ts-jest "Cannot find name 'describe'" - Missing Jest Types

By Kaveh Alemi·Latchkey

TypeScript could not find the globals describe, it, and expect because the Jest type definitions are not loaded. Either @types/jest is missing, or tsconfig restricts types and excludes it.

What this error means

Compilation fails with "Cannot find name 'describe'." (and the same for it/expect/beforeEach). It typically appears after enabling types in tsconfig or when @types/jest was not installed in CI.

src/cart.test.ts:3:1 - error TS2304: Cannot find name 'describe'.

3 describe('cart', () => {
  ~~~~~~~~

Diagnose it: flake, environment, or genuine failure?

Before debugging the assertion, establish whether the test is deterministic. A test that fails only in CI is usually order-dependent, time-dependent, or racing something, and fixing the assertion will not help.

# does it fail in isolation?
npx vitest run path/to/file.test.ts

# is it order dependent? run the suite in a random order twice
npx vitest run --sequence.shuffle

# is it a race? run the same file repeatedly
for i in $(seq 1 20); do npx vitest run path/to/file.test.ts || break; done

Common causes

@types/jest not installed

The Jest global type definitions are not in node_modules, so TypeScript has no declaration for describe/it/expect.

tsconfig "types" excludes jest

Setting compilerOptions.types restricts which @types packages load. If jest is not in the list, its globals are not in scope even when installed.

How to fix it

Install the Jest type definitions

npm install -D @types/jest
# (or use Vitest globals / @jest/globals imports instead)

Include jest in tsconfig types

// tsconfig.json
{
  "compilerOptions": {
    "types": ["jest", "node"]
  }
}

CI-only causes worth ruling out

• Runners have fewer cores than a laptop, so timing-sensitive tests that pass locally fail under contention.
• No TTY and a different locale or timezone. Snapshot tests containing formatted dates or numbers are the usual casualty; pin TZ and LANG in the job.
• Parallel workers sharing a database, a port, or a temp directory. Give each worker its own namespace.
• Default timeouts calibrated on a fast machine. A cold runner is slower on first execution, especially before any cache warms.

How to prevent it

• Keep @types/jest in devDependencies and the lockfile.
• If you set types in tsconfig, include jest explicitly.
• Run tsc --noEmit in CI so type errors surface before tests.

Frequently asked questions

Related guides

References

• GitHub Actions documentation