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Left of the Loop: The PO is Dead, Long Live the PO
When I wrote about shifting the engineering process left — spec sessions, autonomous agents, humans reviewing output rather than writing code — a question kept coming up. Where does the Product Owner fit in all of this? It’s the right question. And I think the answer is more interesting than “the PO disappears.” Let’s start with acceptance criteria. We invented them to bridge a gap. The team needed to know when something was done. The PO needed confidence that what got built matched the intent. Acceptance criteria were the contract between the two. But if the Spec Session is where intent gets defined — by the whole team, together, before the agent runs — that gap closes. What the team agreed on in the room is the definition of done. The spec is the acceptance criteria. You don’t need a separate validation step because the planning and the agreement happened at the same time. The tighter the loop, the less ceremony you need around it. There’s a caveat though. The spec is a necessary contract. It’s not a sufficient one. Simon Martinelli’s work on the AI Unified Process validates the spec-driven approach technically. But his model is about the artifact — requirements at the center, AI generating everything else from them. How the team actually builds shared understanding before the spec exists isn’t something it addresses. That’s not a criticism. It’s just a different question. A spec written after a real Spec Session — where the team worked through edge cases together, disagreed, got to resolution — is different from a spec written by one person and signed off asynchronously. Same artifact. Different quality of shared understanding. That distinction matters when the agent hits an edge case the spec didn’t anticipate. So what’s actually left for a dedicated PO? Two things. And they’re very different. The first is product thinking — challenging intent, representing user needs, asking why before the agent runs with something. That’s valuable. But it doesn’t require a ded
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Building ClaimMate AI
Hi everyone, I'm Marc, the founder of ClaimMate AI. I've been building an AI software engineering platform that helps developers generate code, explain existing code, debug issues, create tests, review code, and build applications from simple prompts or voice. I'm still in the early stages and would really appreciate honest feedback from other developers. Why I Built It I wanted one workspace where developers could chat with AI, generate code, debug problems, and iterate on ideas without constantly switching between multiple tools. I'd Love Your Feedback If you have a few minutes, I'd appreciate any thoughts on: Is the interface easy to understand? Which feature would you use most? What would stop you from using it regularly? What feature is missing? You can try it here: https://ClaimMateAI.pro I'm not looking for praise—I genuinely want constructive feedback that will help improve the product. Thanks for your time!
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𝗔𝗜 𝗘𝗻𝗴𝗶𝗻𝗲𝗲𝗿𝗶𝗻𝗴 𝗖𝗵𝗮𝗽𝘁𝗲𝗿 𝟯: 𝗪𝗵𝘆 𝗘𝘃𝗮𝗹𝘂𝗮𝘁𝗶𝗻𝗴 𝗔𝗜 𝗜𝘀 𝗛𝗮𝗿𝗱𝗲𝗿 𝗧𝗵𝗮𝗻 𝗜𝘁 𝗟𝗼𝗼𝗸𝘀
One of the biggest takeaways from Chapter 3 of AI Engineering was realizing that building an AI model is only part of the challenge. Figuring out 𝗵𝗼𝘄 𝘁𝗼 𝗲𝘃𝗮𝗹𝘂𝗮𝘁𝗲 𝗶𝘁 𝗳𝗮𝗶𝗿𝗹𝘆 𝗮𝗻𝗱 𝗮𝗰𝗰𝘂𝗿𝗮𝘁𝗲𝗹𝘆 can be just as difficult. With traditional software, it's usually easy to tell whether something works. If a calculation is wrong or a test fails, you know there's a bug. But AI doesn't always work that way. A model can generate multiple reasonable answers to the same question, making it much harder to determine which one is actually better. That made me think: 𝗛𝗼𝘄 𝗱𝗼 𝘄𝗲 𝗸𝗻𝗼𝘄 𝗶𝗳 𝗮𝗻 𝗔𝗜 𝗺𝗼𝗱𝗲𝗹 𝗶𝘀 𝗮𝗰𝘁𝘂𝗮𝗹𝗹𝘆 𝗶𝗺𝗽𝗿𝗼𝘃𝗶𝗻𝗴? 𝗕𝗲𝗻𝗰𝗵𝗺𝗮𝗿𝗸𝘀 𝗡𝗲𝗲𝗱 𝘁𝗼 𝗞𝗲𝗲𝗽 𝗘𝘃𝗼𝗹𝘃𝗶𝗻𝗴 Reading this section made me realize how difficult it is for evaluation benchmarks to keep up with the pace of AI development. The chapter explains that GLUE (General Language Understanding Evaluation) was introduced in 2018 to measure how well language models performed on common natural language tasks. But within about a year, models had already become so good at it that researchers introduced SuperGLUE in 2019 as a more difficult benchmark. GLUE evaluates tasks such as: Question answering Sentiment analysis Sentence similarity Text classification The chapter also mentions newer benchmarks like: SuperGLUE MMLU (Massive Multitask Language Understanding) MMLU-Pro Each one was introduced because the previous benchmark was no longer challenging enough. What I found interesting is that a model getting a higher benchmark score doesn't always mean it understands language better. Sometimes it simply means the model has become very good at solving that particular benchmark. 𝗨𝗻𝗱𝗲𝗿𝘀𝘁𝗮𝗻𝗱𝗶𝗻𝗴 𝗘𝗻𝘁𝗿𝗼𝗽𝘆 𝗮𝗻𝗱 𝗣𝗲𝗿𝗽𝗹𝗲𝘅𝗶𝘁𝘆 Another section I really enjoyed was the explanation of entropy and perplexity. The chapter explains entropy as a measure of how much information a token carries and how difficult it is to predict the next token in a sequence. Perplexity measures uncertainty. If a model is very uncertain about what comes next, its perplexity will be higher. If
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US investors will soon get access to SK Hynix, another memory maker riding the AI boom
SK Hynix is experiencing a boom credited to AI. It will ride that to a multibillion-dollar U.S. IPO, expected to take place on Friday.
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The 555 Timer: The Most Popular Chip Ever Made
Ask a room full of engineers to name the most popular integrated circuit ever made and you will hear guesses about famous microprocessors or memory chips. The real answer is far humbler: an eight-pin timer chip designed in 1971 that is still manufactured by the billion every single year. It is the 555 timer , and more than half a century after its debut it remains one of the first chips a student wires up and one of the last a veteran gives up on. A chip designed by one engineer The 555 was designed by Swiss-born engineer Hans Camenzind , working under contract to Signetics , and it reached the market in 1972. What made it remarkable was not raw speed or complexity but flexibility. Inside its tiny package sit a couple of dozen transistors, a handful of resistors, and two voltage comparators arranged around a simple voltage divider. Feed it a supply voltage, add one or two external resistors and a capacitor, and it will generate precise time delays and oscillations without any software at all. That analog-first design philosophy is exactly why it endured. By some estimates the 555 has been produced at a rate of around a billion units a year for decades, which comfortably earns it the title of probably the most popular IC ever made. It has flown on spacecraft, blinked in toys, and sat quietly on countless hobbyist breadboards. What the 555 actually does The 555 has three classic operating modes, and understanding them covers most of what you will ever need: Monostable — one stable state. A trigger produces a single output pulse of a fixed length set by an external resistor and capacitor. Think of a debounced button press or a timed relay. Astable — no stable state. The output oscillates continuously between high and low, producing a square wave. This is your blinking LED, your simple tone generator, or a rough clock source. Bistable — a basic flip-flop that latches between two states, useful as a simple set/reset memory element. None of this requires firmware, a cryst
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How Beginner Developers Can Find Great Project Ideas
Every beginner developer hits the same issue at some point. You learn a few basics, finish a tutorial, and then you have no idea what to build next. That gap can feel bigger than learning the code itself, because now the question is not “How do I write this?” but “What should I build at all?” This article is for that moment. I want to make it simple, practical, and useful, because project ideas do not need to be too advanced to be valuable. A good project is one that teaches you something, keeps you going, and gives you enough confidence to build the next one. Why project ideas are important There’s a common thing that I have noticed in most of the beginners, that is, watching too many tutorials. Tutorials are helpful, but actual learning starts when you try to build something on your own. That is when you start facing real decisions, small bugs, unclear logic, and the feeling of connecting different parts into one working product. That is one of the reasons why project ideas matter so much. The right idea gives you direction, but it also gives you energy. When the project feels too huge, you get stuck. When it feels too small or boring, you stop caring. The sweet spot is a project that feels possible and still a little exciting. This matters even more today. Tools like ChatGPT or Copilot can help you write code faster, but that doesn't solve the real problem beginners have. Writing the code was never the hard part for long but knowing what to build is. Start with problems you already know The easiest project ideas often come from your own life. Think about small things you do every day that feel annoying, repetitive, or messy. A simple to-do list, habit tracker, note saver, expense log, study planner, or meal planner can all become strong beginner projects if you build them well. This works because the problem is already familiar to you. You do not have to invent a fake use case or force a complicated feature list. You already know what the app should do, what feel
开源项目
Canadian spy agency says it hacked drug traffickers, extremists and a ransomware gang last year
The hacking operations disclosed in a Canadian spy agency's annual report underscores some pressing national security threats facing the country and its top allies.
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What Word Break Leetcode Problem Taught Me About Debugging Order
I recently worked through the classic Word Break problem in an interview. My approach was solid from the start — recursion with memoization, a breakable helper that tests every prefix and recurses on the rest. The logic was right. What slowed me down was everything around the logic. Here's the solution I landed on: class Solution { public: bool wordBreak ( string s , vector < string >& wordDict ) { unordered_set < string > dict ( wordDict . begin (), wordDict . end ()); unordered_map < size_t , bool > memo ; return breakable ( s , dict , memo , 0 ); // missed: breakable was a free function defined below -> "not declared in this scope" } private : // missed: had int here, compared against s.length() (size_t) -> sign-compare warnings bool breakable ( const string & s , const unordered_set < string >& dict , unordered_map < size_t , bool >& memo , size_t starting ) { if ( starting == s . length ()) return true ; if ( memo . count ( starting )) return memo [ starting ]; for ( size_t e = starting + 1 ; e <= s . length (); e ++ ) { string word = s . substr ( starting , e - starting ); // missed: shadowed an outer `word`, and had substr(starting, e) instead of e - starting if ( dict . count ( word ) && breakable ( s , dict , memo , e )) { memo [ starting ] = true ; // missed: wrote == instead of =, so success was never cached return true ; } } memo [ starting ] = false ; // missed: this line, so failures were never cached and memoization broke down return false ; } }; The real lesson Most of what tripped me up was syntax and scope — a function declared in the wrong place, signed/unsigned mismatches, a shadowed variable, == where I meant = . None of these were about the algorithm. But because I spent my time chasing them, I had less room to focus on the one thing that actually matters in this problem: the logical correctness of the memoization. The takeaway I'm keeping: get the syntax and scoping clean early, so the debugging budget goes toward logic, not typos. That's the
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Fundamental Concepts of Business Applications III: Locator Definitions
In the previous article, we argued that a Locator is neither a UI control nor a search mechanism. It is an architectural concept that resolves business references within a specific business context and transforms them into canonical business identities. If that is true, however, an obvious question immediately follows. How can a Locator be described? Not how it is implemented. Not how it is executed. But how it can be described independently of any particular implementation. This question is more important than it may seem at first glance. If two different development teams decide to implement a Locator, how can they be sure they are implementing the same concept? How can we discuss a Locator without referring to a particular library, programming language, or framework? The answer is that, like any mature architectural concept, a Locator must first be separated from its implementation. This distinction appears repeatedly throughout the history of software engineering. Relational theory existed before relational database systems. SQL does not describe how a query will be executed. It describes only the result we want to obtain. The choice of indexes, execution plans, and optimization algorithms is the responsibility of the query optimizer. Exactly the same principle applies here. A Locator should not be defined by the mechanism that implements it. It should be possible to describe it independently of that mechanism. This naturally leads to three distinct levels of abstraction. Locator Pattern │ ▼ Locator Definition │ ▼ Execution Engine The Locator Pattern is the architectural concept itself. The Locator Definition is the declarative description of a particular resolution process. The Execution Engine is the component responsible for interpreting that description and performing the actual resolution. Each level has a different responsibility, and they should never be confused with one another. This means that a Locator Definition is not an implementation artifact. It
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Smart glasses maker Even Realities hits $1B valuation with $150M funding led by Meituan, Tencent
Even Realities, an ex-Apple team building camera-free smart glasses, raised $150M from Meituan and Tencent at a $1B valuation.
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What AGENTS.md Gives Coding Agents That README Files Do Not
Here's the failure mode I keep running into. A team gives a coding agent a repo, a task, and maybe a README. The agent can find files and write code, but it still has to guess the operating rules. It guesses the package manager. It guesses which checks matter. It guesses whether generated files are safe to edit. It guesses what "done" means. A README is usually for humans: what the project is, how to run it, and where the important docs live. A coding agent needs different context. Setup rules. Test commands. Boundaries. Completion criteria. That's the gap AGENTS.md fills. The official AGENTS.md guidance describes it as a predictable place for coding-agent instructions: setup commands, test commands, code style, security considerations, and nested instructions for large monorepos. I find the split useful in a more boring way. The README answers, "What is this project?" AGENTS.md answers, "What should an agent know before touching it?" That second question is where the work usually gets fragile. Where Goose Fits Goose makes this less theoretical because it isn't just a chat box. It's an open source local AI agent with a desktop app, CLI, API, MCP extensions, and skills. Without AGENTS.md , I find myself writing prompts like this: Update the docs, but don't touch generated files, use pnpm, run the lint and test commands, keep the PR small, and tell me what you couldn't verify. With AGENTS.md , the prompt can get shorter: Update the quickstart docs for the new config flag. Goose can run the task in the repo. The repo can carry the standing instructions. I noticed this on a small docs/config update where generated files sat near source files. Without repo instructions, the prompt had to carry the package manager, generated-file boundary, checks, and the "tell me what you could not verify" rule. Once those rules lived in AGENTS.md , the prompt became just the task. Not magic. Just fewer chances to forget the boring parts. Where Skills Fit I would add one more layer once
开发者
How a Hollywood Star Helped Invent Wi-Fi
One of the most important ideas in modern wireless communication did not come out of a corporate research lab or a defense contractor. It was patented in 1942 by one of the most famous movie stars of the era, working alongside an avant-garde composer. The actress was Hedy Lamarr, and the technique she helped invent, frequency hopping , is a direct ancestor of the Wi-Fi, Bluetooth, and GPS signals your devices rely on every day. The patent Hollywood forgot At the height of her Hollywood fame, Hedy Lamarr was also a self-taught inventor who tinkered between film shoots. Early in World War II she became fixed on a hard problem: radio-controlled torpedoes were easy to jam, because an enemy who found the single control frequency could simply drown it in noise and send the weapon off course. Working with composer George Antheil, she designed a system where the transmitter and receiver would rapidly and secretly switch together across many different frequencies. Antheil, who had once synchronized sixteen player pianos for a concert piece, suggested using a slotted paper roll like a player piano to keep both ends hopping in step across 88 frequencies , the same number as the keys on a piano. On August 11, 1942, they received U.S. Patent 2,292,387 for a "Secret Communication System." The U.S. Navy filed the idea away and did not use it during the war. For decades the patent sat largely forgotten, and Lamarr received no money and little recognition for it in her lifetime. She was finally inducted into the National Inventors Hall of Fame in 2014, years after her death. What frequency hopping actually does The core insight is deceptively simple. Instead of putting a signal on one fixed frequency, you spread it across many frequencies in a pattern that only the sender and receiver know. Both ends "hop" in perfect synchronization, dwelling on each frequency for only a fraction of a second before jumping to the next. This buys you two enormous advantages. It is very hard to jam, b
创业投融资
5 desk gadgets that can make your workday better
The right desk gadgets can help you reduce clutter, stay focused, and add a little extra convenience to your day.
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AI's Impact on Junior Developer Roles: A New Era
The Evolution of Junior Developer Roles in the Age of AI In the tech industry, a pressing question has emerged: Is the role of junior developers disappearing? With the rapid advancement of artificial intelligence (AI), particularly generative models like ChatGPT, there's growing concern about the future of entry-level software development jobs. While some predict a decline, the reality is more nuanced. AI is transforming these roles, not eliminating them, creating new opportunities for junior developers who adapt to the changing landscape. TL;DR AI advancements are reshaping junior developer roles rather than removing them. AI tools reduce the need for routine coding tasks but create opportunities for those focusing on higher-order skills like problem-solving and collaboration. Junior developers should embrace AI tools to enhance creative problem-solving. Companies must adapt talent strategies to nurture junior developers for future senior roles. The Transformation of Junior Developer Roles AI's Impact on Routine Coding Tasks Artificial intelligence has significantly automated routine coding tasks. AI models, such as ChatGPT, can generate code snippets, debug errors, and optimize performance. This capability shifts junior developers' focus from these tasks, traditionally a large part of their responsibilities. Code Generation : AI can produce boilerplate code, reducing the time spent on repetitive tasks. Error Detection : AI-driven tools identify and propose fixes for common coding errors, streamlining debugging. Performance Optimization : AI algorithms can automatically enhance code efficiency, which previously required manual intervention. Changing Nature of Junior Developer Roles The employment rate for junior developers aged 22-25 has declined nearly 20% from its peak in 2022. This trend indicates a shift in how entry-level positions are perceived and utilized within tech companies. With AI handling routine tasks, the role of a junior developer is evolving to em
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Building CogneeCode - AI Developer Memory Assistant
🧠 Building CogneeCode - AI Developer Memory Assistant The Problem Every developer faces the problem of lost context. "Why did I make this decision 3 months ago?" "How did I fix this bug last week?" Current AI tools forget everything between sessions. This is a real problem that wastes hours of developer time. My Solution CogneeCode is an AI developer memory assistant that builds a permanent knowledge graph using Cognee Cloud . It remembers every decision, bug fix, and code context you give it. What It Does ✅ Log architectural decisions with tags and context ✅ Log bug fixes with error messages and solutions ✅ Ask natural language questions about your codebase ✅ Get answers with evidence citations from the knowledge graph ✅ Semantic search across all memories ✅ Visual timeline of all decisions and bug fixes ✅ Analytics dashboard showing memory insights ✅ Knowledge graph visualization Tech Stack Backend: Flask (Python) Memory Layer: Cognee Cloud LLM: Groq Llama 3.3 Frontend: Vanilla HTML + CSS + JS Icons: Tabler Icons Cognee Cloud APIs Used remember() - Save decisions and bug fixes with metadata recall() - Natural language queries with evidence citations search() - Semantic search across memories visualize() - Knowledge graph visualization improve() - Memory graph enrichment forget() - Remove outdated memories Why This Matters When you return to a project after months, all your reasoning and solutions are still there, searchable in natural language. No more "Why did I do this?" or "How did I fix this bug?" Demo Watch the video: https://youtu.be/TNcBIBuPW7c Links 🔗 GitHub: https://github.com/JOSESAMUEL14/cogneecode 🔗 Live Demo: https://josesamuel.pythonanywhere.com AI Assistance Disclosure Built with assistance from Claude and Gemini AI. Built for WeMakeDevs x Cognee Hackathon 2026 Category: Best Use of Cognee Cloud ⭐ Star the repo if you find it useful!
开发者
My Journey to Becoming a Full-Stack Developer and Software Engineer
Hello, DEV Community! 👋 Hi everyone! My name is Sulemana Abdallah , and I'm excited to be part of the DEV Community. I'm passionate about software development and enjoy building modern, responsive web applications using: HTML CSS JavaScript TypeScript React Python My goal is to become a skilled Full-Stack Developer and Software Engineer while continuously learning and building real-world projects. I joined DEV to: Learn from experienced developers. Share my projects and progress. Write about what I learn. Connect with developers from around the world. I'm looking forward to growing with this amazing community. Thanks for reading! 🚀
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📦 AI Context Engineering (Part 2): Tokens, Context Windows & Memory - Why More Context Isn't Always Better
In Part 1 , we learned that building great AI applications isn't just about writing better prompts. It's about providing the right context . But that naturally leads to another question: How much context can an AI actually understand? If you've used ChatGPT, Claude, Gemini, Cursor or any AI coding assistant for a while, you've probably experienced something like this. 🤔 "Didn't I Already Tell You That?" Imagine you're debugging a production issue with an AI assistant. You start by explaining the architecture. Then you share the API flow. Then database schema. Then logs. Then stack traces. After 30 minutes of conversation, you ask: "So what's causing the bug?" Instead of giving the answer, the AI responds: "Could you share your database schema?" You stare at the screen. "I already did..." Sometimes it even forgets details from earlier in the same conversation. Naturally, people assume: The AI has bad memory. The model is unreliable. The conversation is broken. In reality, something completely different is happening. You're running into one of the most important concepts in modern AI systems: The Context Window. Understanding this concept changes how you interact with AI—and more importantly, how you build AI-powered applications. 🧠 Before We Talk About Context Windows… We first need to understand something much smaller. Tokens. Almost every AI provider mentions them. Pricing is based on them. Context windows are measured using them. Yet many developers still think: 1 token = 1 word That isn't true. 🔤 What Exactly Is a Token? A token is the basic unit of text that an AI model processes. Humans naturally read text as: Characters Words Sentences Large Language Models don't. Before text reaches the model, it's converted into smaller pieces called tokens by a tokenizer. The model never sees your original sentence. It only sees a sequence of tokens. Think of a tokenizer as a translator between humans and AI. You write English ↓ Tokenizer ↓ Sequence of Tokens ↓ LLM The toke
产品设计
Why IoT Modules Still Use 1981 AT Commands
If you have ever wired up a cellular modem, a WiFi module, or a Bluetooth radio and typed something like AT+CGMR into a serial terminal, you have used a command language that is older than most of the engineers using it. The humble AT command set that still configures a huge share of today's connected hardware was born in 1981 , with a device called the Hayes Smartmodem. Four decades and billions of devices later, it refuses to die, and that longevity has a lesson in it for anyone building embedded systems. What AT actually stands for When Dennis Hayes and his company released the Hayes Smartmodem 300 in 1981, they faced a small but real design problem: how does a computer tell a modem the difference between a command to the modem and data to be sent down the phone line ? Their answer was an attention sequence. Every command line began with the two letters AT , short for attention , which told the modem to wake up and listen to what followed. ATD dialled a number, ATH hung up, and so on. It was readable, it was easy to implement on the microcontrollers of the day, and crucially you could type it by hand to debug a link. That simplicity is exactly why it spread. Competing modem makers cloned the Hayes command set to stay compatible, it became a de facto industry standard, and later it was formally captured in telecom standards. A convention that started as one company's pragmatic shortcut turned into the lingua franca of getting a device onto a network. From phone lines to the Internet of Things Here is the part that surprises people. The AT command set never retired when dial-up modems did. It quietly migrated into the components that make modern IoT possible. Cellular modules that put a device on a 4G or LTE network, from vendors like Quectel, SIMCom, and u-blox, are almost universally driven by AT commands. Classic Bluetooth and many WiFi modules expose an AT interface too. Even the ESP8266 and ESP32, the microcontrollers behind an enormous number of hobby and com
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Hey Everyone!
This is my first post here, so I'm going to use it as an introduction. I'm Usman, a software + data engineer who primarily works with data pipelines, backend systems. Not a huge fan of frontend development though. Although I do what I can, projects honestly feel incomplete without them, because at the end of the day you do have to showcase a working end to end system when you build something. I'm here after dozens of incomplete personal projects, and projects that never even got past the design phase, you know the drill. Procrastination and imposter syndrome kept stopping me from taking the next step, but I'm here now, gotta keep myself in check fr. I was scrolling through LinkedIn the past few days, and oh my god, the amount of AI-related brain rot there. Every single post written by AI, telling you how to use AI and how not to use AI. I mean I get it, yeah, the paradigm is shifting and AI is essential to development, but where are your personal anecdotes, stuff you solved, stuff you learned, the challenges you faced, how you overcame them. You know what maybe it's my fault, it's my algorithm after all. Anyway, here I am, looking to interact with like-minded engineers and learn from them. I'm also going to post regularly about my progress and what I am building, even though I have quite a bit of experience, and have built and contributed to large-scale production systems and pipelines, I'm going to start with something small, so I can stay consistent and keep myself in check. Software engineering fascinates me a lot, and there are so many domains that I wish to explore and have explored like game development, data engineering, web/app development. My significant other is graduating in a few days, and I'm thinking of making a small game for her, alongside which I'll be working on a small sales lead enrichment pipeline. Hoping to showcase my work and document it publicly, and hoping to get to know and learn from you all! Also, I'd love to know your thoughts on the am
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Testing Best Practices in Python
Introduction Python's testing tools are lightweight enough that it's easy to write a lot of tests without writing good ones. A suite that mocks every collaborator, duplicates the same assertion ten times with different inputs pasted in by hand, or chases a coverage number will pass in CI and still miss real bugs. pytest gives you fixtures, parametrize , and monkeypatch — the tools that make it just as easy to write the right tests as the wrong ones. This post covers how to use them well. Test at the Right Level: the Pyramid Not every test should look the same. The test pyramid is a rough guide to where your effort should go: Unit tests — the bulk of the suite. Pure functions and classes, no I/O, no real database. Milliseconds each. Integration tests — fewer of these. Verify the seams : does your ORM query actually produce correct SQL against a real database, does your HTTP client actually parse a real response. End-to-end tests — a handful. Cover the critical flows through the whole stack, accepting they're slower and more brittle. # Unit — pure logic, no database, no framework def test_applies_ten_percent_discount_for_orders_over_100 (): calculator = DiscountCalculator () total = calculator . apply ( order_total = 150.0 ) assert total == pytest . approx ( 135.0 ) # Integration — the seam that matters: our query against a real database import pytest @pytest.fixture def db_session ( postgres_container ): # real Postgres in a test container, not mocked with postgres_container . session () as session : yield session def test_finds_orders_placed_in_the_last_week ( db_session ): db_session . add ( Order ( id = " ord-1 " , placed_at = datetime . now ( UTC ))) db_session . commit () recent = order_repository . find_recent ( db_session , within = timedelta ( days = 7 )) assert len ( recent ) == 1 A unit suite that never touches a database runs in seconds and catches most logic bugs. A handful of integration tests catch what only shows up at the boundary — the query that's s