The document describes a scenario where a change to a backend service broke a dependent service. It introduces the concept of consumer-driven contract testing (Pact tests) as a way to prevent such issues. Pact tests involve the consumer service making assertions about the responses expected from the provider service by generating a contract. This contract is shared and verified by the provider service to ensure compatibility when changes are made. The document provides an example of setting up Pact tests between a DevPortal and Freshapps Activities service to validate responses and prevent breakages when one service evolves.

1. Pact Tests
(Consumer Driven Contracts)

2. Based on a true (truly imaginary?) story!
Alice
• our main character in the story
• Senior Dev in FreshMock.com
• Owns a “Subscription Service”
• Friday the 13th!

3. What happened on Friday the 13th?
● “CustomerInfo Service”’s change
● Updates a property in the response object
● Changes “customer” (which returns a list of customers) to
“customers” (Grammatically correct though! :( )
● BUT this one letter change BROKE the “Subscription Service”

4. Here comes the bigger question…
Why didn't our tests
catch this??

5. So how do you test?
● Mock the dependencies
Subscription Service Mock CustomerInfo Service
Request
Response

6. Unit Tests
● Similarly the “CustomerInfo Service”, has a mock client for
“Subscription Service”
● It DID fail!
● But then “I updated my test because I know this is an expected
failure! ”

7. Unit Tests
● Why do we still do it?
• Fast
• Easy to setup
• No Flakiness!
• Ensures functionality of a specific microservice

8. Integration Tests
Subscription Service CustomerInfo Service
Request
Response

9. Integration Tests
● Slower
● Set up time (“Stack Setup!”)
● More flakiness
● More infrastructure!
● End up doing an E2E tests

10. Other types of Tests
•End-to-End Tests
•Manual Tests
•Again,
• Stack Setup!
• Slower (E2E tests)
• More flakiness
• Not failing fast!

11. Solution?
Is there a better way to identify
these kind of issues?

13. Pact Tests
• Also called “Contract Tests”
• Consumer Driven Contract Tests (CDC Tests)
• Tool Used: Pact
• A Contract is a collection of agreements between a client (Consumer)
and an API (Provider) that describes the interactions that can take
place between them.

14. Pact Tests? What are these?
Subscription Service CustomerInfo Service
Request
Response
Consumer Provider

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

16. Is it just another Mock HTTP Server?
Subscription Service CustomerInfo Service
Request
Response
Consumer Provider

17. The 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.

18. Pact Tests:Provider Side
CustomerInfo Service
Replay each HTTP Request
Get real HTTP Response
Provider
Pact File Compares real and
mock responses

19. Provider States
• Get billing address of customer
with id=777
Subscription Service CustomerInfo Service
Request
Response
Consumer Provider
Request
Response
?

20. state: cust_id=777 @ DB
Provider States
• Get billing address of customer
with id=777
Subscription Service CustomerInfo Service
Request
Response
Consumer Provider
Request
Response
state: cust_id=777 @ DB
state: cust_id=777 @ DB

21. Sharing Pact Files
Filesystem Cloud Pact BrokerCI Build
Artefact

22. Sharing Pact Files - Pact Broker
• Pact Broker - a repo for storing pacts
• Auto-generated documentation
• The ability to tag a Pact (i.e. “prod") -
versioning pacts
• Network Graph

23. Sharing Pact Files - Pact Broker

24. Automating Pact Tests
• When a new Pact is published, how does the Provider get notified?
Manual Trigger Pact Broker
Webhook
Swagger Validator

25. Advantages
•Eliminates Wrong Assumptions
•Enables communication
•Very less setup time!
•No extra infrastructure
•Fast in Execution
•Fails Fast
•No flakiness!
•Easy to debug

26. DEMO
Freshapps DevPortal Freshapps Activities
Request
Response
Consumer Provider

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

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

29. 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

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

31. 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'} )

32. 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" } )

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

34. 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)

35. Generated Pact File
{
"consumer": {
"name": "DevPortal"
},
"provider": {
"name": "Freshapps Activities"
},
"interactions": [
{
"description": "a request for all activities",
"provider_state": "all activities without role param",
"request": {
"method": "get",
"path": "/all/activities.json",
"query": "page=1&account_id=1",
"headers": {
"Content-Type": "application/json",
"Accept": "application/json"
}
},
"response": {
"status": 422,
"headers": {
"Content-Type": "application/json; charset=utf-8"
},
"body": {
"error_msg": "Required parameter missing"
}
}
}
],
"metadata": {
"pactSpecificationVersion": "1.0.0"
}
}

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

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

38. 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

39. 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")

40. Provider Side : Setup Test Data
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
Remember:
Consumer Assumed:
freshapps_activities.given(“
all activities without role
param")

41. Provider Side : Pact Verify Failure

42. Provider Side : Pact Verify Success

43. pact.io
• Working examples and documentations available at pact.io
• Supports: Ruby, Java, .NET
• Beta: JS,Python, Swift, Go
• https://groups.google.com/forum/#!forum/pact-support
• https://gitter.im/realestate-com-au/pact
• Other Similar Tools:
• Pacto (by Thoughtworks - but not maintained though.)

44. References
● To know about Consumer Driven Contract: https://
martinfowler.com/articles/consumerDrivenContracts.html
● https://www.thoughtworks.com/radar/techniques/
consumer-driven-contract-testing

45. And… What happened to Alice?
Oh yea! She implemented “Pact Tests”
and
lived happily ever-after!!

46. Questions

47. Thank You!