How to write and run a JUnit test ?

Writing JUnit

• Any class can have multiple methods having test methods
• A Test method is written using annotation @Test
• Inside test method, use method Assert.assertTrue  or Assert.assertEquals to check some conditions
• It takes 2 arguments
• Label to display
• Condition to check
• You can use multiple assertTrue methods in a test method
• Here, if one condition fails, entire test will fail.

For using JUnit, put JAR junit-x.y.z.jar in classpath.
 

Example
import static org.junit.Assert.assertTrue;
import org.junit.Test;
 
public class Sample {
   public int square(int num) {
      return num * num;
   }
  
   @Test
   public void TestMyFunction() {
     Sample sample = new Sample();
     assertTrue("Check 5 ", sample.square(5) == 25);
     assertTrue("Check 7 ", sample.square(7) == 49);
     ... 
     assertEquals("Check 4 ", sample.square(4), 16);
     ...
   }

   @Test
   public void TestResult() {
     ...
     ...
   }}


Run JUnit

• In eclipse, right click on class
• Click Run as... > Run configuration... , Choose the test and Click Run
  OR
  Click Run as... > JUnit test , It runs all the tests by default.