Adopting Meticulous allowed Notion to gain full visibility into every UI impact, enabling engineers to increase performance and ship with confidence.
“We enabled Meticulous, and within weeks it found regressions we never would’ve caught with traditional testing.”
– Erdem Alparslan, Head of Developer Experience, Notion
5-10
bugs caught on average every week
5
engineering hours saved per engineer per week
30%
reduction in frontend testing and maintenance effort
THE PROBLEM
Notion’s co-founders and Erdem Alparslan, Head of Developer Experience were sitting in a room pressed with a challenge: how can we improve the reliability of Notion?
"We wanted to shift left and catch regressions earlier, but weren’t sure whether to hire more people, build new frameworks, or reorganize teams," said Erdem.
Notion is praised for its versatility as an all-in-one workspace, used by 100s of millions of people worldwide. What most users don’t see is the thousands of UI permutations, nested components, and customizable experiences that makes testing exceptionally challenging. A single component can render differently in 10-20 contexts based on subtle differences, making testing nearly impossible with traditional tools.
As the team continued to grow, they needed a way to catch regressions earlier and more reliably - without slowing development.
THE Solution
When the co-founders asked their community for modern testing tools capable of handling Notion’s complexity, Meticulous kept coming up. Eventually, they decided to give it a try.
“We enabled the tool, and within weeks, Meticulous found regressions we never imagined,” Erdem said. “People came to me and said, ‘If we don’t move forward with this, we’d be very unhappy.”
THE VALUE
Limiting Meticulous to a subset of teams didn’t make sense for a product as interconnected as Notion, where small changes can ripple across multiple components. After a successful pilot, the tool was rolled out across the entire engineering organization - and the impact was immediate.
Regressions were caught earlier, before releases, and engineers became more confident shipping new features, knowing that Meticulous would catch even the smallest edge-case bugs.
"We had a tricky bug where an inline database view inside a peek view inside a database page would trigger a visual issue in dark mode," said Ben Kraft. "Even with the best testing culture, nobody would have written a test for that case."
“Meticulous felt easy. It caught edge cases we never would have written tests for because it’s using real user flows, not just a simplistic script.”
Meticulous didn’t just catch bugs - it gave engineers time back.
Individual engineers estimate saving up to five hours per week, which compounds into massive productivity gains across Notion’s hundreds-strong engineering team.
Profile
Industry
Productivity Tech
Age of codebase
13 years
Engineers
400+
“If we had tried to build our own end-to-end testing framework, it would’ve taken multiple quarters. Meticulous delivered value almost immediately.”
For Notion’s first Design Engineer Tamara Chu, Meticulous fundamentally changed how fast she could work.
“It’s hard to quantify, but it feels like I’m working 2–5x faster,” she said. “I’ve worked on design systems and component libraries for a long time, and this is the first time I’ve used a tool where I’ve felt like, wow, this makes the speed I work at feel measurably faster.”
One of Tamara’s largest migrations involved replacing thousands of icons across Notion - it was only feasible because Meticulous validated changes across hundreds of real screens automatically.
Beyond the technical wins, Meticulous triggered a cultural shift.
Engineers began experimenting more freely without hesitation. Instead of asking “Can we delete this?” or “Does this break anything?”, they just made the change and checked to see if Meticulous caught anything. Meticulous provided a safety net that made iteration fast and safe.
As Notion embraced AI code generation, the bottleneck in software development had shifted to validation and code review.
Simon Last, Notion’s co-founder, now manages multiple AI coding agents in parallel and Meticulous plays a critical role in reviewing their changes before they reach production.
“It lets us adopt AI much more confidently,” said Erdem. “Engineers don’t have to wonder what they might break.”
Monthly Test Run Stats
312,930
user flows mapped
25,342
test runs
237,596,310
user sessions replayed
“Hiring engineers, writing tests, maintaining them? That’s all expensive. I felt very, very successful that I didn’t invest with my people or engineering time or projects. I just enabled a tool and it does the job.”
Long term Results
Today, Meticulous is deeply embedded in every engineer’s workflow and covers 70% of Notion’s most critical frontend functionality. Engineers receive rich visual diffs directly in pull requests, instantly seeing how changes affect real product flows.
Review cycles are faster, clearer, and more reliable - saving time for both authors and reviewers. From large design migrations to adopting AI codegen tools, Meticulous has helped Notion move faster - without compromising reliability for millions of users.
“I thought, ‘There’s so much they’d have to get right for this to work.’ But Meticulous does work. It’s impressive. And it’s become essential to how we build Notion.”
