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Saturday, January 21, 2017

JUnit - Using Assertion

Assertion

All the assertions 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 as follows −

Sr.No. Methods & Description
1 void assertEquals(boolean expected, boolean actual)
Checks that two primitives/objects are equal.
2 void assertTrue(boolean expected, boolean actual)
Checks that a condition is true.
3 void assertFalse(boolean condition)
Checks that a condition is false.
4 void assertNotNull(Object object)
Checks that an object isn't null.
5 void assertNull(Object object)
Checks that an object is null.
6 void assertSame(boolean condition)
The assertSame() method tests if two object references point to the same object.
7 void assertNotSame(boolean condition)
The assertNotSame() method tests if two object references do 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 use some of the above-mentioned methods in an example. Create a java class file named 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, create a java class file named 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 the test case defined in the provided Test Case class.
C:\JUNIT_WORKSPACE>java TestRunner
Verify the output.
true

Annotation

Annotations are like meta-tags that you can add to your code, and apply them to methods or in class. These annotations in JUnit provide the following information about test methods −
  • which methods are going to run before and after test methods.
  • which methods run before and after all the methods, and.
  • which methods or classes will be ignored during the execution.
The following table provides a list of annotations and their meaning in JUnit −
Sr.No. 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 named 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, create a java class file named TestRunner.java in C:\>JUNIT_WORKSPACE to execute annotations.
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 the test case defined in the 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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