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RSpec Core

Behaviour Driven Development for Ruby

Upgrading from rspec-1.x

See Upgrade.markdown


gem install rspec --prerelease

This will install the rspec, rspec-core, rspec-expectations and rspec-mocks gems.

Get Started

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, "add" do
  it "returns the sum of its arguments" do, 2).should eq(3)

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

Be sure to require the implementation file in the spec:

# in spec/calculator_spec.rb
# - RSpec adds ./lib to the $LOAD_PATH, so you can
#   just require "calculator" directly
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

Known issues


Learn more

While not comprehensive yet, you can learn quite a lot from the Cucumber features in the features directory. If there is a feature that is not documented there, or you find them insufficient to understand how to use a feature, please submit issues to



Also see

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