Hello. I’m Jane , a QA engineer working with multiple QA engineers covering various products, mainly focused on Human Resources. This is the thirteenth day of freee QA Advent Calendar 2025. Thanks to a movie night with my little one, I found my topic.
Introduction
Think back to the great Chef Gusteau from the movie Ratatouille. His famous motto was: "Anyone can cook, but only the fearless can be great." As a QA Engineer, I believe this motto is also true for quality. Anyone can test software, but only the fearless—the ones who look for the hidden problems and fix broken processes—can achieve greatness. This journey from simple tester to great process optimizer is where Lean Six Sigma steps in. It gives us the structure to be fearless in hunting down chaos, whether we are building software or building dinner.
A great QA Engineer is not just a tester; they are an expert in process improvement. This work attitude, known formally as Lean Six Sigma, means we hunt for two things everywhere: Waste (from the "Lean" side) and Mistakes (from the "Six Sigma" side). The goal is always the same: get high-quality results predictably. What happens when we take these powerful rules out of the office? We find that the process of building software and the process of cooking a meal share the same problems—and both can be fixed with the same powerful tools.
First, let’s look at Lean. Lean principles focus on removing waste from a process. In software testing, waste often means time spent waiting for test environments, writing documents no one reads, or repeating the same manual tests every day. These non-value-added steps slow down the entire development team. To "go Lean," we reduce these wasted steps. We simplify our plans and focus only on the testing that gives the customer the most value.
Now, apply Lean's sharp focus to the kitchen. Cooking is often full of waste! Think about it: running to the store mid-recipe for a forgotten spice (wasted time), throwing away spoiled vegetables (wasted materials), or just standing around waiting for the oven to warm up (wasted waiting). A Lean cook aims to eliminate this kitchen chaos. This means organizing the pantry (reducing the time searching for ingredients), batch prepping vegetables (reducing repeated effort), and buying only what is needed (reducing spoiled food). It's all about making the process flow smoothly.
Next comes the heavy artillery: the Six Sigma side. This focuses intensely on reducing Mistakes (Defects) and Variation. A Six Sigma process aims for near-perfect quality, meaning the result is almost the same every time, making your software (or your food) perfectly reliable. In testing, this means using the DMAIC cycle (Define, Measure, Analyze, Improve, and Control) to investigate why certain bugs are still escaping to customers. We need to reduce the natural "variation" that happens when different engineers test different ways, leading to inconsistent quality and unpredictable release dates.
In the kitchen, Six Sigma means consistent quality. A mistake is a dish that tastes bad, burns easily, or doesn't look like the recipe photo. Variation is when a dish is perfect on Monday but awful on Friday. A Six Sigma cook stops guessing! They Measure their process by always using measuring cups and timers. They follow a standardized recipe (a document of clear steps) every single time. This dedication to exact measurement ensures that the ingredients—the "inputs"—always produce the desired, high-quality "output."
A powerful tool that links these two worlds is the 5 Whys. This simple method helps us dig past the obvious problem to find the real, hidden reason. In software, if a critical bug escaped to production, we don't just blame the tester. We ask: Why did the bug escape? (Because the test case was missing.) Why was it missing? (Because we didn't update the plan.) Why didn't we update the plan? (Because the document owner was too busy.) By the fifth "Why," we uncover a root cause, like a broken team process, not a broken person.
In the kitchen, the 5 Whys stops us from just getting mad at a burnt cake. Why is the cake burnt? (The top got too dark.) Why did the top get dark? (The oven was too hot.) Why was the oven too hot? (Because I guessed the temperature.) Why did I guess? (Because the oven dial is broken.) The final "Why" reveals the true process defect: a broken measuring tool! The solution is fixing the oven, not just watching the cake closer. This applies to both the server room and the kitchen: fixing the process tool is better than fixing the mistake over and over.
In the end, whether we are building software or cooking a masterpiece, Lean Six Sigma makes us better at finding hidden problems and creating predictable success. It teaches us that chaos is just an unoptimized process waiting for a QA mindset. Whether at work or in life decisions, once a QA, always a QA. With the addition of Lean Six Sigma, our output will always get better.
Now, go implement your control plan and deliver your next Lean-Six-Sigma-level outstanding project/dish!
The article シンプルに基礎が大事。入社3ヶ月のQAがチームでのAI活用を推進する上で分かったこと written by nino -san , QA engineer of Accounting QA team will be published tomorrow.
Let’s keep good quality~
