How to run your specific espresso test class/test cases using spoon?

Question

I tried adding :

spoon {
     if (project.hasProperty('spoonClassName')) {
         className = project.spoonClassName  
        }
    }

But i am getting below mentioned error : A problem occurred evaluating root project 'AndroidTestApp'.

Could not find method spoon() for arguments [build_efbwwyd8gychv00diqry4hwki$_run_closure1$_closure3$_closure7@1c104303] on repository container of type org.gradle.api.internal.artifacts.dsl.DefaultRepositoryHandler.

Can anybody tell me how to exactly add above snippet and in which gradle file ?