paulanthonywilson / cat_facts

Example repo illustrating methods of injecting implementations into testing seams. Also fetches cat facts.

CatFacts

Uses the Cat Facts API to illustrate different approaches to creating a Mox style testing seam. See the accompanying blog post here

CatFacts.CatFactsApi is a behaviour and testing seam for extracting Cat Facts from Cat Facts API. It is implemented by CatFacts.RealCatFactsApi and mocked by MockCatFactsApi.

Various versions can be seen with the following tags.

• initial_standard_moxing - the private function CatFacts.CatFactsApi.cat_facts_api/0 reads application config to return the implementation. This is the normal way of doing things.
• accidental_behaviour_tag_deletion - a version in which I "accidentally" forgot to add @behaviour CatFacts.CatFactsApi to CatFacts.RealCatFactsApi. An ommission which will cause problems later.
• rename_but_omit_implementation - CatFacts.CatFactsApi.get_cat_facts/0 has been renamed to CatFacts.fetch_fun_feline_facts/0. Thet tests are passing but I "forgot" to rename the function in CatFacts.RealCatFactsApi.
• alternate_implementation_injection - inject the mock or real implementaton using alias. Still broken but compilation and dialyzer now gives warnings.
• final_working - all working fine again, with the new function name (and the @behaviour restored).