单元测试，使用 Context 作为变量在 Kotlin 中使用 PowerMock 模拟静态方法

Question

这是一场噩梦。

在单元测试中，我有一个具有一个功能的助手：

open class SharedPreferencesHelper {

    companion object {
        open fun loadString(context: Context, fileName: String, key: String, defaultValue: String?): String? {
            val sharedPreferences = getWithFileName(context, fileName)
            return if (!sharedPreferences.contains(key)) {
                defaultValue
            } else {
                sharedPreferences.getString(key, defaultValue)
            }
        }

        open fun getWithFileName(context: Context, fileName: String): SharedPreferences {
            return context.getSharedPreferences(fileName, MODE_PRIVATE)
        }
    }
}

我想将该函数模拟为 return "foo"

第一次尝试

@RunWith(PowerMockRunner::class)
@PrepareForTest(ConfigUseCase::class, SharedPreferencesHelper::class)
class ConfigUseCaseTests : UnitTestsResource() {

    private lateinit var configUseCase: ConfigUseCase

    @JvmField
    @ClassRule
    var rule = PowerMockRule()

    @Before
    override fun setUp() {
        super.setUp()
        configUseCase = ConfigUseCase()
    }

    @Test
    fun getConfigs_fromJson() {
        mockStatic(SharedPreferencesHelper::class.java)
        whenever(SharedPreferencesHelper.loadString(isA(), anyString(), anyString(), anyString())).thenReturn("foo")
    }
}

结果：

java.lang.IllegalArgumentException: Parameter specified as non-null is null: method my.package.helpers.sharedPreferences.SharedPreferencesHelper$Companion.loadString, parameter context

    at my.package.helpers.sharedPreferences.SharedPreferencesHelper$Companion.loadString(SharedPreferencesHelper.kt)
    at my.package.ConfigUseCaseTests.getConfigs_fromJson(ConfigUseCaseTests.kt:39)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:68)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:310)
    at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:89)
    at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:97)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.executeTest(PowerMockJUnit44RunnerDelegateImpl.java:294)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTestInSuper(PowerMockJUnit47RunnerDelegateImpl.java:127)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTest(PowerMockJUnit47RunnerDelegateImpl.java:82)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:282)
    at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:87)
    at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:50)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.invokeTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:207)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:146)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:120)
    at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:34)
    at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:44)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:122)
    at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:106)
    at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:53)
    at org.powermock.modules.junit4.PowerMockRunner.run(PowerMockRunner.java:59)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMainV2.main(AppMainV2.java:131)

使用 context 作为模拟

@Test
fun getConfigs_fromJson() {
    val context = mock<Context>()
    mockStatic(SharedPreferencesHelper::class.java)
    whenever(SharedPreferencesHelper.loadString(context, anyString(), anyString(), anyString())).thenReturn("foo")
}

结果：

org.mockito.exceptions.misusing.InvalidUseOfMatchersException: 
Invalid use of argument matchers!
2 matchers expected, 3 recorded:
-> at my.package.ConfigUseCaseTests.getConfigs_fromJson(ConfigUseCaseTests.kt:41)
-> at my.package.ConfigUseCaseTests.getConfigs_fromJson(ConfigUseCaseTests.kt:41)
-> at my.package.ConfigUseCaseTests.getConfigs_fromJson(ConfigUseCaseTests.kt:41)

This exception may occur if matchers are combined with raw values:
    //incorrect:
    someMethod(anyObject(), "raw String");
When using matchers, all arguments have to be provided by matchers.
For example:
    //correct:
    someMethod(anyObject(), eq("String by matcher"));

For more info see javadoc for Matchers class.


    at my.package.helpers.sharedPreferences.SharedPreferencesHelper$Companion.getWithFileName(SharedPreferencesHelper.kt:22)
    at my.package.helpers.sharedPreferences.SharedPreferencesHelper$Companion.loadString(SharedPreferencesHelper.kt:38)
    at my.package.ConfigUseCaseTests.getConfigs_fromJson(ConfigUseCaseTests.kt:41)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:68)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:310)
    at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:89)
    at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:97)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.executeTest(PowerMockJUnit44RunnerDelegateImpl.java:294)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTestInSuper(PowerMockJUnit47RunnerDelegateImpl.java:127)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTest(PowerMockJUnit47RunnerDelegateImpl.java:82)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:282)
    at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:87)
    at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:50)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.invokeTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:207)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:146)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:120)
    at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:34)
    at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:44)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:122)
    at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:106)
    at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:53)
    at org.powermock.modules.junit4.PowerMockRunner.run(PowerMockRunner.java:59)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMainV2.main(AppMainV2.java:131)

这是调用方法 loadString 而不是忽略它并 returning "foo"

我还应该做什么？

Answer 1

它创建了一个 Companion 的实例，例如：

@Test
fun getConfigs_fromJson() {
    val instance = mock<SharedPreferencesHelper.Companion>()
    whenever(instance.loadString(isA(), anyString(), anyString(), anyString())).thenReturn("foo")
    PowerMockito.whenNew(SharedPreferencesHelper.Companion::class.java)
            .withAnyArguments()
            .thenReturn(instance)

    System.out.println("HEY: ${SharedPreferencesHelper.loadString(context, "", "", null)}")
}

Answer 2

查看您上次使用 context 作为模拟的尝试，我可以看出一个非常常见的错误。请注意错误的堆栈跟踪如何指出 Matchers -> org.mockito.exceptions.misusing.InvalidUseOfMatchersException:

的不正确使用

这是因为在模拟时，您在以下行中使用了 context、anyString()、anyString() 和 anyString()：

whenever(SharedPreferencesHelper.loadString(context, anyString(), anyString(), anyString())).thenReturn("foo")

解法：

因为 anyString() returns 一个 Matcher，您也可以通过对 context 使用 Matcher 来解决该错误。例如，使用：eq(context):

whenever(SharedPreferencesHelper.loadString(eq(context), anyString(), anyString(), anyString())).thenReturn("foo")

单元测试，使用 Context 作为变量在 Kotlin 中使用 PowerMock 模拟静态方法

Unit Tests, mocking static method using Context as variable in Kotlin with PowerMock

android

unit-testing

mockito

powermockito