比如我创建一个Kotlin
Object
类:ObjectMethod
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package com.baichuan.example.unit_test
object ObjectMethod {
fun doSomething() {
println( "this is ObjectMethod#doSomething" )
}
@JvmStatic
fun doSomethingWithJvmStatic() {
println( "this is ObjectMethod#doSomethingWithJvmStatic" )
}
}
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如果我直接去mock
该类的doSomething
方法,会报错。
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@Test
@DisplayName ( "mock普通的kotlin静态方法" )
fun testMockKotlinObject() {
Assertions.assertThrows(MissingMethodInvocationException:: class .java) {
Mockito.mockStatic(ObjectMethod:: class .java).`when`<Unit>(
ObjectMethod::doSomething
).thenAnswer { println( "this is mocked Object#doSomething" ) }
}
ObjectMethod.doSomething()
}
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这是因为kotlin
里的object
类里的方法虽然在kotlin
里从形态跟使用上来看与静态方法无二。但是编译成java
代码后,其本质其实是内部初始化了一个当前类的静态常量实例INSTANCE
。这个INSTANCE
在kotlin
语法里被隐藏了,但在java里依然可以显示访问。ObjectMethod
编译成java
后的代码如下:
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public final class ObjectMethod {
@NotNull
public static final ObjectMethod INSTANCE = new ObjectMethod();
private ObjectMethod() {
}
public final void doSomething() {
String var1 = "this is ObjectMethod#doSomething" ;
boolean var2 = false ;
System.out.println(var1);
}
@JvmStatic
public static final void doSomethingWithJvmStatic() {
String var0 = "this is ObjectMethod#doSomethingWithJvmStatic" ;
boolean var1 = false ;
System.out.println(var0);
}
}
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所以,不能mock
ObjectMethod#doSomething
本质上的原因是正常手段无法mock
静态常量。如果想要使kotlin
的object
类中的方法能够被mock
,只需在方法上加上@JvmStatic
注解即可。被其标注的方法会被编译成普通的java
静态方法。
上面说正常手段无法mock静态常量,那么非正常手段呢?其实这个非正常手段就是通过反射将被mock
过的实例注入到ObjectMethod
中即可。
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@Test
@DisplayName ( "通过反射修改静态常量来mock普通的kotlin静态方法" )
fun testMockKotlinObjectMethodByReflection() {
val mock = Mockito.mock(ObjectMethod:: class .java)
Mockito.`when`(mock.doSomething()).then {
print( "this is mocked ObjectMethod by reflection" )
}
val declaredMethod = ObjectMethod:: class .java.getDeclaredField( "INSTANCE" )
ReflectionUtils.setFinalStatic(declaredMethod, mock)
ObjectMethod.doSomething()
}
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ReflectionUtils
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package com.baichuan.example.unit_test
import java.lang.reflect.Field
import java.lang.reflect.Modifier
object ReflectionUtils {
@Throws (Exception:: class )
fun setFinalStatic(field: Field, newValue: Any) {
field.isAccessible = true
val modifiersField: Field = Field:: class .java.getDeclaredField( "modifiers" )
modifiersField.isAccessible = true
modifiersField.setInt(field, field.modifiers and Modifier.FINAL.inv())
field.set( null , newValue)
}
}
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github
https://github.com/scientificCommunity/blog-sample/tree/main/unit-test-sample
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原文链接:https://blog.csdn.net/scientificCommunity/article/details/120258224