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Fake it until you `make it`
API Integration testing of embedded projects
with Testcontainers and WireMock
Oleg Nenashev,
WireMock Inc
QA&Test 2023
Bilbao
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`make it` ?
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Integration testing?
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● Multiple technology stacks
and toolchains
● Many teams involved
● Sacred knowledge
● [Almost] always too late
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Outline
● Intro to API integration testing
● Testcontainers and WireMock
● Using them together
● And examples! C/C++, Golang, Rust
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bit.ly/qatest2023_wiremock
Disclaimer: This is a talk about “WireMock AND
Testcontainers”, not “VERSUS” ir “OR”. Your mileage may vary
These slides:
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> whoami
@oleg_nenashev
oleg-nenashev
Dr. Nenashev / Mr. Jenkins
Developer tools hacker
Community builder & DevRel consultant
#RussiansAgainstPutin #StandWithUkraine
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@oleg_nenashev
oleg-nenashev
> whoami --automotive --embedded --hardware
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CloudBees Embedded &
Automotive Day
in Stuttgart
LibreCores CI
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Do you already use
container technologies in test
automation?
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Also: 2016 - Pini Reznik, Containers and test
automation & More & More
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Why containers?
● Configuration
Management
● Fast provisioning
● Clean environments
● Disposability
● Clustering
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Docker in Embedded
Prototypes, Dev Tools Test Infrastructures, CI/CD
Docker Swarm Cluster on Raspberry Pi
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Even simulator
is not always an
option
http://blogs.synopsys.com/breakingthethreelaws
2014/04/the-secret-ninja-fu-for-higher-performa
e-prototype-operation/
HAPS S96
Guess the price…
Your device
prototype is
here
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Docker
● Popular container engine
● Developer-friendly
● Huge ecosystem
● DockerHub and Container Registries
● Docker Compose – multi-container apps
● Universal image format (OCI)
https://www.docker.com/
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Do your projects have APIs?
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APIs are essential for Integration Testing
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GROWTH IN WEB APIS SINCE 2005
Over 90% of developers
use APIs.
Skyrocket growth of APIs
JANUARY
2006
JANUARY
2008
JANUARY
2010
JANUARY
2012
JANUARY
2014
JANUARY
2016
JANUARY
2018
MONTH
The growth over time of the Programmable Web API
API directory to more than 22,000 entries
22000
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
TOTAL API COUNT
Programmable Web
* Gartner Hype Cycle for APIs, 2022
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APIs
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Source: https://medium.com/10-minutes-qa-story/api-testing-from-scratch-api-anatomy-f220856ce9b3
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APIs are essential for
Integration and Integration Testing
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Ways to do API integration testing
1. Testing against Production/Staging servers
2. Testing against a simplified/containerized
instance (e.g. Testcontainers)
3. Mocking at the API provider level (e.g.
WireMock)
4. Mocking at the code level
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Slow
Fast
Accu-
rate
Nope
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Ways to do API integration testing
1. Testing against Production/Staging servers
2. Testing against a simplified/containerized
instance (e.g. Testcontainers)
3. Mocking at the API provider level (e.g.
WireMock)
4. Mocking at the code level
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Slow
Fast
Nope
Accu-
rate
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Build
Unit tests
Publish Reports
Integration tests
Publish Reports
WAS
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Build
Unit tests
Publish Reports
Integration tests
Publish Reports
NOW
“Shift Left”
Fast integrations
tests are critical
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Staging & QA
Tests
Build
Integration tests
Build
Tests
Gaining confidence in you software
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Shifting ITs left
with Testcontainers and WireMock
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Ways to do API integration testing
1. Testing against Production/Staging servers
2. Testing against a simplified/containerized
instance (e.g. Testcontainers)
3. Mocking at the API provider level (e.g.
WireMock)
4. Mocking at the code level
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Slow
Fast
Accu-
rate
Nope
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SDKs
C/C++ testcontainers.org
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Example
- JUnit 5
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Containers are not always slow!
● On-demand image build
● Caching Docker image builds
● Suspending containers between tests
● Graceful termination
○ github.com/testcontainers/moby-ryuk
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testcontainers.org
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https://wiremock.org
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Ways to do API integration testing
1. Testing against Production/Staging servers
2. Testing against a simplified/containerized
instance (e.g. Testcontainers)
3. Mocking at the API provider level (e.g.
WireMock)
4. Mocking at the code level
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Slow
Fast
Accu-
rate
Nope
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WireMock 101
WireMock is a tool for building mock APIs
Created in 2011 as a Java test library and CLI
Available beyond Java, inc Rust or Golang
You can can:
● Create stable development environments
● Isolate yourself from flakey 3rd parties
● Simulate APIs that don't exist yet
wiremock.org
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wiremock.org/docs/stubbing
IF (request_url)
THEN (response) *
* it gets MUCH more complex
WireMock Config JSON:
Client
library response
request
Client App Mock API Server
HTTP/2
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Breaking down
JSON files
Using WireMock Cloud
app.wiremock.cloud
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WireMock in Java
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wiremock.org/docs/stubbing
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WireMock Ecosystem & Features
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wiremock.org/docs
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WireMock Ecosystem & Features
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wiremock.org/docs
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Example -
WireMock for Rust
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docs.rs/wiremock/latest/wiremock
LukeMathWalker/wiremock-rs
Note: WireMock for Rust is maintained
outside the WireMock GitHub organization
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Comparison [1/2]
1. Testing against Production/Staging servers
2. Testing against a simplified/containerized
instance (e.g. Testcontainers)
3. Mocking at the API provider level (e.g.
WireMock)
4. Mocking at the code level
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Slow
Fast
Nope
Accu-
rate
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WireMock has an official Testcontainers module!
testcontainers.com/modules/wiremock
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Example
- JUnit 5
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WireMock as a Proxy
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Tests
Real API Provider
OR
● Fault injection
● Recording
● Protocol Verification
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How about
embedded?
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IEEE Spectrum
Research among
members
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https://spectrum.ieee.org/top-progra
mming-languages-2021
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jetbrains.com/lp/
devecosystem-2021/embedded/
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Supported by WireMock and Testcontainers
C/C++ Shared Lib Interface
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Testcontainers for C/C++
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Started by the WireMock Team in
September 2023
We have Embedded/Automotive
customers and users who need it
Based on Testcontainers or Go
WireMock module
github.com/testcontainers/testcontainers-c
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Example - WireMock
with C code
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github.com/testcontainers/testcontain
ers-c/tree/main/examples/wiremock
● Testcontainers C is an
experimental project
● Feedback is welcome!
● See more examples in
the repository: CppUnit,
OpenSCADA, etc.
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WireMock for
Google Test / C++
github.com/testcontainers/te
stcontainers-c/tree/main/de
mo/google-test
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And then a test!
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github.com/testcontainers/testcontainers-c/tree/main/demo/google-test
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Demo time! Integration Testing
With WireMock
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Takeaways
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● Shift left your integration testing
● Mocking APIs and services, reducing
external dependencies, containers
● There are tools for that, including
WireMock and Testcontainers
● WireMock and Testcontainers co-exist well
● They work for embedded use-cases!
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Choosing a
right tool * **
* Your mileage may vary
** You will often need both and that’s OK!
Need database or complex
dynamic environment?
Yes
Server implementation is ready?
Is it containerized and lightweight?
Can you [easily] transfer the
system to the required state
in test?
No
No
No
No
Yes
Yes
Yes
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Get Started
wiremock.org/docs/solutions/embedded
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THANK YOU
Contacts:
E-mail: [email protected]
GitHub: oleg-nenashev
Twitter: @oleg_nenashev
QUESTIONS?
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WireMock Cloud by WireMock Inc.
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● Small startup
● WireMock creator is a
co-founder of the Inc.
● WireMock Cloud - SaaS for
end-to-end API mocking
● Private beta: K8s Edition for
managed / on-premises
wiremock.io
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Credits to
● All WireMock contributors
● WireMock Inc. Team
● All Testcontainers contributors
and AtomicJar folks
● All FOSS contributors
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