rspec_kwargs_spec.rb

require "rspec"
RSpec.configure do |config|
  config.expect_with :rspec do |expectations|
    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
  end

  config.mock_with :rspec do |mocks|
    mocks.verify_partial_doubles = true
  end
end

class ClassWeMock
	def mocked_method(a: , b: )
		a + b
	end
end

class UsesKwargs
	def doit(foo)
		bar = ClassWeMock.new.mocked_method(a: foo, b: 10)
		bar + 1
	end
end

class UsesHash
	def doit(foo)
		hash = { a: foo, b: 10 }
		bar = ClassWeMock.new.mocked_method(hash)
		bar + 1
	end
end

RSpec.describe UsesKwargs do
	subject(:uses_kwargs) { described_class.new }
	describe "#doit" do
		it "calls into ClassWeMock" do
			class_we_mock = instance_double(ClassWeMock)
			allow(ClassWeMock).to receive(:new).and_return(class_we_mock)
			allow(class_we_mock).to receive(:mocked_method).and_return(99)

			result = uses_kwargs.doit(20)

			expect(result).to eq(100)
			expect(class_we_mock).to have_received(:mocked_method).with(a: 20, b: 10)
		end
	end
end

RSpec.describe UsesHash do
	subject(:uses_kwargs) { described_class.new }
	describe "#doit" do
		it "calls into ClassWeMock" do
			class_we_mock = instance_double(ClassWeMock)
			allow(ClassWeMock).to receive(:new).and_return(class_we_mock)
			allow(class_we_mock).to receive(:mocked_method).and_return(99)

			result = uses_kwargs.doit(20)

			expect(result).to eq(100)
			expect(class_we_mock).to have_received(:mocked_method).with(a: 20, b: 10)
		end
	end
end

if ARGV[0] == "run"
	puts "UsesKwargs"
	puts UsesKwargs.new.doit(20)

	puts "UsesHash"
	begin
		puts UsesHash.new.doit(20)
	rescue ArgumentError => ex
		puts ex.message
	end
end