Marcin Zajaczkowski
Warsaw, Masovian Voivodeship, Poland
Summary
🤩
RockstarMarcin Zajaczkowski is a seasoned software engineer with 17 years’ experience helping teams deliver business value faster by improving testability, reliability, and continuous delivery. He specializes in TDD and test architecture (Spock, JUnit 5), resilient microservices (Spring Boot, CQRS, Kafka) and CI/CD as code on Kubernetes (ArgoCD, GitLab CI, Jenkins). A hands-on mentor and craft-focused coach, he elevates teams via pairing, code review, ADRs and post-mortems to make automation omnipresent. Marcin is an active open-source contributor to high-profile JVM projects like Spock, Mockito and PIT, where his work improved testing compatibility and async support. He’s particularly adept at bridging developer ergonomics and production-grade reliability—turning tricky async and reactive patterns into maintainable systems. Based in Warsaw, he’s open to opportunities building game-changing internal tools or trailblazing technical products.
17 years of coding experience
Stackoverflow
4,066reputation
498kreached
43answers
17questions
spring-mvc
top-5%
spring
top-5%
dependency-injection
top-5%
code-coverage
top-5%
maven
top-5%
java
top-5%
Github Skills (40)
asynchronous10
test-data10
groovy10
testing10
command-line-interface10
assertj10
java10
tomcat10
javas10
java-libraries10
mutation-testing10
junit10
spock10
test-generator10
gradlew10
Programming languages (29)
Github contributions (5)
SkillPanel/jfairy
Oct 2013 - Mar 2017
Java fake data generator
Role in this project:
Back-end Developer & QA Engineer
Back-end Developer & QA EngineerContributions:55 commits, 9 PRs, 8 pushes in 3 years 5 months
Contributions summary:Marcin primarily contributed to the project by enhancing the test suite and implementing backend code changes. They simplified existing tests, migrated date/time operations to Joda Time, and extracted magic numbers to constants, improving code maintainability and readability. Additionally, they refactored and renamed classes to improve code consistency and project organization. The user's commits also included infrastructure-related changes, such as adding the gradle-wrapper.jar file and upgrading the Gradle version.
fake-data-generatorjavatest-data-generatorgroovyandroid
spockframework/spock
Dec 2015 - Apr 2022
The Enterprise-ready testing and specification framework.
Role in this project:Back-end Developer / Test Automation Engineer
Back-end Developer / Test Automation EngineerContributions:180 reviews, 84 commits, 105 PRs in 6 years 5 months
Contributions summary:Marcin contributed to the Spock Framework, focusing on enhancing the testing capabilities. They modified the `Mock`/`Stub` signatures to improve compatibility and prevent warnings, implemented and maintained default responses for `CompletableFuture` and updated various test scenarios. They also worked on integrating and marking new Spring extensions with beta status. The commits show the user's involvement in improving testing framework and integration with related technologies.
testingjavagroovybdd-style-testing-frameworkspock-framework
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