将值添加到Java ENUM以进行测试

Question

I'm trying to make some multi-threading test, using JMockit in a code similar to this one:

class scratch_1 {
    public static void main(String[] args) {

        for (final Car ex: Car.values()) {
            System.out.println(ex.getValue());
        }
    }
}

enum Car {
    A(1);

    public int getValue() {
        return value;
    }

    private final int value;

    Car(final int value){
        this.value = value;
    }
}

The problem is that to test this, my for cycle should handle more than one Car (the multi-threading logic happens inside). However, I can't change the enum, because at this point in time we only have 1 car, but will have more in the following springs.

How can I add another Car in runtime, only for testing?

EDIT:

This is what I have tried that didn't work:

new Car(2); -> no new instances of enumarators

Create a second class called SpecialCar with 2 SpecialCars, and replace them during tests.

Class SpecialCar extends -> enums can't be extended

mock the values() method from Car. so

new Expectations() {
            {
                 car.values();
                 result = {car.A... }

Problem : no more cars to add to array.

Answer 1

There is Car.values() . So either wait writing the unit test, or:

Add a second Car value, write a the unit tests based on values() , agnostic towards the specific constant. Remove the second Car value, and check all in into the version control system.

Some test may be disarmed because of the being just one value, and maybe even needs a check on if (Car.values().length != 0) .

Answer 2

You can have your enum implement an interface, and have a test enum that also implements that interface, and then pass the class of the appropriate enum into the test.

public interface Vehicle {
    public int getValue();
}

public enum Car implements Vehicle {
    A(1);

    public int getValue() {
        return value;
    }

    private final int value;

    Car(final int value){
        this.value = value;
    }
}

public enum TestCar implements Vehicle {
    A(1), B(2);

    public int getValue() {
        return value;
    }

    private final int value;

    Car(final int value){
        this.value = value;
    }
}

public void test(Class<? extends Vehicle> clazz) {
    for (final Vehicle vehicle : clazz.getEnumConstants()) {
        System.out.println(vehicle.getValue());
    }
}