Using Parameterized test, one can set up a test method that retrieves data from some data source. Consider a simple test to sum different numbers. The code may look like –

The approach above leads to lot of redundancy. We need a simple approach and. Using parameterized test you can just add a method to input 10 data inputs and your test will run 10 times automatically.

Steps to create a Parameterized JUnit test

Following code shows an example for a parameterized test. It tests sum() method of the Arithmetic class : Step 1) Create a class. In this example, we are going to input two numbers by using sum (int,int) method which will return the sum of given numbers

Step 2) Create a parameterized test class

Code Explanation

Code Line 11: Annotate your test class using @runWith(Parameterized.class). Code Line 13: Declaring the variable ‘firstNumber’ as private and type as int. Code Line 14: Declaring the variable ‘secondNumber’as private and type as int. Code Line 15: Declaring the variable ‘expectedResult’as private and type as int. Code Line 16: Declaring the variable ‘airthematic’as private and type as Airthematic.

@RunWith(class_name.class): @RunWith annotation is used to specify its runner class name. If we don’t specify any type as a parameter, the runtime will choose BlockJunit4ClassRunner by default. This class is responsible for tests to run with a new test instance. It is responsible for invoking JUnit lifecycle methods such as setup(associate resources) and teardown(release resources). To parameterize you need to annotate using @RunWith and pass required .class to be tested Step 3) Create a constructor that stores the test data. It stores 3 variables

Step 4) Create a static method that generates and returns test data.

Code Line 32,33: Creating a two-dimensional array (providing input parameters for addition). Using asList method we convert the data into a List type. Since, the return type of method input is collection. Code Line 30: Using @Parameters annotation to create a set of input data to run our test. The static method identified by @Parameters annotation returns a Collection where each entry in the Collection will be the input data for one iteration of the test. Consider the elemenent {1,2,3} Here firstNumber =1 secondNumber=2 expectedResult=3 Here each array element will be passed to the constructor, one at a time as the class is instantiated multiple times. Step 5) The complete code

Code Explanation:

Code Line 25: Using @Before annotation to setup the resources (Airthematic.class here). The @Before annotation is used here to run before each test case. It contains precondition of the test. Code Line 36: Using @Test annotation to create our test. Code Line 39: Creating an assert statement to check whether our sum is equivalent to what we expected.

Step 6) Create a test runner class to run parameterized test:

Code Explanation:

Code Line 8: Declaring the main method of the class test which will run our JUnit test. Code Line 9: Executing test cases using JunitCore.runclasses, it will take the test class name as a parameter (In our example we are using Airthematic.class). Code Line 11: Processing the result using for loop and printing out failed result. Code Line 13: Printing out the successful result.

Output: Here is the output which shows successful test with no failure trace as given below:

See the result on console,which shows addition of two numbers :-

Summary: Parameterized test enables developer to execute the same test over and over again using different values. Important annotations to be used during parameterization

@RunWith @Parameters