Jest Errors
7 common Jest errors with verified solutions.
Cannot find module './Component'
Jest could not resolve a module import. The file may not exist, the path may be wrong, or the module resolution config may be misconfigured.
SyntaxError: Unexpected token
Jest encountered syntax it cannot parse. This usually means a file needs to be transformed (e.g., TypeScript, JSX, ESM) but the transformer is not configured.
Snapshot mismatch — expected value to match snapshot
The rendered output does not match the stored snapshot. The component output changed since the snapshot was last updated.
Timeout — Async callback was not invoked within 5000ms
An async test did not complete within the default 5-second timeout. The async operation may be hanging, or done() was never called.
UnhandledPromiseRejectionWarning
A Promise was rejected but no .catch() handler or try/catch block caught the error. This can cause flaky tests or missed failures.
Jest mock not being called / not returning expected value
A jest.mock() or jest.fn() is not behaving as expected — either not being called, not returning the mocked value, or not intercepting the real implementation.
Jest: Failed to transform file
Jest's transformer (Babel, ts-jest, SWC) failed to process a file. The transformer may be misconfigured or the file contains unsupported syntax.