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Vitest · Matcher

toBeNumber

toBeNumber is an expectTypeOf matcher that checks whether a value has the static TypeScript type number. It is used in Vitest type tests, which the compiler analyzes instead of running.

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Syntax

expectTypeOf(value).toBeNumber()

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  • expectTypeOf
  • toBeString
  • toBeVoid
  • assertType
  • *.test-d.ts

Source: Testing Types | Guide | Vitest. Checked 2026-11-03.