Data Driven Tests in JUnit 4 with Parameterized Tests

JUnit 4 supports parameterizing a Test class to run the test methods in the class with multiple data values.

Explanation Video

Test Classes Need to be Annotated with `Parameterized.class`

@RunWith(Parameterized.class)
public class ParameterizedJunit4ExampleTest {

Create a static method to supply the data

    @Parameterized.Parameters
     public static Collection<Object[]> versionCombos() {

        List<Object[]> args = new ArrayList<>();

        // code to generate data here

        return args;
    }

this method can read from files etc,
so long as it returns a Collection of Object arrays

e.g. this method creates a list of object arrays to create a combination of data i.e. [(1,11), (1,12),…,(2,11) etc.]

    @Parameterized.Parameters
     public static Collection<Object[]> versionCombos() {

        List<Object[]> args = new ArrayList<>();

        for(int getversion=1; getversion<= 5; getversion++){
            for(int version=11; version<= 15; version++){
                args.add(new Object[]{getversion, version});
            }
        }
        return args;
    }

The `Parameters` method can have a name attribute

When tests are run they are shown as [0], [1] etc.

But it is possible to give them a dynamic name based on the data using a name attribute

@Parameterized.Parameters(
         name = "using combo getversion {0} and check version {1}")
     public static Collection<Object[]> versionCombos() {

This would display names as:

using combo getversion 1 and check version 11
using combo getversion 1 and check version 12
using combo getversion 1 and check version 13

Because the {0}, {1} are replaced with the data from the Object []

The Test Class needs a constructor

    public ParameterizedJunit4ExampleTest(
                int getversion, int checkversion){
        this.getversion = getversion;
        this.checkversion=checkversion;
    }

The arguments to the constructor should match the values in the Object[] entries.
A new class will be instantiated for all the Object[] entries in the collection
The test methods in the class will be run for each instantiation