feat([PoC]): Contract for sequence of messages.

[Mifrill]

📓 This PR is just a PoC on how to use Pact for a sequence of messages in a single test iteration. However, this approach is opposite to Consumer-driven Contract Testing (CDC), because is test should be as much simple as possible to test only one iteration (request-response) at a time.

When a Consumer expects a few messages in one test iteration current Pact is keeping only the last message in Contract, this modification makes Pact keeps all messages in Contract.

describe TestMessageConsumer do
  let(:expected_payload_1) {
    {
      "first_name": "John",
      "last_name": "Doe"
    }
  }
  let(:expected_payload_2) {
    {
      "hello": "world"
    }
  }
  let(:consumer) { described_class.new }

  describe "Test Message Consumer", pact: :message do
    it "generates contract" do
      test_message_producer
        .given("Class1")
        .is_expected_to_send("created")
        .with_content(expected_payload_1)
      test_message_producer.send_message_string do |content_string|
        expect(consumer.consume_message(content_string)).to eq(expected_payload_1.to_json)
      end

      test_message_producer
        .given("Class2")
        .is_expected_to_send("updated")
        .with_content(expected_payload_2)
      test_message_producer.send_message_string do |content_string|
        expect(consumer.consume_message(content_string)).to eq(expected_payload_2.to_json)
      end
    end
  end
end

Contract:

{
  "consumer": {
    "name": "Test Message Consumer"
  },
  "provider": {
    "name": "Test Message Producer"
  },
  "messages": [
    {
      "description": "created;updated",
      "providerStates": [
        {
          "name": "Class1",
          "params": {
          }
        },
        {
          "name": "Class2",
          "params": {
          }
        }
      ],
      "contents": [
        {
          "first_name": "John",
          "last_name": "Doe"
        },
        {
          "hello": "world"
        }
      ],
      "matchingRules": {
      }
    }
  ],
  "metadata": {
    "pactSpecification": {
      "version": "2.0.0"
    }
  }
}

See demo: AndrewJanuary/pact-ruby-demo#1

[Mifrill]

📓 It will return an array even for a single record, so when we have only one message content, we show an array [content] in Contract, when we have multiple messages, we show an array of arrays [[Content]]

[Mifrill]

📝 matchingRules is still only for a single message