Question

I’m writing a gem for an API Wrapper that will be used for several applications. I don’t have control over this API but i do have a dev env where i can mess up without affecting production.

How would you write tests for this gem?

Example: consider method add_customer which takes several parameters ( name, email etc. ) with email being unique.

If i write a test that inserts a customer with email [e-mail]. At the second time, this test will fail although my gem is properly working.

Answer 1

Normally you would like to clean up your db for each test you are running. We are using the DatabaseCleaner gem to do this in ruby. Basically before we run the whole suite we completely clean the database with

DatabaseCleaner.clean_with :truncation

This takes some time depending on your db. After that we use the transaction strategy to keep it faster

DatabaseCleaner.strategy = :transaction

This means that before every spec a transaction is started in the db(a save point is created) and the test runs in this transaction. After the test has finished, a rollback is issued and the next spec has a clean db again. Check out https://github.com/bmabey/database_cleaner

If you do need to create two such records in the same spec though then you will need to create some kind of counter. Something like:

class Counter
  def initialize
    @count = 0
  end

  def email
    @count += 1
    "something_cool#{@count}@whatever.com"
  end
end

And then use this counter to give you a unique e-mail every time. It might be worth the while to check out the FactoryGirl gem https://github.com/thoughtbot/factory_girl/wiki/Usage and look for sequence. If you are building a small gem though then you’d probably not want to add a lot of dependencies. Good Luck. TDD all the way!

Not having control over all parts of the system makes for a bigger problem. In unit tests you can happily stub away all external APIs and just return the expected results. But of course this will still be passing if the API changes. Integration tests of distributed systems is kind of a complex issue and basically you would need something like system-wide transactions that will put all the parts of the system into the original state. Since you do not have that control I would just stub away.