测试 ClassNotFound 异常

Question

我正在尝试使用 Android 上的 UnitTest 测试未找到 class。

发生了什么：
1. 我正在编写一个 android 库，其中包含 transitive 依赖项，这些依赖项在主机应用程序中解析
2. 开发者可以删除一些依赖，例如 remove all com.example.package
3. 我有一个工厂，它将尝试实例化（使用反射）一个对象并捕获 ClassNotFoundException。如果开发者去掉依赖，应该会抛出异常。
4. 我想测试这个案例，但我发现的只是依赖性问题，而不是如何测试它。

我要测试的示例代码

try {
    sNetworkResponseBuilderClass = OkHttpNetworkResponse.Builder.class;
} catch (Exception e){
    // <<<< I want to test this case
    new ClassNotFoundException("Unable to find OkHttpNetworkResponse.Builder.class").printStackTrace();
    return null;
}

使用的库： hamcrast、mockito、JUnit 4。

你知道怎么做吗？

Answer 1

不太确定我是否正确理解了你的问题，但你可以检查 JUnit 是否抛出异常：

@Test(expected=ClassNotFoundException.class)
public void testClassNotFoundException() {
    // a case where the exception gets thrown
}

Answer 2

在 catch 中，您可以使用 instanceof 运算符检查对象：

try {
    sNetworkResponseBuilderClass = OkHttpNetworkResponse.Builder.class;
} catch (Exception e){
    if(e instanceof ClassNotFoundException){
        // here you can do the code you want in case of ClassNotFoundException thrown
    }
}

Answer 3

这是你的字典问题。在你的字典中 test class 不会有 .换字典。

Answer 4

所以对我来说，您需要做的第一件事是提取可以抛出 ClassNotFoundException 的代码部分，以便能够轻松地模拟它，例如：

public Class<? extends NetworkResponseBuilder> getNetworkResponseBuilderClass()
    throws ClassNotFoundException {
    // Your logic here
}

然后您可以使用 Mockito.spy 测试一个真实的工厂实例，以便能够重新定义方法 getNetworkResponseBuilderClass() 的行为，如下所示：

public void testFactoryIfNetworkResponseBuilderNotFound() {
    Factory factory = spy(new Factory());
    when(factory.getNetworkResponseBuilderClass()).thenThrow(
        new ClassNotFoundException()
    );
    // The rest of your test here
}

public void testFactoryIfNetworkResponseBuilderFound() {
    Factory factory = spy(new Factory());
    when(factory.getNetworkResponseBuilderClass()).thenReturn(
        OkHttpNetworkResponse.Builder.class
    );
    // The rest of your test here
}

有关 Mockito.spy 的更多详细信息。

Answer 5

很简单的问题。下面以JUnit4异常单元测试为例。希望它会澄清你。

MyNumber.java

public class MyNumber {
   int number;
   public MyNumber div(MyNumber rhs) {
      if (rhs.number == 0) throw new IllegalArgumentException("Cannot divide by 0!");
      this.number /= rhs.number;
      return this;
   }
}

MyNumberTest.java

public class MyNumberTest {
   private MyNumber number1, number2; // Test fixtures
   @Test(expected = IllegalArgumentException.class)
   public void testDivByZero() {
      System.out.println("Run @Test testDivByZero"); // for illustration
      number2.setNumber(0);
      number1.div(number2);
   }
}

JUnit - 异常测试

要测试代码是否抛出所需的异常，请使用注释 @Test(expected = exception.class)，如上例所示。对于您的情况，它将是

/**
* Check for class not found exception
**/
@Test(expected=ClassNotFoundException.class)
public void testClassNotFoundException() {
    .....
}

For better understanding, you can go through this tutorial: Java Unit Testing - JUnit & TestNG. It contains full running code example step by step with explanation.

Answer 6

使用Class.forName("com.example.ClassName")

try {
 Class.forName("com.example.OkHttpNetworkResponse.Builder");
} catch (ClassNotFoundException e) {
  // This class was not found
}

见Class.forName(String className)

Answer 7

OkHttpNetworkResponse.Builder可能如下：

package com.example.model;

public class OkHttpNetworkResponse {
    public static class Builder {

    }
}

I have a Factory that will try to instantiate (using reflection) an Object and catch the ClassNotFoundException. If the developer remove the dependencies, the exception should be thrown.

Factory Class: 将创建任何对象可能如下所示：

package com.example.factory;

public class Factory {
    public static Object getInstance(String className)
            throws ClassNotFoundException, InstantiationException,
            IllegalAccessException {
        Class clazz = Class.forName(className);
        return clazz.newInstance();
    }
}

The developer may remove some dependencies for example remove all com.example.package

I want to test this case, but all I found is issue with dependencies, not how to test for it.

FactoryTest Class: 将测试是否抛出 ClassNotFoundException 可能如下所示： N.B: 请检查慎重评论。

package com.example.factory;

import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import java.io.File;
import java.io.IOException;

import org.junit.Test;

public class FactoryTest {
    Factory factory;

    @Test(expected=ClassNotFoundException.class)
    public void test() throws IOException, ClassNotFoundException, InstantiationException, IllegalAccessException {
        ClassLoader loader = FactoryTest.class.getClassLoader();
        String directory = loader.getResource(".").getPath() + "/com/example/model";
        File dir = new File(directory);
        //Checking directory already existed or not..
        assertTrue("Directory:"+dir.getPath()+" not exist",dir.exists());
          //Deleting directory 
        deleteDirectoryProgramatically(directory);
        //Checking directory already deleted or not..
        assertFalse("Directory:"+dir.getPath()+" still exist",dir.exists());
        //Now getInstance Method will throw ClassNotFoundException because OkHttpNetworkResponse.Builder.class has been deleted programatically. 
        Factory.getInstance("OkHttpNetworkResponse.Builder.class");
    }

    private void deleteDirectoryProgramatically(String directory) {
        File dir = new File(directory);
        System.out.println(dir.getAbsolutePath());
        String[] files = dir.list();
        for (String f : files) {
            File fl = new File(directory,f);
            System.out.println(f+ " deleted?"+fl.delete());
        }
        System.out.println(dir+ " deleted?"+dir.delete());
    }
}

测试 ClassNotFound 异常

Testing ClassNotFound Exception

java

android

unit-testing

junit4

MyNumber.java

MyNumberTest.java

JUnit - 异常测试