比如我創建一個Kotlin Object類：ObjectMethod
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package com.baichuan.example.unit_testobject ObjectMethod { fun doSomething() { println("this is ObjectMethod#doSomething") } @JvmStatic fun doSomethingWithJvmStatic() { println("this is ObjectMethod#doSomethingWithJvmStatic") }} |
如果我直接去mock該類的doSomething方法，會報錯。
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@Test@DisplayName("mock普通的kotlin靜態方法")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()} |
這是因為kotlin里的object類里的方法雖然在kotlin里從形態跟使用上來看與靜態方法無二。但是編譯成java代碼后，其本質其實是內部初始化了一個當前類的靜態常量實例INSTANCE。這個INSTANCE在kotlin語法里被隱藏了，但在java里依然可以顯示訪問。ObjectMethod編譯成java后的代碼如下：
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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); }} |
所以，不能mock ObjectMethod#doSomething本質上的原因是正常手段無法mock靜態常量。如果想要使kotlin的object類中的方法能夠被mock，只需在方法上加上@JvmStatic注解即可。被其標注的方法會被編譯成普通的java靜態方法。
上面說正常手段無法mock靜態常量，那么非正常手段呢？其實這個非正常手段就是通過反射將被mock過的實例注入到ObjectMethod中即可。
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@Test@DisplayName("通過反射修改靜態常量來mock普通的kotlin靜態方法")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()} |
ReflectionUtils
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package com.baichuan.example.unit_testimport java.lang.reflect.Fieldimport java.lang.reflect.Modifierobject 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) }} |
github
https://github.com/scientificCommunity/blog-sample/tree/main/unit-test-sample
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原文鏈接：https://blog.csdn.net/scientificCommunity/article/details/120258224
