Short note on a repeatable starting point for TDD
For testing to be useful, it needs to be repeatable. Curious, here’s some notes I took when investigating what happens when you run ‘rake spec’. This also would apply similarly for cucumber.
Rspec:
rspec specs can be run in various ways:
$ rake spec $ spec spec $ spec spec/controller/somefile_spec.rb $ spec spec/controller/somefile_spec.rb:31 # specify a line number $ autospec # ( see http://zentest.rubyforge.org/ZenTest/ for docs or even better, check the source. )
Only the first command sets up the environment from scratch. The other methods assume a working environment and if your tests assume a working environment and that assumption is invalid, then boom!
What happens in a rake spec? Here’s what I see when I run it (edited for brevity and comments added)
$ rake --trace spec | grep Execute # ignore the Invoke lines. we're only interested in what actually gets run (in /Users/eddykim/work/coupa_gitrepo) ** Execute environment ** Execute db:abort_if_pending_migrations ** Execute db:test:prepare ** Execute db:test:purge #-- drops all the tables in the db ** Execute db:test:load #-- creates the tables, using schema.rb (does not populate the tables with any data) ** Execute db:schema:load #-- is this really necessary for the test db? ** Execute spec
The following is the bare minimum of things that need to be setup a clean and working database before you start your TDD mojo.
$ rake db:test:purge $ rake db:test:load $ RAILS_ENV=test rake db:seed:load SEEDS='all' # (This is a custom task in our project)
Notice that I skip running the db:schema:load which seems to be an unnecessary, time sucking task. At which point you can run spec manually, or autospec if you so desire.
Additionally, the db:seeds:load task has a similar function as running rake db:fixtures:load.
Moral of the story: Make sure your test database is in a known good starting state before running your tests. But to keep your testing speed up, you don’t need to re-setup the db on every test run if you are using transactions to keep your test db clean.
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