java - JUnit:当测试的类不包含方法时，类方法的测试会中断编译

Question

构建 JUnit 测试类。它被用作自动分级机。一些提交没有所有必需的类方法(即使它是规范的一部分)。 Autograder 当然只是总成绩的一部分(比如 50%)。它改进了玩 500 场游戏的问题，以测试它们是否按预期运行。

除了检查所有方法是否存在之外，最好检查它们是否也可调用。

JUnit 测试代码片段:

@Test
public void test_1p1t4_15() {
    // Test if callable
    try {
        Direction d1 = new Direction();
        checkMethod(d1.getClass(), "print");
    } catch (Exception e) {
        fail("Test fails:"+e.toString());
    }
}

checkMethod 函数有助于显示问题何时与方法的实现相关，例如可见性，例如

public void checkMethod( Class cls, String fnName) {
    // Checks method validity for methods not including an argument
    try {
        Method m = cls.getMethod(fnName);
        assertNotNull(m);        
    } catch (Exception e) {
        fail("Failed: "+e.toString());
    }
}
public void checkMethod( Class cls, String fnName, Class type) {
    // Checks method validity for methods including an argument
    try {
        Method m = cls.getMethod(fnName, type);
        assertNotNull(m);        
    } catch (Exception e) {
        fail("Failed: "+e.toString());
    }
}
public void testMethod( Class cls, String fnName) {
    // Code here
}
public void testMethod( Class cls, String fnName, argType, argValue) {
    // Code here
    // Including an argument
}

Answer 1

这是一个简单的示例，演示了如何查找和调用带参数的方法(如果该方法存在)。您需要在 JUnit 测试中调用 invokeIfExists。然后您将能够断言返回的值与您期望的值匹配。

import java.lang.reflect.*;

public class Main {

    static Object invokeIfExists(Class<?> cls, String methodName,
                                 Class<?>[] argTypes,
                                 Object callingObject, Object[] args) {
        try {
            Method method = cls.getDeclaredMethod(methodName, argTypes);
            return method.invoke(callingObject, args);
        } catch (SecurityException | NoSuchMethodException e) {
            System.err.println("Method " + methodName + " not found.");
        } catch (IllegalAccessException | IllegalArgumentException e) {
            System.err.println("Method " + methodName + " could not be invoked.");
        } catch (InvocationTargetException e) {
            System.err.println("Method " + methodName + " threw an exception.");
        }
        return null; // Or assert false, etc.
    }

    public static void main(String[] args) {
        Direction direction = new Direction("a", "b");

        // Tries to invoke "direction.print(123)"
        String printResult = (String) invokeIfExists(
            Direction.class, "print", new Class<?>[]{int.class},
            direction, new Object[]{123});
        System.out.println(printResult); // "Direction: a -> b and foo=123"

        // Tries to invoke "direction.doesntExist()"
        Object doesntExistResult = invokeIfExists(
            Direction.class, "doesntExist", new Class<?>[]{},
            direction, new Object[]{});
        System.out.println(doesntExistResult); // null
    }
}

class Direction {
    private String from, to;

    Direction(String from, String to) {
        this.from = from;
        this.to = to;
    }

    String print(int foo) {
        return "Direction: " + from + " -> " + to + " and foo=" + foo;
    }
}