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
Use the 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