This document provides an overview of consumer-driven contracts (CDC) and the Pact framework for implementing CDC. It defines CDC as a pattern where consumers capture expectations of providers in separate contract files (called pacts) that are shared with providers. This allows providers to validate that their implementations meet the consumers' expectations. The document then describes how Pact works, including capturing interactions on the consumer side, generating a pact file, and validating interactions on the provider side. It highlights advantages of CDC like reducing assumptions, enabling communication, and failing fast. The second half demonstrates setting up a mock provider and expectations on the consumer side, making a request and assertion, and validating the pact on the provider side.

1. Consumer Driven Contracts
A Deep Dive
Ramya Authappan
Lead SDET, Freshworks

2. Few Things About Myself
www.facebook.com/at.ramya
@atramya
https://www.linkedin.com/in/ramy
aat/
ramya.authappan@freshworks.c
om
http://tiny.cc/ramya_talks
Lead SDET @ Freshworks
Passionate about
building/designing Test
Frameworks/Tools
Believes in building “Simple, yet
Powerful” tools
Loves to play with Sharon

3. About Freshworks
• SAAS Startup
• Believes in building software that’s ready to go, easy to setup and use, and
requires minimal customization.
• Global Presence:
• Investors:
• Products:

4. CDC - Consumer Driven Contract!
• Microservices @ Amazon
• Talks to each other via HTTP Requests
• How do I make sure that a simple change does not break
anything in the application? An integration nightmare!
• In such a system, how do I independently AND
confidently make changes?
• CDC to the RESCUE!

5. CDC - Consumer Driven Contract!
• Consumer-Driven Contracts is a pattern defined by Martin Fowler.
• In Consumer-Driven Contracts, each consumer captures their expectations of the provider in a separate contract
(pact).
• All of these contracts are shared with the provider so they gain insight into the obligations they must fulfil for each
individual client.
• Implementations:
• Pact - https://docs.pact.io/ - This is what we will use in this session.
• Pacto - https://github.com/thoughtworks/pacto
• Janus - https://github.com/gga/janus
• Spring Cloud Contract - https://cloud.spring.io/spring-cloud-contract/ - Found this implementation few days
back. - Java Implementation

6. CDC - Consumer Driven Contract!
• What is Pact? - An opensource library implementing CDC
• Available as ruby gems (gem: ‘pact’) and as npm packages
(‘pact’)
• Supports: Ruby, Java, .NET
• Beta: JS,Python, Swift, Go
• Its called “Asynchronous” Integration Tests - No extra setup
needed.
• As simple as unit tests but as powerful as E2E tests.
• Pact is run on both sides - On “Consumer” side and on
“Provider” side.

7. CDC - Consumer Side
Sends
response
for
assertions
Tests
Set
Expectations
Pact Mock Provider
Tests
invoke
code
Source Code
Sends
HTTP
Requests
Sends
expected
response

8. CDC - Pact File
DevPortal Activities
Request
Response
Consumer Provider

9. CDC - Pact File!
• Every HTTP Request and Response is
captured
• Standard way of representing interactions -
JSON file
• This is shared with the Provider.
• Explains everything that a consumer expects
from the Provider - the endpoints, query
params, header and the response objects.

10. CDC - Provider Side
Activities
Replay each HTTP Request
Get real HTTP Response
Provider
Pact File Compares real and
mock responses

11. CDC - Provider States
• Get activities of user with id=777
DevPortal Activities
Request
Response
Consumer Provider
Request
Response
?

12. CDC - Provider Side
state: cust_id=777 @ DB
• Get activities of user with id=777
DevPortal Activities
Request
Response
Consumer
Provider
Request
Response
state: cust_id=777 @ DB
state: cust_id=777 @ DB

13. CDC - Sharing Pact Files
Filesystem Cloud Pact BrokerCI Build
Artefact

14. CDC - Advantages!
• Eliminates Wrong Assumptions
• Enables communication
• Very less setup time!
• No extra infrastructure
• Need not start the dependent services to test!
• Fast in Execution
• Fails Fast - Identifies integration issues even before you actually
integrate!
• No flakiness!
• Easy to debug

15. Demo

16. Consumer Side : Setup Mock Server
Pact.service_consumer 'DevPortal' do
end

17. Consumer Side : Setup Mock Server
Pact.service_consumer 'DevPortal' do
has_pact_with "Freshapps Activities" do
end
end

18. Consumer Side : Setup Mock Server
Pact.service_consumer 'DevPortal' do
has_pact_with "Freshapps Activities" do
mock_service :freshapps_activities do
port 3005
end
end
end

19. Consumer Side : Setup Expectations
freshapps_activities.given(“all activities without role param")

20. Consumer Side : Setup Expectations
freshapps_activities.given(“all activities without role param")
.upon_receiving("a request for all activities")
.with(
method: :get,
path: '/all/activities.json',
query: {
page: '1',
account_id: '1' },
headers: {'Content-Type' => 'application/json', 'Accept' => 'application/json'} )

21. Consumer Side : Setup Expectations
freshapps_activities.given(“all activities without role param")
.upon_receiving("a request for all activities")
.with(
method: :get,
path: '/all/activities.json',
query: {
page: '1',
account_id: '1' },
headers: {'Content-Type' => 'application/json', 'Accept' => 'application/json'} )
.will_respond_with(
status: 422,
headers: {
'Content-Type' => 'application/json; charset=utf-8' },
body: { "error_msg" => "Required parameter missing" } )

22. Consumer Side : Make Request &
Assert
resp = FreshappsActivitiesClient.get_activities(path, query, header)

23. Consumer Side : Make Request &
Assert
resp = FreshappsActivitiesClient.get_activities(path, query, header)
expected_response = { "error_msg" => "Required parameter missing" }
expect(resp.parsed_response.inspect).to eq(expected_response.inspect)

24. Generated Pact File

25. Provider Side : Make Request & Assert
Pact.service_provider 'Freshapps Activities' do
end

26. Provider Side : Make Request & Assert
Pact.service_provider 'Freshapps Activities' do
honours_pact_with 'DevPortal' do
end
end

27. Provider Side : Make Request & Assert
Pact.service_provider 'Freshapps Activities' do
honours_pact_with 'DevPortal' do
pact_uri "../freshapps_devportal/spec/pacts/devportal-freshapps_activities.json"
end
end
end

28. Provider Side : Setup Test Data
Pact.provider_states_for "DevPortal" do
provider_state "all activities without role param" do
end
end
Remember:
Consumer Assumed:
freshapps_activities.given(“
all activities without role
param")

29. Provider Side : Setup Test Data
Remember:
Consumer Assumed:
freshapps_activities.given(“
all activities without role
param")
Pact.provider_states_for "DevPortal" do
provider_state "all activities without role param" do
set_up do
factory :activity do
account_id 1
user_id 1
extension_id 2
version_id 2
activity_type 'Extension'
visibility 1
activity { 'extension_id' => '2', 'name' => 'Sample Extension’}
end
end
end
end

30. Provider Side : Pact Verify Failure

31. Provider Side : Pact Verify Success

32. •My Upcoming Talks:
• WomenWhoCode August Meetup at Freshworks, Aug 19th - on “Docker and
CI”

33. Questions?

34. Thank you!