class_methods.md

Mocking class and module methods

Usually, Mocktail is used to create mock instances of classes and modules, but you may occassionally want or need to mock out the methods defined on a class or module.

To fake out all the methods on a type, you can simply pass it to Mocktail.replace. Here is a little example:

module Substitution
  def self.for(ingredient)
    ingredient.alternatives.first
  end
end

# Somewhere in a test
Mocktail.replace(Substitution)

stubs { Substitution.for(:peychauds_bitters) }.with { :angosutra_bitters }

Substitution.for(:peychauds_bitters)
=> :angosutra_bitters

Heads up!

Mocktail.replace is a spicy operation because it globally mutates that class or module by overwriting its methods. When called, Mocktail does its best to dispatch the real or the fake method based on whether the currently-running thread has faked the type, but this isn't 100% fool-proof, so be wary of potential pollution if you use thread-based test parallelization, and remember to configure an after-each hook to call Mocktail.reset to restore state.

Way to stay classy

Where to go from here?

Head back onto the golden path and use Mocktail to create fake instances of Ruby classes.

Put these overridden classes and modules to good use by stubbing and verifying their methods.