Project: RSpec Mocks 2.0

Publisher: RSpec

Stub a chain of methods

The stub_chain method lets you to stub a chain of methods in one statement.
Method chains are considered a design smell, but it's not really the method
chain that is the problem - it's the dependency chain represented by a chain
of messages to different objects:

foo.get_bar.get_baz

This is a Law of Demeter violation if get_bar() returns an object other than
foo, and get_baz() returns yet another object.

Fluent interfaces look similar from a caller's perspective, but don't
represent a dependency chain (the caller depends only on the object it is
calling). Consider this common example from Ruby on Rails:

Article.recent.by(current_user)

The recent() and by() methods return the same object, so this is not
a Law of Demeter violation.

Scenarios

stub a chain of methods

Given

a file named "stub_chain_spec.rb" with:

describe "stubbing a chain of methods" do
  subject { Object.new }

  context "given symbols representing methods" do
    it "returns the correct value" do
      subject.stub_chain(:one, :two, :three).and_return(:four)
      subject.one.two.three.should eq(:four)
    end
  end

  context "given a string of methods separated by dots" do
    it "returns the correct value" do
      subject.stub_chain("one.two.three").and_return(:four)
      subject.one.two.three.should eq(:four)
    end
  end
end

When

I run "rspec stub_chain_spec.rb"

Then

the output should contain "2 examples, 0 failures"

Last published about 2 years ago by dchelimsky.

Stub a chain of methods

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