JUnit4 Parameterized Tests (Parameterized)

The custom runner Parameterized implements parameterized tests. When running a parameterized test class, instances are created for the cross-product of the test methods and the test data elements.

For example, to test a Fibonacci function, write:

Parameterized testing is implemented in Junit4 through  Parameterized  runner.

When executing a parameterized test class, the instance's test methods and test data elements are cross-linked together when the test instance is created.

Here is the test method to test the Fibonacci number:

import static org.junit.Assert.assertEquals;

import java.util.Arrays;
import java.util.Collection;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;

@RunWith(Parameterized.class)
public class FibonacciTest {
    @Parameters
    public static Collection<Object[]> data() {
        return Arrays.asList(new Object[][] {     
                 { 0, 0 }, { 1, 1 }, { 2, 1 }, { 3, 2 }, { 4, 3 }, { 5, 5 }, { 6, 8 }  
           });
    }

    private int fInput;

    private int fExpected;

    public FibonacciTest(int input, int expected) {
        fInput= input;
        fExpected= expected;
    }

    @Test
    public void test() {
        assertEquals(fExpected, Fibonacci.compute(fInput));
    }
}

public class Fibonacci {
    public static int compute(int n) {
    	int result = 0;
    	
        if (n <= 1) {
        	result = n;
        } else {
        	result = compute(n - 1) + compute(n - 2);
        }
        
        return result;
    }
}

Each instance of the FibonacciTest class will be created with a two-argument constructor. And these two parameters will be obtained through methods annotated with @Parameters .

In addition to constructor injection, the @Parameters annotation supports property injection

import static org.junit.Assert.assertEquals;

import java.util.Arrays;
import java.util.Collection;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameter;
import org.junit.runners.Parameterized.Parameters;

@RunWith(Parameterized.class)
public class FibonacciTest {
    @Parameters
    public static Collection<Object[]> data() {
        return Arrays.asList(new Object[][] {
                 { 0, 0 }, { 1, 1 }, { 2, 1 }, { 3, 2 }, { 4, 3 }, { 5, 5 }, { 6, 8 }  
           });
    }

    @Parameter // first data value (0) is default
    public /* cannot be private */ int fInput;

    @Parameter(1)
    public /* cannot be private */ int fExpected;

    @Test
    public void test() {
        assertEquals(fExpected, Fibonacci.compute(fInput));
    }
}

public class Fibonacci {
    ...
}

Note that currently only injection of public properties is supported

single parameter test

If your test only needs a single parameter, you don't need to wrap it in an array. An iterator or array of objects can be provided in this case.

@Parameters
public static Iterable<? extends Object> data() {
    return Arrays.asList("first test", "second test");
}

or

@Parameters
public static Object[] data() {
    return new Object[] { "first test", "second test" };
}

Identify each test case

To more easily distinguish each test case in a parameterized test, you can provide a name on the @Parameters annotation.

This name can contain placeholders that will be replaced at runtime.

• {index}: the index of the current parameter
• {0}, {1}, …: The first parameter, the second parameter, etc., the parameter value. Note: single quotes  ' should be escaped into double single quotes  ''.

example

import static org.junit.Assert.assertEquals;

import java.util.Arrays;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;

@RunWith(Parameterized.class)
public class FibonacciTest {

    @Parameters(name = "{index}: fib({0})={1}")
    public static Iterable<Object[]> data() {
        return Arrays.asList(new Object[][] {
                 { 0, 0 }, { 1, 1 }, { 2, 1 }, { 3, 2 }, { 4, 3 }, { 5, 5 }, { 6, 8 }
           });
    }

    private int input;
    private int expected;

    public FibonacciTest(int input, int expected) {
        this.input = input;
        this.expected = expected;
    }

    @Test
    public void test() {
        assertEquals(expected, Fibonacci.compute(input));
    }
}

public class Fibonacci {
    ...
}

In the above example, the parameterized runner creates  names like [3: fib(3)=2]. If you don't specify a name, the index of the current parameter is used by default.

Original: https://github.com/junit-team/junit4/wiki/Parameterized-tests