Getting Strict: TypeScript's Big Test Suite Makeover
Daniel Rosenwasser is leading a major effort to enable strict mode by default in TypeScript, with two substantial PRs updating hundreds of test files to explicitly handle strict mode settings. The team is methodically preparing the codebase for this significant shift, touching over 275 files across project tests, evaluation tests, and fourslash tests.
Duration: PT3M46S
Episode overview
This episode is a short developer briefing from TypeScript.
It explains recent repository work in plain language.
- Show: TypeScript
- Published: 2026-01-21T11:10:12Z
- Audio duration: PT3M46S
Transcript excerpt
This excerpt keeps the crawler page concise. Listen to the episode or use the RSS feed for the full update.
Hey there, fellow developers! Welcome back to another episode of the TypeScript podcast. I'm your host, and wow, do we have an interesting story unfolding in the TypeScript codebase today - January 21st, 2026.
You know how sometimes you see those massive PRs that touch hundreds of files and you think "oh no, what went wrong?" Well, today's activity is the complete opposite - it's actually a really exciting glimpse into some serious forward-thinking work happening in the TypeScript team.
So the big story today is all about Daniel Rosenwasser, who's been absolutely crushing it with what I like to call "The Great Strictness Migration." We've got two major pull requests that are part of a larger effort to flip TypeScript's strict mode on by default. And let me tell you, the scale of this work is…
The first PR, number 63024, is a beast - it touched 260 files with over 340 additions and 83 deletions. What Daniel did here was systematically go through project tests, evaluation tests, and fourslash tests to explicitly set "strict: false" where needed. Now, you might be thinking "wait, why are they turning strict…
Think about it like this: if you're testing how TypeScript behaves in…
The…