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Project: RSpec Mocks 3.7

Publisher: RSpec

Wrapping the original implementation

Use and_wrap_original to modify a partial double's original response. This can be useful
when you want to utilise an external object but mutate its response. For example if an
API returns a large amount of data and for test purposes you'd like to trim it down. You can
also use it to configure the default response for most arguments, and then override that for
specific arguments using with.

Note: and_wrap_original is only supported on partial doubles, as normal test doubles do
not have an original implementation.

Background
Given
a file named "lib/api.rb" with: 
class API
  def self.solve_for(x)
    (1..x).to_a
  end
end
Scenarios
`and_wrap_original` wraps the original partial double response
Given
a file named "spec/and_wrap_original_spec.rb" with: 
require 'api'

RSpec.describe "and_wrap_original" do
  it "responds as it normally would, modified by the block" do
    expect(API).to receive(:solve_for).and_wrap_original { |m, *args| m.call(*args).first(5) }
    expect(API.solve_for(100)).to eq [1,2,3,4,5]
  end
end
When
I run rspec spec/and_wrap_original_spec.rb
Then
the examples should all pass
`and_wrap_original` can configure a default response that can be overriden for specific args
Given
a file named "spec/and_wrap_original_spec.rb" with: 
require 'api'

RSpec.describe "and_wrap_original" do
  it "can be overriden for specific arguments using #with" do
    allow(API).to receive(:solve_for).and_wrap_original { |m, *args| m.call(*args).first(5) }
    allow(API).to receive(:solve_for).with(2).and_return([3])

    expect(API.solve_for(20)).to eq [1,2,3,4,5]
    expect(API.solve_for(2)).to eq [3]
  end
end
When
I run rspec spec/and_wrap_original_spec.rb
Then
the examples should all pass

Last published 10 months ago by myronmarston.