Let us now have a basic example to demonstrate the step-by-step process of using JUnit.
Create a Class
Create a java class to be tested, say, MessageUtil.java in C:\>JUNIT_WORKSPACE/* * This class prints the given message on console. */ public class MessageUtil { private String message; //Constructor //@param message to be printed public MessageUtil(String message){ this.message = message; } // prints the message public String printMessage(){ System.out.println(message); return message; } }
Create Test Case Class
- Create a java test class, say, TestJunit.java.
- Add a test method testPrintMessage() to your test class.
- Add an Annotaion @Test to method testPrintMessage().
- Implement the test condition and check the condition using assertEquals API of JUnit.
import org.junit.Test; import static org.junit.Assert.assertEquals; public class TestJunit { String message = "Hello World"; MessageUtil messageUtil = new MessageUtil(message); @Test public void testPrintMessage() { assertEquals(message,messageUtil.printMessage()); } }
Create Test Runner Class
- Create a TestRunner java class.
- Use runClasses method of JUnitCore class of JUnit to run the test case of the above created test class.
- Get the result of test cases run in Result Object.
- Get failure(s) using the getFailures() method of Result object.
- Get Success result using the wasSuccessful() method of Result object.
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(TestJunit.class); for (Failure failure : result.getFailures()) { System.out.println(failure.toString()); } System.out.println(result.wasSuccessful()); } }Compile the MessageUtil, Test case and Test Runner classes using javac.
C:\JUNIT_WORKSPACE>javac MessageUtil.java TestJunit.java TestRunner.javaNow run the Test Runner, which will run the test case defined in the provided Test Case class.
C:\JUNIT_WORKSPACE>java TestRunnerVerify the output.
Hello World trueNow update TestJunit in C:\>JUNIT_WORKSPACE so that the test fails. Change the message string.
import org.junit.Test; import static org.junit.Assert.assertEquals; public class TestJunit { String message = "Hello World"; MessageUtil messageUtil = new MessageUtil(message); @Test public void testPrintMessage() { message = "New Word"; assertEquals(message,messageUtil.printMessage()); } }Let's keep the rest of the classes as is, and try to run the same Test Runner.
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(TestJunit.class); for (Failure failure : result.getFailures()) { System.out.println(failure.toString()); } System.out.println(result.wasSuccessful()); } }Now run the Test Runner, which will run the test case defined in the provided Test Case class.
C:\JUNIT_WORKSPACE>java TestRunnerVerify the output.
Hello World testPrintMessage(TestJunit): expected:<[New Wor]d> but was:<[Hello Worl]d> false
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