Consumer Driven Contracts - A Deep Dive

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

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

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:

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!

• 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

• 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.

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

CDC - Pact File
DevPortal Activities
Request
Response
Consumer Provider

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.

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

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

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

CDC - Sharing Pact Files
Filesystem Cloud Pact BrokerCI Build
Artefact

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

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

has_pact_with "Freshapps Activities" do
end
end

has_pact_with "Freshapps Activities" do
mock_service :freshapps_activities do
port 3005
end
end
end

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'} )

.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" } )

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

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)

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

honours_pact_with 'DevPortal' do
end
end

honours_pact_with 'DevPortal' do
pact_uri "../freshapps_devportal/spec/pacts/devportal-freshapps_activities.json"
end
end
end

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")

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

Provider Side : Pact Verify Failure

Provider Side : Pact Verify Success

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

Consumer Driven Contracts - A Deep Dive

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