Testing Output using assertEquals
Scenario1.java

public class Scenario
{	
  public int Square(int no)
  {
    return no*no;
  }
}

SquareTest.java

public class SquareTest 
{
  @Test
  public void test() 
  {
    int SquareNo = new Test1().Square(5);		
    assertEquals(25, SquareNo);
  }
}

Scenario2.java(word Counter)

public class Scenario2 
{	
 public int repeatedWords(String pWord)
 {
   int count = 0;
	
   for (int j = 0; j < pWord.length(); j++) 
   {
     if(pWord.charAt(j) == 'a')
     {
       count++;	
     }
   }	
    return count;
 }
}

RepeatTest.java

public class RepeatTest {
   @Test
   public void test() {
     Scenario2 objScenario2 = new Scenario2();		
     assertEquals(objScenario2.repeatedWords("alphabet"), 2);		
   }
}

Test suite is used to bundle a few unit test cases and run them together. In JUnit, both @RunWith and @SuiteClasses annotations are used to run the suite tests.

AllTests.java (TestSuite)

@RunWith(Suite.class)
@SuiteClasses({ RepeatTest.class, SquareTest.class })
public class AllTests {

}

Now Lets take a Real Life Scenario of Bank Account
Account.java

public class Account 
{
	public int Balance;
	
	public Account()
	{
		Balance = 0;
	}
	
	public int getAccBalance()
	{
		return Balance;
	}
	
	public void getCash(int pCash)
	{
		Balance = Balance - pCash;
	}
	
	public void putCash(int pCash)
	{
		Balance = Balance + pCash;
	}
}

BankTest.java

public class BankTest 
{
	Account objAcc = new Account();
	
	@Test
	public void checkAccBalanceTest()
	{
		assertEquals(objAcc.getAccBalance(), 0);
	}
	
	@Test
	public void checkBalAfterDepositTest()
	{
		objAcc.putCash(50);
		assertEquals(objAcc.getAccBalance(), 50);
	}
	
	@Test
	public void checkBalAfterWithdrawTest()
	{
		objAcc.getCash(30);		
		assertEquals(objAcc.getAccBalance(), 20);
	}
}

Points to Note

1. The methods in BankTest ends with Test Suffix.This ensures the test cases are executed in order.
2. The Account.java and BankTest.java are two different projects.In BankTest project the other project is added in Java Build Path