Spec::Runner

ExampleGroups and Examples

Rather than expressing examples in classes, RSpec uses a custom DSLL (DSL light) to describe groups of examples.

A ExampleGroup is the equivalent of a fixture in xUnit-speak. It is a metaphor for the context in which you will run your executable example - a set of known objects in a known starting state. We begin be describing

  describe Account do

    before do
      @account = Account.new
    end

    it "should have a balance of $0" do
      @account.balance.should == Money.new(0, :dollars)
    end

  end

We use the before block to set up the Example (given), and then the #it method to hold the example code that expresses the event (when) and the expected outcome (then).

Helper Methods

A primary goal of RSpec is to keep the examples clear. We therefore prefer less indirection than you might see in xUnit examples and in well factored, DRY production code. We feel that duplication is OK if removing it makes it harder to understand an example without having to look elsewhere to understand its context.

That said, RSpec does support some level of encapsulating common code in helper methods that can exist within a context or within an included module.

Setup and Teardown

You can use before and after within a Example. Both methods take an optional scope argument so you can run the block before :each example or before :all examples

  describe "..." do
    before :all do
      ...
    end

    before :each do
      ...
    end

    it "should do something" do
      ...
    end

    it "should do something else" do
      ...
    end

    after :each do
      ...
    end

    after :all do
      ...
    end

  end

The before :each block will run before each of the examples, once for each example. Likewise, the after :each block will run after each of the examples.

It is also possible to specify a before :all and after :all block that will run only once for each behaviour, respectively before the first before :each and after the last after :each. The use of these is generally discouraged, because it introduces dependencies between the examples. Still, it might prove useful for very expensive operations if you know what you are doing.

Local helper methods

You can include local helper methods by simply expressing them within a context:

  describe "..." do

    it "..." do
      helper_method
    end

    def helper_method
      ...
    end

  end

Included helper methods

You can include helper methods in multiple contexts by expressing them within a module, and then including that module in your context:

  module AccountExampleHelperMethods
    def helper_method
      ...
    end
  end

  describe "A new account" do
    include AccountExampleHelperMethods
    before do
      @account = Account.new
    end

    it "should have a balance of $0" do
      helper_method
      @account.balance.should eql(Money.new(0, :dollars))
    end
  end

Shared <a href="/rspec/Spec/Example">Example</a> Groups

You can define a shared <a href="/rspec/Spec/Example">Example</a> Group, that may be used on other groups

 share_examples_for "All Editions" do
   it "all editions behaviour" ...
 end

 describe SmallEdition do
   it_should_behave_like "All Editions"

   it "should do small edition stuff" do
     ...
   end
 end

You can also assign the shared group to a module and include that

 share_as :AllEditions do
   it "should do all editions stuff" ...
 end

 describe SmallEdition do
   it_should_behave_like AllEditions

   it "should do small edition stuff" do
     ...
   end
 end

And, for those of you who prefer to use something more like Ruby, you can just include the module directly

 describe SmallEdition do
   include AllEditions

   it "should do small edition stuff" do
     ...
   end
 end