A better approach for API Testing

Consumer-Driven Contracts

Liran Tal

github.com/lirantal

@liran_tal

Developer Advocate at Snyk

Node.js Security WG

author of Essential Node.js Security

Liran Tal

github.com/lirantal

@liran_tal

Developer Advocate at Snyk

A QA Engineer
walks into a bar...

Orders a beer

A QA Engineer
walks into a bar...

Orders 0 beers

A QA Engineer
walks into a bar...

Orders 999999 beers

A QA Engineer
walks into a bar...

Orders <script>alert('1beer')</script>

A QA Engineer
walks into a bar...

Unit
Testing

E2E
Testing

UA
Testing

Security
Testing

A11ly
Testing

Perf
Testing

Tomcat

MySQL

Monoliths

Build

Test

Deploy

- Simple processes

- One team

- Easy business domain evolution

- Straight-forward testing

Build

Test

Deploy

Build

Test

Deploy

Build

Test

Deploy

Microservices

- Orchestration

- Monitoring

- Configuration

Microservices

in reality

src: https://apigee.com/about/blog/api-technology/microservices-amazon

Microservices

Testing ?

Testing Microservices

Option 1 - Mocks

Build

Test

Deploy

Build

Test

Deploy

GET /stats

Team A

Team B

GET /stats

mock API calls

Testing Microservices

Option 1 - Mocks

Cons

Pros

1. Not reliable

1.   Quick

2.  Cheap

3.  Fast

4.  Deterministic

Testing Microservices

Build

Test

Deploy

GET /stats

Team A

Team B

Option 2 - End-to-End

Team C

Testing Microservices

Cons

Pros

1.  Slow

2. Costly

3. Not scalable

1.  Reliable

Option 2 - End-to-End

Testing Microservices

Option 2 - End-to-End

Slow

Cost

Testing Microservices

Mocks   or   End-to-End...

Are these my only choices?

🤔

GET /stats

data: {

  "movieId": 1001,

  "name": "The Matrix"

  "rating": 10

}

200 OK

What needs to be tested?

The Request

The Response

The Payload

Contract Testing Heaven

Consumer-Driven Contracts

Consumer-Driven Contracts

Integration Testing at Scale

2-Way API Contract Enforcement

API Documentation + Mock

Language SDKs

Contract Testing Framework

Open Source

response: {

  "status": 200

  "body": []

}

Consumer

Contract

Provider

Pact Broker

Collaborate

Consumer-Driven Contracts

Collaborate

Consumer-Driven Contracts

Collaborate

Write

Contract Tests

Consumer-Driven Contracts

Collaborate

Write

Contract Tests

request: {
  "method": "GET",

  "path": "/projects"

},

response: {

  "status": 200

  "body": []

}

Consumer-Driven Contracts

Collaborate

Push Contract to Broker

Write

Contract Tests

Consumer-Driven Contracts

Collaborate

Push Contract to Broker

Write

Contract Tests

Pact Broker

Consumer-Driven Contracts

Collaborate

Push Contract to Broker

Write

Contract Tests

Provider

Implements

Consumer-Driven Contracts

Collaborate

Push Contract to Broker

Write

Contract Tests

Provider

Implements




function amazing_api_endpoint() {
    // incredible logic goes here
    // ...
    // ...
}

Consumer-Driven Contracts

Collaborate

Push Contract to Broker

Write

Contract Tests

Provider

Implements

Download
Contracts

Consumer-Driven Contracts

Collaborate

Push Contract to Broker

Write

Contract Tests

Download
Contracts

Provider

Implements

request: {
  "method": "GET",

  "path": "/projects"

},

response: {

  "status": 200

  "body": []

}

Consumer-Driven Contracts

Collaborate

Push Contract to Broker

Write

Contract Tests

Download
Contracts

Provider

Implements

Run Provider

Contract Tests

Consumer-Driven Contracts

Consumer-Driven Contracts

Collaborate

Push Contract to Broker

Write

Contract Tests

Download
Contracts

Provider

Implements

Run Provider

Contract Tests

request: {
  "method": "GET",

  "path": "/projects"

},

response: {

  "status": 200

  "body": []

}

Users
Service

Get Contracts

Create Contract

Consumer-Driven Contracts

Projects
Service

Validate Contract Not Broken

Use Contract
Mock in Tests

Let's build something...

YouMDB

Serverless-side Rendering

VR

AR

IMIU-AR

Async Flooks

Blockchain

Web: ^2.0.0 technology

YouMDB

Consumer

Movies

Provider

Reviews

YouMDB

YouMDB

Consumer

Movies

Provider

Reviews

data: {

  "movieId": 1001,

  "name": "The Matrix"

  "totalReviews": 10,

  "averageRating": 8

}

GET /movies

?

data: {

  "movieId": 1001,

  "name": "The Matrix"

  "totalReviews": 10,

  "averageRating": 8

}

GET /stats

Consumer Testing

Client > Client Mock > Contract Test > 

HTTP Client

Tests?

Unit Test it ofcourse!

Sinon? Nock?

Import HTTP Client Import Pact      

Declare new mocked provider

Spin it up

Client > Client Mock > Contract Test > 

Define interaction

Expected
request payload

Expected
response payload

Client > Client Mock > Contract Test > 

Trigger the client

Verify expectations

Client > Client Mock > Contract Test > 

Client > Client Mock > Contract Test > 

Consumer Guidelines

1.   Interactions are in test cases

2.  Consider using factories for interactions

3.  Avoid random data in expectations

4.  Match types instead of actual data

5.  Don't tempt into E2E functional tests

response: {

  "status": 200

  "body": []

}

Contract

Client > Client Mock > Contract Test > 

What is a contract?

{

interaction

consumer        provider

request & response

*postel's law

Client > Client Mock > Contract Test > 

What is a contract?

Pact Broker

Pact Contract

Pact Broker

Consumer

Provider

Pact Broker

Pact Broker

  • See The Contract

Pact Broker

  • Consult verification status

  • Built-in API Explorer powered by HAL

  • Verified Version Matrix overview

Provider

Specify the
consumer-provider

Where to download the contract from

Provider > Contract Test

Start verifying

Endpoint to control
states

For each state transition the DB accordingly

Provider > State Management

State Management 🏋️‍♀️

GET /stats

data: {

  "movieId": 1001,

  "name": "The Matrix"

  "rating": 10

}

200 OK

The Request

State Management 🏋️‍♀️

Provider

Reviews

POST /setup

1.  API Service starts...

2. API Service /setup

{
  state:
  "has no stats"
}

GET /stats

200 []

Consumer-Driven Contracts

Collaborate

Push Contract to Broker

Write

Contract Tests

Download
Contracts

Provider

Implements

Run Provider

Contract Tests

Bad Practices

🙅‍♀️

1.   Don't test Provider’s Business Logic

2.  Using Pact as a mock service

3.  Contracts for Public APIs

Benefits of CDC

🤗

1.   Waste reduction

2.  Win both Confidence and Speed

3.  True release independence

Stay Calm
and
Embrace
Consumer-Driven Contracts

Liran Tal

github.com/lirantal

@liran_tal

Developer Advocate at Snyk