[Test bash NL] Contract testing in practice with Pact

1. Contract testing
in practice
with Pact
October 15th, 2020 – TestBash Netherlands
@PierreVincent pvincent.io

2. Make sure you have these installed (or similar):
https://www.jetbrains.com/idea/download/
https://www.postman.com/downloads/
https://github.com/PierreVincent/pact-workshop/
Clone the workshop repository:
https://pactflow.io/
Sign-up for free Pactflow account:

3. https://app.sli.do
Questions, thoughts, topics to explore
further…
Code:
#testbash-nl-pact
Please use all throughout the day!

4. Agenda for the day
Contract testing fundamentals
Implementing contract tests with Pact
Scaling contract tests with Pactflow
Designing APIs with contracts
Q&A / Open discussions
Contracts in your architecture
Breaks
Morning
10:30 - 11:00
Lunch
12:30 - 13:30
Afternoon
15:00 - 15:30

5. Pierre Vincent
@PierreVincent
pvincent.io
Head of SRE @
Previously Infra. & SRE Mgr @

6. From this... … to this.

7. Login
Service
User
Service
API
GET /users/pierre
{
"user": "pierre",
"name": "Pierre Vincent",
"role": "publisher"
}
200 OK
How do we
test this?

8. Running in Prod
Tests Pass in
Build
Implement
changes
Deployed in
Prod
User
Service
Login
Service
!
✓ ✓ ✓ ✓
✓
{
...
"role": "editor"
}
{
...
"roles": ["publisher","editor"]
}
Running in Prod
✓ ✓

9. Maybe we should have tested before deploying to
production…?
Tested what
though?

10. Users
Service
Login
Service
IP Check
Service
Token
Gen
Service
Cert/Key
Service
Login
Frontend
We only
wanted to
test this bit!

11. Contract
Login
Service
User
Service
API
Authentication Team Users Team
Consumer Provider

12. What’s in a contract?
Request Headers
HTTP MethodAPI Endpoint
Query Parameters Request Body
Response HeadersStatus Code Response Body
e.g. /api/users e.g. POST
e.g. ?fields=name e.g. Authorization
e.g. Content-Typee.g. 200

13. [docs.pact.io]
PACT Specification
Verification philosophy: Tolerant Reader
Implementation guidelines
Implementations

14. Login
Service
User
Service
A
P
I
Pact
Mock
Server
Authentication Team Users Team
Pact
Consumer
Unit Test
Define
interaction
Trigger
interaction
Generate
Pact
Pact
Provider
Test
Share
Pact
Replay
interaction
Replay &
Verify
Play &
Record

15. Consumer
Provider
Provider State
Request
Expected
Response
Login Service
User Service
Given that user 'pierre' exists
Method GET
Path /users/pierre
Headers
Accept: application/json
Status 200
Headers
Content-Type: application/json
Body
{
"user": "pierre",
"name": "Pierre Vincent",
"role": "publisher"
}
Interaction

16. User
Service
A
P
I
1. Set Provider State
2. Send Request
3. Verify Response
Interaction Verification Test
INSERT INTO users [...]
GET /users/pierre
Accept: application/json
{
"user": "pierre",
...
}
{
"user": "pierre",
...
}
?

17. Sharing Contracts
with Pact Broker
pactflow.io

18. Authentication
Dev Team
Users
Dev Team
CMS
Dev Team
Billing
Dev Team
Pact
Broker
PACT
PACT
PACT
PACT
PACT
PACT
PACT
PACT
PACT
PACT
pactflow.io
✓
✓
✓

19. Dependency
Graphs
Living documentation
by example
✓ Versioning
✓ Tagging
✓ REST Api
Build/Deployment
Pipeline integration
Pact
Broker
pactflow.io

20. Provider pipeline
Implement changes Get Pacts from Broker
Replay & Verify
Interactions
Deploy Service
Build
Deploy to EU
PROD-EU
Get Pacts from Broker
Replay & Verify
Interactions
Stop deployment of
incompatible Provider
Stop introduction of
breaking change
PROD-US
PROD-EU

21. Consumer pipeline
Implement
changes
Generate Pacts
(Build)
Push Pacts to
Broker
Tag Pacts
Each Provider verifies Pacts Deploy Service Tag Pacts
Build
Deploy to EU
HEAD
Stop deployment of
incompatible Consumer
HEAD
PROD-EU

22. Workshop activities

23. Our running example for the workshop
Game
Service
Leaderboard
Service
APIAPI
Play a game
Return result &
current win-rate
Record game result
Return updated
win-rate
Contract

24. POST /play
{
"username": "pierre",
"game": "headsOrTails",
"choice": "heads"
}
Game
Service
API
200 OK
Content-Type: application/json; charset=UTF-8
{
"won": true,
"message": "You won!",
"totalPlays": 120,
"totalWins": 71,
"winRate": 59
}

25. Activity 1
Thinking about API design

26. Game
Service
Leaderboard
Service
API
Record game result:
Game played, User
playing, Won/Lost
Return win-rate:
Games played,
Games won,
Win-Loss Ratio
“Consumer” Teams
- Document what API you need to send
game results
“Provider” Teams
- Document what API you will
implement to receive game results

27. Game
Service
Leaderboard
Service
API
Record game result:
Game played, User
playing, Won/Lost
Return win-rate:
Games played,
Games won,
Win-Loss Ratio
“Consumer” & “Provider” Teams
- Meet to compare your API designs
- Discuss differences and come to agreement on the API interaction
- Have you thought of “unhappy” paths? (API errors)

28. Activity 2
Implementing the
API Contract

29. RecordScore API (or write your own)
Game
Service
Leaderboard
Service
POST /recordScore
{
“username”: “anna”,
“game”: “headOrTails”,
“won”: true
}
{
“gamesPlayed”: 123,
“gamesWon”: 55
}
Request
Response

30. API
Implement API client in Consumer
- In LeaderboardClient.java:
- API endpoint (recordScoreUrl)
- Request Body (RecordScoreRequestBody)
- Response Body (RecordScoreResponseBody)
- In LeaderBoardClientTest.java:
- Implement MockServer unit test
./gradlew test
Run the service unit tests (in game-service dir)
curl -X POST -H "Content-Type: application/json" --data '{"username":
"pierre", "game":"headsortails", "choice": "tails"}'
http://localhost:8080/play
Try your API (curl or Postman)
Game
Service
Why doesn’t this work?

31. API
Creating the Pact
- In LeaderboardClientPactTest.java:
- Complete the PACT definition (RequestResponsePact)
- Update expected response (expectedResponse)
- Update expected request (client.recordScore)
./gradlew test
Run the pact test (in game-service dir)
cat build/pacts/game-service-leaderboard-service.json
Find the generated PACT
Contract
Does the contract match
what you defined?

32. Leaderboard
Service
API
Implement the Provider API
- In ScoreController.java:
- API endpoint (@PostMapping)
- Request Body (RecordScoreRequestBody)
- Response Body (RecordScoreResponseBody)
./gradlew run
Run the service (in leaderboard-service dir)
curl -X POST -H "Content-Type: application/json" --data
'YOUR_JSON_PAYLOAD' http://localhost:8081/your/api/endpoint
Try your API (curl of Postman)

33. Verifying the pact
- Copy the generated PACT file (game-service/build/pacts/*.json)
to the Provider test resources (leaderboard-service/pacts)
./gradlew pactVerify
Run the verification test (in leaderboard-service dir)
Contract
✓

34. @PierreVincent
Thank you!
Pierre Vincent
@PierreVincent
pvincent.io