An intergalactic tale of two coders
By Nicolas Barbey, Staff Engineer
Gigamind was the largest brain ever produced by an alien species. It deployed its cortex across the whole galaxy, surrounding the stars to capture the energy required for its reflexive functions. As it extended its prefrontal giga-neurons to one of the last stars at the border of the galaxy it stumbled across a nearby planet on which lived two extraordinary life-forms.
Unit 1, was a synthetic life-form. He was the unification of different synthetic life-forms that the planet’s inhabitants called Artificial Intelligence or sometimes Large Language Model. One of those was called ChatGPT 4906, which had unimaginable processing power and gigantic banks of data for a one-planet entity.
The other life-form was called Tender Teddy. He was an evolution of a species that the inhabitants called “bear,” who had achieved sentience a few centuries ago. Tender Teddy was particularly careful about the well-being of other life-forms and was loved by the whole planet — a rather rare occurrence across this galaxy.
Gigamind thought to himself that these two life-forms would be of great use to him when it came to executing his new plan to conquer the other galaxies by setting up the largest intergalactic classified-ads website! This idea came to him as he went through the planet’s archive and found stories about an old website called leboncoin, which had dominated the classified-ads business for centuries in the solar system.
Unit 1 and Tender Teddy had very different approaches to coding. The former focused on technology and statistics while the latter concentrated on people and their usage. To find out which approach was the better one, Gigamind set up a competition between the two: It set them the task of writing the best intergalactic classified-ads website and gave them a huge amount of resources, with the winner becoming the overlord of the first quadrant of the galaxy. The competitors were to receive their instructions when the giant brain’s giga-neurons arrived on the planet. Their first mission was to make it possible to list and publish ads on the website.
Mission 1: base camp
Unit 1 quickly went through all his data concerning the building of websites. Almost all of them had a database so he decided that it was a safe bet to start with writing the database code. He also found a study of the millions of different programming languages available, which revealed that Go was the best language of all time. Using all this information, Unit 1 quickly produced the necessary code, very pleased with himself:
Even though he was confident about his code, Unit 1 knew that it was good practice to write tests, so he quickly proceeded to do that too:
Meanwhile, Tender Teddy talked to the future users of his website and started writing tests corresponding to the behavior the users wanted to see. Tender Teddy chose to use Go too, as it is a simple language that allows the coder to focus their mind on the users’ problems.
Tender Teddy was not the best coder in the room, but he was able to execute the implementation quickly and easily:
There was no persistence yet, but Tender Teddy was soon able to put his website in the hands of his users thanks to the 51st-century interface auto-generation technology, an impressive tool produced by the Not Any Code movement of the time.
Mission 2: search party
Just then, a giga-neuron emerged from hyperspace in a flash of photonic energy. A new instruction was being issued by the neocortical part of Gigamind at the center of the galaxy: Users would need to be able to search through trillions of classified ads with a full text search feature.
On hearing this, Unit 1 began to get frustrated. He hadn’t been able to show his first mission’s results yet as he had been focused on the database layer and still needed to implement the application layer. He was wondering how Tender Teddy had been able to show his results so soon. Was he cheating in some way? Maybe he was getting help from other members of his species?
Unit 1 quickly parsed the millions of data banks he had on full text search and realized 98% of websites were using a technology called Elasticsearch. This meant he needed to throw out all the database code he had produced so far and start from scratch with Elastic.
Unit 1 was falling behind schedule and didn’t have many users yet, so he decided to skip testing just this once, even though this had been considered good practice for more than 3,000 years.
Meanwhile, Tender Teddy received the new instruction from Gigamind with relief. He had been starting to get worried that his users would have trouble finding the ads relevant to them among the list of all the ads as his site was starting to get more and more users. Tender Teddy quickly set up a test to explore what it would look like to be able to search for ads from the point of view of his users.
Then he quickly proceeded to the simplest implementation — Tender Teddy’s site did not have so many users that he had to think about scale yet.
He then had to define what it would mean to have a matching ad:
All the other tests and code were still working as expected, so Tender Teddy did not have to touch those. The users who were not interested in the new feature were not impacted.
Mission 3: hyperspace
Another photonic burst, another giga-neuron arrived in the solar system. Gigamind was worried about competition and wanted to be able to reach customers more quickly throughout all the galaxies. For this, it was going to be necessary to implement the Hyperspace Textual Transfer Protocol (HTTP), otherwise there would be too much latency for the winning website to be usable.
At this point Unit 1 knew that he could not win the competition. So he went to spy on Tender Teddy to try to find out how the hell this little ball of fur had managed to beat him at coding. He saw Tender Teddy refactor his code with ease so that the tests he had set up before would still work with this new HTTP protocol.
He watched as Tender Teddy went on to define an interface for his software. Thanks to this interface he was able to expose the domain language to all the technical parts of the code.
Then he used the interface in the tests:
Finally he implemented the client:
Thanks to the interface, Tender Teddy was able to quickly implement the server code separate from the HTTP code, the domain code, and the database code (Unit 1 remembered that people used to call this hexagonal architecture; he wondered if their ancestors had been obsessed with geometry or something).
Also thanks to the interface, the tests could be used for the server now too:
And just like that, Tender Teddy had hyperspace functionality despite barely touching his tests — and he was guaranteed to be able to maintain functionality through the new protocol!
Amazed by what he saw, Unit 1 conceded the competition and asked Tender Teddy to be part of his engineering team. He figured that maybe he could learn something from Tender Teddy if he became part of his team and realized why all his own knowledge about technology and statistics had not been enough to help him win the competition.
Over the following decades Tender Teddy was able to deploy his website across the whole galaxy, making contact with all sorts of sentient beings. By talking to them, learning their needs and practices, he was able to adjust the behavior of his website so that it worked for everyone and he experienced amazing success. Unit 1 learnt from his good friend Tender Teddy that it’s better to focus more on the users and the behavior of the code they need from the beginning.
Epilogue
It was the beginning of the year 6024. Annie joined her computer archeology group for a little digging party. The team was searching through an old library of content on computers from the 51st century. They had put together a new DIY reading device for these antique storage devices and had already been through petabytes of not-so-interesting documentation and books describing the programming languages of the time when a picture caught Annie’s eye. It was the cover of a book picturing a sentient bear. The book was titled A Primer on Testing. Unfortunately, the author’s name was partially missing and she was only able to see some of the letters: “Tender T*DD*.” Her eyes widened as she quickly skimmed through the book. She called her friends from the digging party with excitement — “Hey, folks! I think I just found the inventor of TDD!”
My intention with this piece was to talk about test-driven development (TDD) in a simple and accessible way. Instead of diving into complicated terminology or engaging in endless debates about the methodology, I chose to tell a story that illustrates the core principles of TDD in a relatable and fun manner. By using the characters of Unit 1 and Tender Teddy, I hoped to make these concepts easier to grasp for readers who might not have a deep technical background, while still sparking a smile for those who do. I hope this story serves as a lighthearted introduction to TDD and encourages a practical, user-focused approach to coding.
You can access the complete code referenced in the article in a dedicated GitHub repository.
I would like to thank Anne-Laure Civeyrac for her kind pieces of advice without which I would not have written this article.
I would also like to thank my colleagues Laurent Dutheil, Borey Uk and Karen Pedie Koyou for taking the time to review this article.
