An alternative contract test style in Java

ListContract.java

package ca.jbrains.junit;

import static org.junit.Assert.assertTrue;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

import org.junit.Test;

public abstract class ListContract {
    @Test
    public void emptyList() throws Exception {
        assertTrue(createEmptyList().isEmpty());
    }

    public abstract List<Object> createEmptyList();

    public static class ArrayListRespectsListContract extends ListContract {
        @Override
        public List<Object> createEmptyList() {
            return new ArrayList<Object>();
        }
    }

    public static class LinkedListRespectsListContract extends ListContract {

        @Override
        public List<Object> createEmptyList() {
            return new LinkedList<Object>();
        }
    }
}