java - 尝试模拟 java.lang.System 时出现 MockitoException

Question

我有一个模拟 java.lang.System 的静态方法的测试用例类(class):

@Test
fun `getLocalTime()`() {
    // Arrange
    val staticMock = Mockito.mockStatic(System::class.java)
    Mockito.`when`(System.currentTimeMillis()).thenReturn(1000L)

    // Action
    val res = deviceTimeProvider.getLocalTime()

    // Assert
    Truth.assertThat(res).isEqualTo(1000L)

    staticMock.close()
}

但是当我运行测试时，我得到了这个错误:

org.mockito.exceptions.base.MockitoException: It is not possible tomock static methods of java.lang.System to avoid interfering withclass loading what leads to infinite loops

为什么会这样？如何模拟 java.lang.System 的方法类(class)？

Answer 1

而 Mockito 自 3.4.0版本允许模拟静态方法它不允许模拟 Thread和 System静态方法，见 this comment on github

Finally note that Mockito forbids mocking the static methods of System (and Thread). Those methods are to much cemented into class loading which happens in the same thread. At some point, we might add instrumentation to class loading to temporarily disable the static mocks within it to make mocking these classes, too, where we also would need to disable their intensification properties. You can however easily mock Instant.now().