如何使用JUnit测试java反射代码

Question

我有一个通过反射调用方法的java类。该方法创建数据库连接并执行数据库操作。我想用JUnit测试我的反射代码。有什么办法可以做到吗？

    Class DaoImpl {

    public void setResult(String result) {
        this.result = result
    }

    public String getResult() {
        return this.result;
    }

    public void doDBoperation() {
        Connection connection = getConnection();
        Statement st = connection.createStatement();
        ResultSet rs = st.executeQuery("Select column_name from table");
        if(rs.next()) {
            result = "value";
        }
    }
}


Class ReflectionClass {

    public void invoke() {
        Class<?> noParam = {};

        Class<?> clazz = Class.forname("DaoImpl");
        Method method = clazz.getDeclaredMethod("doDBoperation", noParam);

        method.invoke(clazz.getNewInstance);
        System.out.println("This is it");
    }
}

如何为我的ReflectionClass编写JUnit测试用例？

Answer 1

正如@Ghostcat所建议的，PowerMockito可以用来模拟DAOImpl的构造函数。代码如下：

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest(ReflectionClass.class)
public class ReflectionClassTest {

  @Test
  public void invoke() throws Exception {

    DaoImpl mockedDaoImpl = PowerMockito.mock(DaoImpl.class);
    PowerMockito.whenNew(DaoImpl.class).withNoArguments().thenReturn(mockedDaoImpl);
    new ReflectionClass().invoke();
    Mockito.verify(mockedDaoImpl, Mockito.atLeastOnce()).doDBoperation();
  }
}

但是，这不起作用。当通过反射调用时，PowerMock无法模拟构造函数。