java - stub 时 PowerMockito NullPointerException

Question

我想使用以下测试代码对 java.nio.file.Files 中的公共(public)静态函数 readAllBytes 进行 stub 。

@PrepareForTest(Files.class)
public void testGetNotExistingRestFile() throws Exception {
    PowerMockito.mockStatic(Files.class);
    PowerMockito.doThrow(mock(IOException.class)).when(Files.readAllBytes(any(Path.class)));
}

每次抛出 NullPointerException 时，我都能弄清楚我做错了什么。

java.lang.NullPointerException
at java.nio.file.Files.provider(Files.java:67)
at java.nio.file.Files.newByteChannel(Files.java:317)
at java.nio.file.Files.newByteChannel(Files.java:363)
at java.nio.file.Files.readAllBytes(Files.java:2981)
at nl.mooij.bob.RestFileProviderTest.testGetNotExistingRestFile(RestFileProviderTest.java:53)

如何使用 PowerMockito stub java.nio.file.Files 中的 readAllBytes 函数？

Answer 1

调用 Mockito，而不是 PowerMockito 并反转 stub 顺序:

@Test(expected=IOException.class)
@PrepareForTest(Files.class)
public void testGetNotExistingRestFile() throws Exception {
    // arrange
     PowerMockito.mockStatic(Files.class);
     Mockito.when(Files.readAllBytes(Matchers.any(Path.class))).thenThrow(Mockito.mock(IOException.class));
    // act
     Files.readAllBytes(Mockito.mock(Path.class));
}

另一种可能是:

   @Test(expected=IOException.class)
   @PrepareForTest(Files.class)
   public void testGetNotExistingRestFile() throws Exception {
     // arrange
       PowerMockito.mockStatic(Files.class);
       Files filesMock = PowerMockito.mock(Files.class);
       Mockito.when(filesMock.readAllBytes(Matchers.any(Path.class))).thenThrow(Mockito.mock(IOException.class));
     // act   
       filesMock.readAllBytes(Mockito.mock(Path.class));
   }

引用:Using PowerMockito to Mock Final and Static Methods