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Jest · Function

expect.extend

expect.extend adds custom matchers to Jest. A matcher returns pass and message values that control assertion results and failure output.

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Syntax

expect.extend(matchers)

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  • expect
  • expect.addEqualityTesters
  • expect.addSnapshotSerializer
  • expect.assertions
  • expect.hasAssertions
  • setupFilesAfterEnv

Source: Expect · Jest. Checked 2026-11-03.