RSpec Core provides the structure for writing executable examples of how your code should behave.
gem install rspec # for rspec-core, rspec-expectations, rspec-mocks gem install rspec-core # for rspec-core only
Start with a simple example of behavior you expect from your system. Do this before you write any implementation code:
# in spec/calculator_spec.rb describe Calculator do it "add(x,y) returns the sum of its arguments" do Calculator.new.add(1, 2).should eq(3) end end
Run this with the rspec command, and watch it fail:
$ rspec spec/calculator_spec.rb ./spec/calculator_spec.rb:1: uninitialized constant Calculator
Implement the simplest solution:
# in lib/calculator.rb class Calculator def add(a,b) a + b end end
Be sure to require the implementation file in the spec:
# in spec/calculator_spec.rb # - RSpec adds ./lib to the $LOAD_PATH require "calculator"
Now run the spec again, and watch it pass:
$ rspec spec/calculator_spec.rb . Finished in 0.000315 seconds 1 example, 0 failures
documentation formatter to see the resulting spec:
$ rspec spec/calculator_spec.rb --format doc Calculator add returns the sum of its arguments Finished in 0.000379 seconds 1 example, 0 failures