spock - mock static method is not working

Question

I am trying to mock the one of static method readAttributes using groovy's metaClass convention, but the real method get invoked.

This is how I mocked the static function:

def "test"() {
    File file = fold.newFile('file.txt')
    Files.metaClass.static.readAttributes = { path, cls ->
        null
    }

    when:
        fileUtil.fileCreationTime(file)
    then:
        1 * fileUtil.LOG.debug('null attribute')
}

Am I doing something wrong here?

My java method

public Object fileCreationTime(File file) {
    try {
        BasicFileAttributes attributes = Files.readAttributes(file.toPath(), BasicFileAttributes.class);
        if(attributes == null) {
            LOG.debug("null attribute");
        }  
        //doSomething
    } catch (IOException exception) {
        //doSomething
    }
    return new Object();
}

Solution 1

I resolved the issue using one level of indirection. I created an instance method of the test class which acts like a wrapper for this static call.

public BasicFileAttributes readAttrs(File file) throws IOException {
    return Files.readAttributes(file.toPath(), BasicFileAttributes.class);
}

and from the test I mocked the instance method.

FileUtil util = Spy(FileUtil);
util.readAttrs(file) >> { null }

which resolved my issue.

Solution 2

The short answer is that it's not possible, please have a look at this question.

It would be possible if either:

• code under test was written in groovy
• mocked (altered) class must be instantiated in groovy code.

The workaround is to extract the logic returning the attributes to another class which will be mocked instead of use Files directly.

Solution 3

you can use GroovySpy for this, as stated in spock documentation

In your case, it would be:

def filesClass = GroovySpy(Files, global: true)
filesClass.readAttributes(*_) >> null

Comments

[Opal]

@Suganthan have you copied the example I provided as is? Cloaure's args are also very important.

[Suganthan Madhavan Pillai]

Yes, I did the same, the intermediate assertion workd with no issue, but still the method get invoked

[Opal]

@Suganthan could you please then provide na runnable example? Without it, it might difficult to help.

[Opal]

@Suganthan, if you found my answer useful please accept and upvote it.

[Suganthan Madhavan Pillai]

I thought it is due to final class(Files) and it is private method is a root cause

[Opal]

@Suganthan, final classes can be mocked as well, see here

[Suganthan Madhavan Pillai]

Sorry it is not private method private constructor. Private Constructor might be a cause. Files having private constructor, but not the String class

[Opal]

@Suganthan, may be. However in groovy private is not private at all ;)

[Suganthan Madhavan Pillai]

Yes, that make sense, sure I ll to find out the root cause and update my answer :)

[imy]

This does not work when mocking static (Java) class within the object of test. In other words, the one instantiated not from Groovy. See stackoverflow.com/questions/15824315/…