How to test class with @AutoWired using spock

I have a class in src/groovy like this

class MyClass {
@AutoWired
SomeOtherClass someOtherClass

String test() {
    return someOtherClass.testMethod()
}
}

When I write a test for this method I am getting an error: Cannot invoke method testMethod() on null object

This is my test

def "test test" () {
    expect:
        myClass.test() == "somevalue"
}

What am I doing wrong? Is there a way to mock the @AutoWired class?