Software Development, Testing & Open Source

Glass sphere resting on wet pebbles at the shoreline, reflecting a pier and sunset, symbolizing a shift in perspective and bringing clarity to complex testing practices.

March 11, 2026

From anti-pattern to clarity

The any() matcher is deprecated. But migration is easier than you think – and leads to better tests.

The image shows a person untangling a complicated thought in order to find a solution to a problem.

March 4, 2026

Better than withConsecutive()

I explain how PHPUnit 13's parameter set matchers finally solve the problem that made upgrading to PHPUnit 10 such a challenge.

The image shows a close-up of printed financial data on paper, with multiple vertical columns of numbers in black, green, and red ink representing values such as prices or changes. A metallic pen lies diagonally across the sheet, suggesting analysis or review of the numerical information.

February 25, 2026

Replay Testing

Replay Testing leverages the memory of your event sourcing system to test new versions with real history and shows which oracles truly inspire confidence in your changes.

The image illustrates that valuable insights can be gained from recorded events through skilful processing and analysis, a metaphor for the value of event sourcing and automated testing in software development.

February 20, 2026

From Events to Insights

Event Storming, DDD, CQRS, and Event Sourcing are intertwined: the tests not only check the events, but also become living documentation and a bridge between technical expertise and code.

February 11, 2026

How my understanding of software changed

A classic database only stores the "now" and forgets history. In this article, I describe my journey to DDD and event sourcing and explain why we need to learn to model time itself.

February 4, 2026

Data Provider or Properties?

One test, hundreds of inputs, and an automatic edge case search. But property-based testing has a hidden pitfall that many overlook.

The image shows a hand against a dark background, presenting a glowing light form that is drawn half like a brain, half like a light bulb. The scene conveys focused clarity and symbolises small inputs with great insight – fitting for shrinking in property-based testing.

January 28, 2026

Smaller input, greater insight

Shrinking is the unsung hero of property-based testing. I show you how it helps to make inevitable errors understandable.

January 21, 2026

Property-Based Testing

We only test what we think of. That is precisely what can become a problem.

The image shows a colourful, chalky network of dots and connections on a black background. It is a playful visualisation of distributed, loosely coupled communities and thus fits perfectly as the mood for an article about the Fediverse.

January 18, 2026

Open Source, Open Feeds: Mastodon and PeerTube as online spaces for the PHP community

With phpc.social and phpc.tv, the PHP community is building its own donation-funded online spaces in the Fediverse – free from algorithms and fascist tech bros.

The image shows several interlocking gears in white and yellow on a dark board surface. A hand is adding to or highlighting one of the yellow gears. This hand can be interpreted as a symbol of the developer, who deliberately inserts new, type-safe components into an existing system without disrupting the mechanism.

January 14, 2026

Type-Safe Collections

Does PHP really need generics? A controversial thesis with a practical solution.

The image depicts a symbolic scene that represents cooperation and team spirit. The focus is on several hands arranged in a circle from above, working together to bring wooden puzzle pieces together. The hands belong to different people wearing different clothes. Some light-coloured shirts and grey sleeves are visible. The scene takes place on a green meadow, conveying a sense of naturalness and openness. The light-coloured puzzle pieces represent the individual components that must be put together to form a larger whole.

January 7, 2026

How PHP and its ecosystem test each other

PHP tests Laravel, Symfony, PHPUnit, and more every night. PHPUnit tests PHP. This is Open Source collaboration at work.

This image depicts a woman holding a white theatrical mask up to her face against a dramatic, dark background. A bold red panel is visible on the left, and there is ambient stage lighting in the background, consisting of blue and white orbs. Her eyes peer over the mask, suggesting a moment of self-examination or realisation, with an expression of curiosity and slight concern. The theatrical setting and professional staging emphasise the performative nature of the moment.

December 31, 2025

The Stub/Mock Intervention

Self-sabotaging mock objects? With PHPUnit 12.5, that's a thing of the past because the test runner now asks the right question: Do you really need a mock object, or would a test stub suffice?

This festive holiday image showcases a beautifully illuminated Christmas tree rendered as an artistic composition of soft, out-of-focus bokeh lights against a deep navy blue night sky. The tree is constructed entirely from overlapping, translucent circular orbs of light, creating a dreamy, impressionistic effect.

December 24, 2025

A festive break

I take a break from my weekly articles and invite you to a free online event where I will present the latest improvements to PHPUnit.

The image shows an aircraft flight recorder, commonly known as a "black box", resting on the seabed under water. The cylindrical orange device is slightly rusted and mounted on a base plate, with a rectangular attached unit behind it. A large white label on the cylinder reads "FLIGHT RECORDER DO NOT OPEN".

December 17, 2025

A flight recorder for your code

Your PHP project has no tests and an upgrade is pending? The classic dilemma: to introduce tests, you have to change code – to change code, you need tests. How can you break this cycle? With characterisation tests.

The image shows two hands that seem to be forming a glowing light that appears magical. The person is wearing several rings and bracelets and has their arm tucked into a purple jumper. In the foreground is a table covered with a dark cloth, on which lie candles, coins, chains and a small bottle containing a blue-green liquid. The warmly lit scene evokes a spiritual or mystical atmosphere, reminiscent of a ritual or fortune telling.

December 10, 2025

Seeing the Truth: Test Oracles

Your tests are successful. But are they really? Without a suitable test oracle, you will never know.

This image illustrates the contrast between technical motivation, represented by flowing, dynamic data streams, and domain motivation, represented by solid, stable foundational concepts. This visual metaphor illustrates the main point that DTOs facilitate the movement of data between layers, while value objects represent unchangeable domain concepts that form the basis of business logic. The layered architecture also illustrates how these objects are used in different contexts: technical boundaries versus core business logic. It emphasises the stability and predictability that immutability brings to testing practices.

December 3, 2025

Testing with DTOs and Value Objects

Know the differences between data transfer objects and value objects and understand why immutability helps with testing.

The image shows a variety of colourful game pieces (such as those often used in board games) arranged on a surface with lines drawn on it connecting the pieces to each other. The pieces are in different colours (e.g. red, yellow, blue, green, purple, black) and stand at the intersections of a schematic network. The lines indicate that the pieces have relationships with or are connected to each other. The image thus visualises a network or web of relationships between different entities, which is often used to illustrate concepts such as networks, social relationships, teamwork or dependencies.

November 28, 2025

Testing with(out) dependencies

Why distinguishing between test stubs and mock objects in PHPUnit significantly improves the quality and readability of tests.

This image shows a stylised representation of a DNA double helix, with a single section highlighted. The DNA strands are shown in blue, while a short section of the base pairs and the associated connections glow red. The imagery communicates a mutation or targeted change at the molecular level, as applied in genetic analysis, mutation testing or biotechnological processing. The focused area could symbolise a mutation, repair or targeted intervention, as used in genetic research.

November 19, 2025

Path Coverage or Mutation Testing?

How thoroughly do your tests cover the code, and how reliably do they detect real errors? I show you how to find out.

The image shows a row of electrical circuit breakers with wooden letter blocks placed on top of each breaker. The blocks spell out the phrase "BLACKOUT." In front of the circuit breakers, there is a lit candle, symbolizing the situation of a power outage or blackout where electric power is unavailable and people rely on candles for light. The setting appears to be indoors, and the candle's flame provides a warm light illuminating the breakers and the surrounding area. The image visually represents the concept of losing electrical power with the word "blackout" and the candlelight.

November 11, 2025

Open Source Blackout

Are you prepared for a world in which your projects freeze, deployments stall, and tech giants can no longer rely on free community-run infrastructure?

The picture shows a beautiful mountain landscape in the morning or evening light. In the foreground, you can see several dark, partly snow-covered ridges, while in the background, gently rolling hills and mountains disappear into the distance on several levels. The scene is shrouded in mist or haze, which enhances the colour gradient from violet to pink to bright yellow and finally blue in the sky. At the bottom right edge, a single person stands on a ridge with a walking stick, giving the image a particularly calm and impressive atmosphere.

November 5, 2025

More control, less friction: What's new in PHPUnit 12.4?

Discover how PHPUnit 12.4 helps you get there with less friction and more insight.

This image shows a modern graphic collage depicting stylised hands holding or passing several light bulbs. The light bulbs symbolise ideas and innovations, with their yellow colour immediately catching the eye and conveying a positive, creative impression.

October 29, 2025

Modern PHP Development

Modern PHP development combines proven principles with the latest tools. It brings together documentation, quality, automation, and AI.

The image shows a wooden staircase leading through dunes to the beach, running towards a sunrise or sunset. The years from 2026 to 2035 are painted large and white on the individual steps, as if symbolising the path to the future. At the end of the staircase, where the light is strongest, the journey seems to lead into the coming years, while the wide sky and calm sea in the background convey a peaceful, expansive mood.

October 22, 2025

A look ahead to 2035

I discuss key issues for the future relating to ethics, digital sovereignty, Open Source, and web standards.

The picture shows a light bulb lying on a wooden surface. The light bulb is lit and creates a warm atmosphere. Right next to the light bulb is a small pile of various old metal keys. The interplay between the glowing light bulb and the keys symbolically conveys the idea that ideas (light bulb) can be the key (bunch of keys) to new possibilities or solutions.

October 15, 2025

PHPUnit features that surprise even professionals

Discover the hidden capabilities of PHPUnit and learn how to get the most out of your tests with clever features.

The image shows the interior of a vehicle with a futuristic-looking control panel consisting of several orange and green seven-segment displays arranged one above the other, showing the date and time, flanked by metal plates, switches, cables and connectors, creating the impression of a time travel console.

October 7, 2025

From AmigaBASIC to AI

A personal journey from my first lines of BASIC on the Amiga to the question of how AI will shape the next generation of developers.

The image shows several people working together to assemble a puzzle made up of yellow pieces that form the shape of a light bulb. The light bulb typically symbolises an idea or innovation. The scene takes place on a wooden table, which also holds a cup of coffee, a glass of water, an open laptop and some documents. The people's hands are visible as they fit the puzzle pieces together, illustrating collaboration and teamwork.

September 1, 2025

Innovation through collaboration: The highlights of PHPUnit 12.3

Discover how collaboration with real-world developers has shaped the latest advancements in PHPUnit 12.3.

Workspace with various tools that are often used for precise manual work, model making or handicrafts

June 16, 2025

Psalm or PHPStan?

Psalm or PHPStan: which tool is the better choice for code analysis? Or is it worth combining both tools for maximum code quality?

A person wearing a backpack stands on a rocky ledge overlooking a range of green mountains under a partly cloudy blue sky.

June 8, 2025

30 Years of PHP, 25 Years of PHPUnit

I look back on 30 years of open source innovations.

Collaborative prioritisation of quality goals with LASR

May 10, 2025

ComoCamp 2025

I am thrilled by the inspiring workshops, exciting open space sessions and the uniquely open, collaborative atmosphere of ComoCamp.

August 25, 2024

SoCraTes 2024

SoCraTes has enriched and motivated me in a lasting way through inspiring discussions, exciting sessions on topics such as PHP, software testing, security and open-source funding, as well as the special, collaborative atmosphere.

Tool wall on which a variety of hand tools are neatly arranged

June 25, 2024

PHP_CodeSniffer or PHP-CS-Fixer?

Should PHP_CodeSniffer or PHP-CS-Fixer be used to get code "in shape"? Should both tools even be used together?

A man is sitting on a dune covered with dry grass. He appears pensive or perhaps even sad, as he rests his head on his arm with one hand while looking down.

March 22, 2024

PCOV or Xdebug?

Should you use PCOV or Xdebug to collect code coverage data? I give a personal answer.

The image shows a panoramic view of a harbour with a train on an elevated railway bridge in the foreground. On the left is a modern building with a striking glass façade, which is the Elbphilharmonie concert hall in Hamburg. In the background, several ships and cranes can be seen, indicating port activity. The weather is cloudy but bright, suggesting late afternoon or early evening. The scene appears both calm and industrial.

March 11, 2024

PHPUnit Code Sprint: March 2024

I recollect my experience at the PHPUnit project's most recent code sprint.

The image shows a yellow diamond-shaped traffic sign with the black inscription "DEAD END". It is located in an urban environment, in front of a building with large windows and metal bars. In the background, there are other buildings with typical metal external staircases, as are often found in some neighbourhoods. The sign indicates that the road ends at this point and that it is not possible to drive through.

November 28, 2022

PHP 7: Security Support Ends. Now what?

Security support for PHP 7 has ended. What does this mean for you?

The image shows a cork notice board with a yellow sticky note attached to it with two red pins. The note has a stylised light bulb drawn on it, representing an idea or a flash of inspiration. The light bulb is surrounded by short lines symbolising rays of light, reinforcing the image of creative inspiration or a brainwave.

April 4, 2022

How I manage test fixture

I reflect on why I no longer write setUp() methods.

The image shows two people starting on a running track. In the foreground, a person in a red sports outfit is seen in the starting position for a sprint, ready to run. In the background, another person is also in the starting position. The image conveys a sporty and competitive moment on an outdoor athletics track in daylight, surrounded by trees and buildings.

August 2, 2021

Ready Or Not, Here It Comes

Is your software ready for PHP 8.1? Now is the time to find out.

A sign reading "Private Property No Entry" stands in front of a large modern house with a wooden deck and glass railings in the background.

April 21, 2021

Do not mock what you do not own

If you use abstractions you don't own, testing may be difficult.

The image shows a glass surface covered with fine water droplets or condensation. A large question mark has been painted or wiped onto this fogged-up glass. The background appears yellowish to greenish and blurred, so that the question mark clearly stands out as the central motif.

October 8, 2020

Caching makes everything faster. Right?

While working on PHPUnit, I encountered an interesting problem.

The image shows two chess pieces on a light, almost white background. The central piece, a black king, stands upright. Next to it lies another king – presumably white – on its side, apparently defeated. The scene appears minimalistic and focuses exclusively on this symbolic moment, which is often interpreted as representing victory and defeat.

July 6, 2020

Failing IT Projects

I explain how we can learn from failed IT projects.

The image shows an analogue wall clock with a yellow frame hanging on a white wall. The time is approximately 6:50 p.m. The clock face has a simple design and the background of the clock and the wall are white, giving the image a very minimalist look. There is a lot of empty space on the left, while the clock is located on the right side of the image.

June 5, 2020

Who wound the clock?

I explain why PHPUnit no longer looks at the clock.

The image shows a wooden sign with the word "CLOSED" written on it. The sign is photographed at an angle and, thanks to its warm, brownish colouring, blurriness and strong grain, has a particularly atmospheric and nostalgic feel. It is reminiscent of a photograph taken in a small, cosy shop or café at closing time.

February 21, 2020

PHPUnit: A Security Risk?

The long story of a security problem that should not have been one.

The image depicts a tranquil seascape at sunset or sunrise. The water's surface reflects the warm colours of the sky, which glows in shades of orange, yellow, blue and violet. Several birds can be seen flying in the sky, creating a peaceful and relaxed atmosphere. The silhouettes of the birds stand out clearly against the colourful horizon, emphasising the vastness and tranquillity of the scene. In the background, a dark headland or coastline can be seen, completing the picture.

February 7, 2020

Migrating to PHPUnit 9

In the tension between backward compatibility and progress, a good developer experience must not be neglected.

The image shows a concrete wall with a rough surface and visible horizontal lines and joints. Shadows fall on it, forming patterns, presumably from plants or leaves. The shadows create an interesting interplay of light and dark, giving the image a calm, natural atmosphere.

February 1, 2019

Blast from the Past

Package managers are worthwhile targets, even if no one uses them anymore. Background information on the breach of the PEAR infrastructure of the PHP project.