How do I mock a static method that returns void with PowerMock

Question

I have a few static util methods in my project  some of them just pass or throw an exception  There are a lot of examples out there on how to mock a static method that has a return type other than void  But how can I mock a static method that returns void to just  doNothing      The non-void version uses these lines of codes    PrepareForTest StaticResource class         PowerMockito mockStatic StaticResource class          Mockito when StaticResource getResource  string    thenReturn  string      However if applied to a StaticResources that returns void  the compile will complain that when T  is not applicable for void      Any ideas   A workaround would probably be to just have all static methods return some Boolean for success but I dislike workarounds

User · Answer

To mock a static method that return void for e.g. Fileutils.forceMKdir(File file),

Sample code:

File file =PowerMockito.mock(File.class);
PowerMockito.doNothing().when(FileUtils.class,"forceMkdir",file);

User · Answer

You can stub a static void method like this   PowerMockito doNothing   when StaticResource class   getResource   anyString       Although I m not sure why you would bother  because when you call mockStatic StaticResource class  all static methods in StaticResource are by default stubbed  More useful  you can capture the value passed to StaticResource getResource   like this   ArgumentCaptor lt String gt  captor   ArgumentCaptor forClass String class   PowerMockito doNothing   when                 StaticResource class   getResource   captor capture       Then you can evaluate the String that was passed to StaticResource getResource like this   String resourceName   captor getValue

User · Answer

In simpler terms  Imagine if you want mock below line   StaticClass method      then you write below lines of code to mock   PowerMockito mockStatic StaticClass class   PowerMockito doNothing   when StaticClass class   StaticClass method

User · Answer

You can do it the same way you do it with Mockito on real instances  For example you can chain stubs  the following line will make the first call do nothing  then second and future call to getResources will throw the exception       the stub of the static method doNothing   doThrow Exception class  when StaticResource class   StaticResource getResource  string        the use of the mocked static code StaticResource getResource  string       do nothing StaticResource getResource  string       throw Exception   Thanks to a remark of Matt Lachman  note that if the default answer is not changed at mock creation time  the mock will do nothing by default  Hence writing the following code is equivalent to not writing it   doNothing   doThrow Exception class  when StaticResource class   StaticResource getResource  string      Though that being said  it can be interesting for colleagues that will read the test that you expect nothing for this particular code  Of course this can be adapted depending on how is perceived understandability of the test     By the way  in my humble opinion you should avoid mocking static code if your crafting new code  At Mockito we think it s usually a hint to bad design  it might lead to poorly maintainable code  Though existing legacy code is yet another story   Generally speaking if you need to mock private or static method  then this method does too much and should be externalized in an object that will be injected in the tested object   Hope that helps   Regards

[static] How do I mock a static method that returns void with PowerMock?

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