Exercises
AI-written code with real defects. Find them, fix them, write the tests that catch them.
Pagination that loses the last item
Logic · TS · 5 min · A list endpoint in a REST API
●○○freeThe age validator that only tested the happy path
Tests · TS · 5 min · The signup form of a consumer web app
●○○freeThe avatar that crashes on an empty name
Edge cases · TS · 5 min · An avatar component in a team dashboard
●○○freeThe leaderboard where 9 beats 10
APIs and contracts · TS · 5 min · A leaderboard in a fitness app
●○○freeThe redirect check that trusts a leading slash
Security · TS · 5 min · The post-login redirect in an Express API
●○○freeShipping tests that only confirm the code
Tests · TS · 8 min · The checkout service of an online store
●●○The leaderboard that forgets who it skipped
Logic · TS · 8 min · A leaderboard in a quiz app
●●○The sanitizer that strips ../ exactly once
Security · TS · 8 min · The file upload handler of a document management service
●●○The slug that eats accented letters
Edge cases · TS · 7 min · Post URLs in a multilingual blog platform
●●○The view that rewrites the store
APIs and contracts · TS · 8 min · Sorted views in a to-do app's task store
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