My favorite part of Agile Web Development with Rails is the section on testing. I’ve found the framework around testing included with Rails to be a wonderful blend of simplicity and power and this chapter in the book is the perfect compliment. It’s based largely on the core Ruby Test::Unit module but adds some important features on top.
One of those features is Fixtures. Fixtures provide a simple, YAML-based file format for storing database state that should be loaded before test runs. The database is wiped and the fixtures are loaded before each individual test executes, providing consistent state for tests. See the section on fixtures in A Guide to Testing the Rails for more information. Here’s an example fixture from said section:
# low & behold! I am a YAML comment! david: id: 1 name: David Heinemeier Hansson birthday: 1979-10-15 profession: Systems development steve: id: 2 name: Steve Ross Kellock birthday: 1974-09-27 profession: guy with keyboard
The cool thing is that the top level fixture names (in this case, “david” and “steve”) become instance variables in your test case, allowing you to access fixture data in a very intuitively way from tests. The result of this is test code that reads like a story and is often almost humorous.
Just like the names of variables in general, you want to keep the names of fixtures as self-explanatory as possible. This increases the readability of the tests when you’re asserting that
@valid_order_for_fredis indeed Fred’s valid order. It also makes it a lot easier to remember which fixture you’re supposed to test against without having to look up
order4. The more fixtures you get, the more important it is to pick good fixture names. So, starting early keeps you happy later.
But what to do with fixtures that can’t easily get a self-explanatory name like
@valid_order_for_fred?Pick natural names that you have an easier time associating to a role. For example, instead of using
christmas_order. Instead of
fred. Once you get into the habit of natural names, you’ll soon be weaving a nice little story about how
fredis paying for his
invalid_credit_cardfirst, then paying his
valid_credit_card, and finally choosing to ship it all off to
Association-based stories are key to remembering large worlds of fixtures with ease.
Taking this advice, I started in on testing a part of an application I’m working on now. The result is worth posting in it’s entirety (hint: it gets interesting towards the middle):
require File.dirname(__FILE__) + ‘/../test_helper’ class EnrolleeTest < Test::Unit::TestCase fixtures :coverage_types, :plans, :coverages, :plan_levels, :ppo_options, :elections, :enrollees, :enrollments, :tpas, :tpas_users, :users, :roles def setup @joe = Enrollee.find(@joe_the_policy_holder.id) @rita = Enrollee.find(@rita_the_spouse.id) @billy = Enrollee.find(@billy_the_dependent.id) @alice = Enrollee.find(@alice_the_dependent.id) @the_family = [@joe, @rita, @billy, @alice] @enrollment = Enrollment.find(@test_enrollment.id) end def test_common_attrs @the_family.each do |enrollee| assert_kind_of Enrollee, enrollee assert_equal @enrollment.id, enrollee.enrollment_id assert_equal @enrollment, enrollee.enrollment assert_equal @joe.id, enrollee.policy_holder_id assert_equal @joe, enrollee.policy_holder end end def test_get_gender assert_equal :male, @joe.gender, "Joe is a male" assert @joe.male?, "Joe is a male" assert_equal :female, @rita.gender, "Rita is a female" assert @rita.female?, "Rita is a female" assert !@billy.female?, "Billy is not a female" assert !@alice.male?, "Sally is not a male" end def test_set_gender [:female, ‘F’, 2].each do |tok| @joe.gender = tok assert_equal :female, @joe.gender, "Joe is now a female" assert @joe.save, "Joe could not be saved after sex change" @joe.reload assert_equal :female, @joe.gender, "Joe is now a female" end [:male, ‘M’, 1].each do |tok| @rita.gender = tok assert_equal :male, @rita.gender, "Rita is now a male" assert @rita.save, "Rita could not be saved after sex change" @rita.reload assert_equal :male, @rita.gender, "Rita is now a male" end # make sure that we can set it to nil @joe.gender = nil assert_equal nil, @joe.gender assert @joe.save(false), "Joe couldn’t be saved after neutering…" @joe.reload assert_equal nil, @joe.gender @joe.gender = ‘’ assert_equal nil, @joe.gender assert @joe.save(false), "Joe couldn’t be saved after neutering…" @joe.reload assert_equal nil, @joe.gender end def test_marital_status assert_equal :married, @joe.marital_status assert @joe.married?, "Joe is married" assert !@joe.single?, "Joe is not single" assert @billy.single?, "Billy is single" assert !@billy.married?, "Billy is not married" assert_equal :single, @billy.marital_status end def test_set_marital_status [:married, 2].each do |tok| @billy.marital_status = tok assert_equal :married, @billy.marital_status assert @billy.save, "Billy could not be saved after he got married" @billy.reload assert_equal :married, @billy.marital_status end [:single, 1].each do |tok| @rita.marital_status = tok assert_equal :single, @rita.marital_status assert @rita.save, "Rita could not be saved after her divorce" @rita.reload assert_equal :single, @rita.marital_status end end end