Why doesn't Module.method_defined?(:method) work correctly?

To know whether the module has a module method, you can use respond_to? on the module:

Something.respond_to?(another)
=> true

method_defined? will tell you whether INSTANCES of the class with the module included responds to the given method.

Modules methods are defined in its metaclass. So you can also check for method inclusion with:

k = class << Something; self; end # Retrieves the metaclass
k.method_defined?(:another)  #=> true

You can read more about it in Understanding Ruby Metaclasses.

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