HttpMock: Accept block arguments

[seanpdoyle]

Extend the ActiveResource::HttpMock declaration DSL to accept a block argument.

When passed a block, the mock will yield an ActiveResource::Request instance to the block it handles a matching request.

def setup
  @matz = { person: { id: 1, name: "Matz" } }

  ActiveResource::HttpMock.respond_to do |mock|
    mock.get "/people.json", omit_query_params: true do |request|
      if request.path.split("?").includes?("name=Matz")
        { people: [ @matz ] }.to_json
      else
        { people: [] }.to_json
      end
    end
  end
end

def test_get_matz
  people = Person.where(name: "Matz")
  assert_equal [ "Matz" ], people.map(&:name)
end

When a block is passed to the mock, it ignores the body, status, and response_headers arguments.