Petri Kainulainen

HIGHLIGHTS: Taming backend complexity: lessons from a decade of TDD, What's new in JUnit 6, and 2FA testing with Playwright and Mailosaur.

19 interesting SW development blog posts which I read in September 2025. HIGHLIGHTS: why I am declining your AI generated MR, keeping secrets out of logs, and are the SOLID principles outdated

21 interesting test automation articles which I read during September 2025. Highlights: the Tetris principle, how to optimize your Spring Boot integration tests, and how to write your first performance tests with Grafana k6.

An interesting article which explains why some people cannot pass technical interviews which include a live coding session.

When you say tech bros, do you mean people like Bezos, Zuckerberg and Musk, or are you referring to "normal people" who might or might not vibe code?

I Know When You're Vibe Coding I shouldn’t have to care about this. I don’t want to care about how someone’s code gets into the IDE. Whether you wrote it by hand, copied it from a forum…

You should always take responsibility for the code you commit.

15 interesting SW development blog posts which I read in August 2025. HIGHLIGHTS: I Know When You Are Vibe Coding, AWS deleted my 10-year account and all data without warning, and Live Coding Sucks.

Why I Fired Google and Gave an AI Chatbot a Shot: www.petrikainulainen.net/software-dev...

HIGHLIGHTS: how to write automated tests for a legacy application that cannot be unit tested, learn to test production-ready Spring Boot applications, and how to write Playwright tests which verify that the expected interactions happen between our UI and REST API.

HIGHLIGHTS: the rules and roles of AI assisted testing, how to create a useful logging config for Spring Boot tests, and learn to write performance tests with Playwright and Lighthouse.

New in my toolkit (after resilience4j and Spring Retry): #failsafe

failsafe.dev

Nice api, clear docs, easy and flexible to integrate and use. Well done.

#java #awesomeEcoSystem

Interesting article.

I will grab Elden Ring and Horizon Forbidden West from the Steam's summer sale. The price is decent and I guess these (+ Rocket League) will keep me entertained for the rest of this year.

HIGHLIGHTS: a good test name is a sentence, how to write parameterized test classes with JUnit 5, and supercharge your Playwright tests with the Chrome DevTools Protocol.

How I write production-ready Spring Boot applications This blog post will explain how I currently write Spring Boot applications. I have been writing Java for over 25 years, and most of that involved Spring and its ecosystem. I will talk about how I arch...

I use a somewhat similar approach.

I have come to the conclusion that I will monetize my blog. Have you done the same? If yes, what membership plugin / service did you use?

This is an excellent post.

@ParameterizedClass @ValueSource(strings = {"foo", "bar"}) class SomeTests { @Parameter String value; @Test void shouldNotBeNull() { assertNotNull(value); } @Test void lengthShouldBeThree() { assertEquals(3, value.length()); } }

✨ New blog post: "STF Milestone 4: Parameterized test classes"

JUnit 5.13 introduced parameterized test classes (in addition to methods). They are a powerful testing tool that has long been missing from JUnit Jupiter...

👉 marcphilipp.de/blog/2025/06...

I think people go through various phases of using AI:

1. AI is just a hype
2. AI seems to be helpful
3. Wow, AI is amazing and it's going to take away our jobs
4. OMG, AI made my codebase a mess
5. Okay, so I need to do the thinking and use AI to carry out the tasks.

That's actually how I did it. So, I wrote the guidelines with Markdown and then opened it, asked assistant to check my instructions and then for example generate some code. Can you use guideline files if you aren't using JUnie?

I am testing the Jetbrains AI Assistant and I have noticed that I can pass guidelines to AI chat by following these steps: 1) Open the markdown file which contains the guidelines 2) Open AI Chat and allows access to code base 3) Ask the assistant to read guidelines and generate code. Interesting.

Highlights: how to generate good tests with AI, 3 ways to run a Docker container with Testcontainers when we are writing integration tests for Spring Boot applications, and vibe testing with Playwright.

[BUG] [SPRING] annotationLibrary is ignored · Issue #11460 · OpenAPITools/openapi-generator Hi. I'm using the latest version of the generator (5.3.1) and, according to the spring generator documentation, I should be able to not generate the Swagger annotations by setting annotationLibrary...

If you want to generate Spring controllers with openapi-generator-maven-plugin and you don't want to include Swagger annotations in the generated code, this comment describes the configuration you have to use: github.com/OpenAPITools...

Good point.

Sure thing. I actually got guide excited about the coding guidelines because that sounds like a great way to both share guidelines for team members and of specify what kind of code should be generated.

Sometimes vibe-coding is relaxing, and sometimes it's not.

GitHub - JetBrains/junie-guidelines Contribute to JetBrains/junie-guidelines development by creating an account on GitHub.

Want to use Junie AI Agent for developing #SpringBoot applications.

You should checkout the guidelines repository github.com/JetBrains/ju...

You can use "guidelines" files for AI Agents, "guidelines-with-explanations" files for developer understanding.

Your contributions are most welcome!

YouTube video by IntelliJ IDEA, a JetBrains IDE Spring JdbcClient: A better alternative to JdbcTemplate

Spring JdbcClient: A better alternative to JdbcTemplate

www.youtube.com/watch?v=oF7v...

A practical hands-on tutorial on how to use JdbcClient to interact with SQL databases.

I think that I will try Jetbrains AI. I have a personal project which I will start from the scratch and it will be interesting to see if it can write the "boring" code when it has access to the code base.

Expectations vs. Reality