3);

      //Check whether two arrays are equal to each other.
      assertArrayEquals(expectedArray, resultArray);
   }
}

Next, let's create a java class file name TestRunner.java in C:\ > JUNIT_WORKSPACE to execute Test case(s)

import org.junit.runner.JUnitCore;
import org.junit.runner.Result;
import org.junit.runner.notification.Failure;

public class TestRunner2 {
   public static void main(String[] args) {
      Result result = JUnitCore.runClasses(TestAssertions.class);
      for (Failure failure : result.getFailures()) {
         System.out.println(failure.toString());
      }
      System.out.println(result.wasSuccessful());
   }
} 

Compile the Test case and Test Runner classes using javac

C:\JUNIT_WORKSPACE>javac TestAssertions.java TestRunner.java

Now run the Test Runner which will run test case defined in provided Test Case class.

C:\JUNIT_WORKSPACE>java TestRunner

Verify the output.

true

Annotation

Annotations are like meta-tags that you can add to you code and apply them to methods or in class. These annotation in JUnit gives us information about test methods , which methods are going to run before & after test methods, which methods run before & after all the methods, which methods or class will be ignore during execution.

List of annotations and their meaning in JUnit :

S.N. Annotation & Description
1 @Test

The Test annotation tells JUnit that the public void method to which it is attached can be run as a test case.

2 @Before

Several tests need similar objects created before they can run. Annotating a public void method with @Before causes that method to be run before each Test method.

3 @After

If you allocate external resources in a Before method you need to release them after the test runs. Annotating a public void method with @After causes that method to be run after the Test method.

4 @BeforeClass

Annotating a public static void method with @BeforeClass causes it to be run once before any of the test methods in the class.

5 @AfterClass

This will perform the method after all tests have finished. This can be used to perform clean-up activities.

6 @Ignore

The Ignore annotation is used to ignore the test and that test will not be executed.

Create a java class file name JunitAnnotation.java in C:\ > JUNIT_WORKSPACE to test annotation

import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Ignore;
import org.junit.Test;

public class JunitAnnotation {
	
   //execute before class
   @BeforeClass
   public static void beforeClass() {
      System.out.println("in before class");
   }

   //execute after class
   @AfterClass
   public static void  afterClass() {
      System.out.println("in after class");
   }

   //execute before test
   @Before
   public void before() {
      System.out.println("in before");
   }
	
   //execute after test
   @After
   public void after() {
      System.out.println("in after");
   }
	
   //test case
   @Test
   public void test() {
      System.out.println("in test");
   }
	
   //test case ignore and will not execute
   @Ignore
   public void ignoreTest() {
      System.out.println("in ignore test");
   }
}

Next, let's create a java class file name TestRunner.java in C:\ > JUNIT_WORKSPACE to execute annotaions

import org.junit.runner.JUnitCore;
import org.junit.runner.Result;
import org.junit.runner.notification.Failure;

public class TestRunner {
   public static void main(String[] args) {
      Result result = JUnitCore.runClasses(JunitAnnotation.class);
      for (Failure failure : result.getFailures()) {
         System.out.println(failure.toString());
      }
      System.out.println(result.wasSuccessful());
   }
} 

Compile the Test case and Test Runner classes using javac

C:\JUNIT_WORKSPACE>javac JunitAnnotation.java TestRunner.java

Now run the Test Runner which will run test case defined in provided Test Case class.

C:\JUNIT_WORKSPACE>java TestRunner

Verify the output.

in before class
in before
in test
in after
in after class
true


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