如何对抽象类进行单元测试:使用存根进行扩展？

public abstract class AbstractCalculator {
    public abstract int calculate(int a, int b);
}

public class AdditionCalculator extends AbstractCalculator {
    @Override
    public int calculate(int a, int y) {
        return a + b;
    }
}

import static org.mockito.Mockito.*;
import static org.junit.jupiter.api.Assertions.*;
import org.junit.jupiter.api.Test;
import org.mockito.Mockito;

public class AdditionCalculatorTest {

    @Test
    public void testCalculate() {
        // 创建抽象类的存根
        AbstractCalculator stub = Mockito.mock(AbstractCalculator.class);
        when(stub.calculate(2, 3)).thenReturn(5);

        // 创建子类实例，并注入存根
        AdditionCalculator calculator = new AdditionCalculator();
        calculator.setAbstractCalculator(stub);

        // 调用被测试的方法
        int result = calculator.calculate(2, 3);

        // 验证结果
        assertEquals(5, result);
    }
}