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Project: RSpec Rails 2.2

Publisher: RSpec

mock_model

The mock_model method generates a test double object that acts like an
Active Model model. This is different from the stub_model method which
generates an instance of a real ActiveModel class.

The benefit of mock_model over stub_model is that its a true double, so the
examples are not dependent on the behaviour (or mis-behaviour), or even the
existence of any other code. If you're working on a controller spec and you
need a model that doesn't exist, you can pass mock_model a string and the
generated object will act as though its an instance of the class named by
that string.

Scenarios
  1. passing a string that represents a non-existent constant
  2. passing a string that represents an existing constant
  3. passing a class that does not extend ActiveModel::Naming
  4. passing an Active Record constant
  5. passing an Active Record constant with method stubs
passing a string that represents a non-existent constant
Given
a file named "spec/models/car_spec.rb" with: 
require "spec_helper"

describe "mock_model('Car') with no Car constant in existence" do
  it "generates a constant" do
    Object.const_defined?(:Car).should be_false
    mock_model("Car")
    Object.const_defined?(:Car).should be_true
  end

  describe "generates an object that ..." do
    it "returns the correct name" do
      car = mock_model("Car")
      car.class.name.should eq("Car")
    end

    it "says it is a Car" do
      car = mock_model("Car")
      car.should be_a(Car)
    end
  end
end
When
I run "rspec spec/models/car_spec.rb"
Then
the output should contain "3 examples, 0 failures"
passing a string that represents an existing constant
Given
a file named "spec/models/widget_spec.rb" with: 
require "spec_helper"

describe Widget do
  it "uses the existing constant" do
    widget = mock_model("Widget")
    widget.should be_a(Widget)
  end
end
When
I run "rspec spec/models/widget_spec.rb"
Then
the output should contain "1 example, 0 failures"
passing a class that does not extend ActiveModel::Naming
Given
a file named "spec/models/string_spec.rb" with: 
require "spec_helper"

describe String do
  it "raises" do
    expect { mock_model(String) }.to raise_exception
  end
end
When
I run "rspec spec/models/string_spec.rb"
Then
the output should contain "1 example, 0 failures"
passing an Active Record constant
Given
a file named "spec/models/widget_spec.rb" with: 
require "spec_helper"

describe Widget do
  let(:widget) { mock_model(Widget) }

  it "is valid by default" do
    widget.should be_valid
  end

  it "is not a new record by default" do
    widget.should_not be_new_record
  end

  it "can be converted to a new record" do
    widget.as_new_record.should be_new_record
  end

  it "sets :id to nil upon destroy" do
    widget.destroy
    widget.id.should be_nil
  end
end
When
I run "rspec spec/models/widget_spec.rb"
Then
the output should contain "4 examples, 0 failures"
passing an Active Record constant with method stubs
Given
a file named "spec/models/widget_spec.rb" with: 
require "spec_helper"

describe "mock_model(Widget) with stubs" do
  let(:widget) do
    mock_model Widget, :foo => "bar",
                       :save => true,
                       :update_attributes => false
  end

  it "supports stubs for methods that don't exist in ActiveModel or ActiveRecord" do
    widget.foo.should eq("bar")
  end

  it "supports stubs for methods that do exist" do
    widget.save.should eq(true)
    widget.update_attributes.should be_false
  end

  describe "#errors" do
    context "with update_attributes => false" do
      it "is not empty" do
        widget.errors.should_not be_empty
      end
    end
  end
end
When
I run "rspec spec/models/widget_spec.rb"
Then
the output should contain "3 examples, 0 failures"

Last published almost 7 years ago by dchelimsky.