[英]Java Mockit : How to Mock a generic class method in JMockit
Hi I have the following classes 嗨,我有以下课程
public class DataAccessLayer<T> {
public T getData(Class<?> dataInfoType ,Integer id){
//Some logic here
}
}
public class ServiceLayer{
//this method has to be tested
public Integer testingMethode{
//The following line should be mocked
UtilClass info = new DataAccessLayer<UtilClass>().getData(UtilClass.class, 1);
retutn info.getSomeFieldWithIntegerValue();
}
}
I want to write test cases for testingMethode for that I need to mock the getData()
method in DataAccessLayer<T>
我想为testingMethode编写测试用例,因为我需要在
DataAccessLayer<T>
模拟getData()
方法
Is it possible with jmockit
to mock a Template(Generic ) class? jmockit
是否可以模拟Template(Generic)类?
In JMockit there's actually no need to create a holding variable in the ServiceLayer
class, nor is there a need to make a parameterized subclass of your DataLayer
. 在JMockit中,实际上不需要在
ServiceLayer
类中创建一个保持变量,也不需要为DataLayer
创建参数化的子类。 The following test works just fine: 以下测试可以正常工作:
package com.example.dsohl;
import static org.hamcrest.Matchers.equalTo;
import static org.junit.Assert.assertThat;
import org.junit.Test;
import org.junit.runner.RunWith;
import mockit.Deencapsulation;
import mockit.Expectations;
import mockit.Mocked;
import mockit.Tested;
import mockit.integration.junit4.JMockit;
@RunWith(JMockit.class)
public class TestTest {
public static class UtilClass {
public Integer foo() {
return 5;
}
}
public static class DataLayer<T> {
public T getItem(Class<T> clazz, int itemId) {
return null;
}
}
public static class ServiceLayer {
public Integer testMethod() {
UtilClass util = new DataLayer<UtilClass>().getItem(UtilClass.class, 1);
return util.foo();
}
}
// Test really begins here
@Tested ServiceLayer svc;
@Mocked DataLayer<UtilClass> data;
@Mocked UtilClass util;
@Test
public void testDateSubtraction() throws Exception {
new Expectations() {
{
new DataLayer<UtilClass>(); result = data;
onInstance(data).getItem(UtilClass.class, 1); result = util;
util.foo(); result = 37;
}
};
Integer i = svc.testMethod();
assertThat(i, equalTo(37));
}
}
A few notes: First, my DataLayer.getItem()
returns null so if the injection fails, we get a NullPointerException
, nice and obvious. 一些注意事项:首先,我的
DataLayer.getItem()
返回null,因此,如果注入失败,我们将得到NullPointerException
,很明显。 Obviously your code won't work like this; 显然,您的代码无法像这样工作; this is only to convince you.
这只是说服您。
Second, I use onInstance()
so that we can be 100% certain that the result of the DataLayer
constructor is what we are using in the next steps of the test. 其次,我使用
onInstance()
以便可以100%确定DataLayer
构造函数的结果是我们在测试的下一步中使用的结果。 The default behaviour of Expectations
on a @Mocked
object is to record the expectation against any object of that class; @Mocked
对象上的Expectations
的默认行为是针对该类的任何对象记录期望; this is how we are certain that it's our object that's being used. 这就是我们确定正在使用的是我们的对象的方式。 (Ordinarily I don't worry myself about this, but when using
new
I like to be certain.) (通常我不必为此担心,但是在使用
new
我想确定一下。)
Finally, I'm omitting some other stuff I might do in cases like this, like use a Verifications
block, etc. Just trying to be as straightforward as possible. 最后,我省略了在这种情况下可能要做的其他事情,例如使用
Verifications
块等。只是尝试尽可能简单明了。
Enjoy! 请享用!
A generic class can be mocked the same way a non-generic one: 通用类可以像非通用类一样进行模拟:
@Test
public void example(@Mocked final DataAccessLayer<UtilClass> mock)
{
final UtilClass data = new UtilClass(123);
new Expectations() {{ mock.getData(UtilClass.class, 1); result = data; }};
int result = new ServiceLayer().testingMethode();
assertEquals(123, result);
}
(I can only really answer for Mockito, as that is what I am most familiar with; but the same principle should be applicable in other mocking frameworks). (我只能真正回答Mockito,因为这是我最熟悉的;但是相同的原理应该适用于其他模拟框架)。
Firstly, you need to be able to inject a DataAccessLayer<UtilClass>
into ServiceLayer
, eg 首先,您需要能够将
DataAccessLayer<UtilClass>
注入ServiceLayer
,例如
class ServiceLayer {
private final DataAccessLayer<UtilClass> dal;
ServiceLayer(DataAccessLayer<UtilClass> dal) {
this.dal = dal;
}
public Integer testingMethode() {
UtilClass info = dal.getData(UtilClass.class, 1);
return info.getSomeFieldWithIntegerValue();
}
}
This breaks the static coupling to the DataAccessLayer<UtilClass>
created by the use of the new
. 这打破了与使用
new
创建的DataAccessLayer<UtilClass>
的静态耦合。
Now, you can create a mocked instance of DataAccessLayer<UtilClass>
by creating a non-generic subclass: 现在,您可以通过创建一个非通用子类来创建
DataAccessLayer<UtilClass>
的DataAccessLayer<UtilClass>
实例:
class UtilClassDataAccessLayer extends DataAccessLayer<UtilClass> {}
and then create a mock instance: 然后创建一个模拟实例:
DataAccessLayer<UtilClass> mocked = mock(UtilClassDataAccessLayer.class);
Now, you can configure this mock as you need, and pass it into the ServiceLayer
: 现在,您可以根据需要配置此模拟,并将其传递给
ServiceLayer
:
ServiceLayer serviceLayer = new ServiceLayer(mocked);
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