How to write a Unit Test?

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  1. Define the expected and desired output for a normal case, with correct input.

  2. Now, implement the test by declaring a class, name it anything (Usually something like TestAddingModule), and add the testAdd method to it (i.e. like the one below) :

    • Write a method, and above it add the @Test annotation.
    • In the method, run your binary sum and assertEquals(expectedVal,calculatedVal).

    • Test your method by running it (in Eclipse, right click, select Run as → JUnit test). 

      //for normal addition 
@Test
public void testAdd1Plus1() 
{
    int x  = 1 ; int y = 1;
    assertEquals(2, myClass.add(x,y));
}

  3. Add other cases as desired.

    • Test that your binary sum does not throw a unexpected exception if there is an integer overflow.

    • Test that your method handles Null inputs gracefully (example below). 

      //if you are using 0 as default for null, make sure your class works in that case.
@Test
public void testAdd1Plus1() 
{
    int y = 1;
    assertEquals(0, myClass.add(null,y));
}

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