jestjs/jest · error · Error

${matcherHint(...)} Inline snapshot must be a string ${print

Error message

${matcherHint(...)} Inline snapshot must be a string
${printWithType('Inline snapshot', inlineSnapshot, serialize)}

What it means

Thrown by `toMatchInlineSnapshot` (index.ts:251-259) in the 3-argument form when the third argument (the inline snapshot) is not a string. The 3-arg form is `toMatchInlineSnapshot(properties, inlineSnapshot)`, so the inline snapshot must be a string literal.

Source

Thrown at packages/jest-snapshot/src/index.ts:252

    if (
      typeof propertiesOrSnapshot !== 'object' ||
      propertiesOrSnapshot === null
    ) {
      throw new Error(
        matcherErrorMessage(
          matcherHint(matcherName, undefined, PROPERTIES_ARG, options),
          `Expected ${EXPECTED_COLOR('properties')} must be an object`,
          printWithType(
            'Expected properties',
            propertiesOrSnapshot,
            printExpected,
          ),
        ),
      );
    }

    if (length === 3 && typeof inlineSnapshot !== 'string') {
      throw new Error(
        matcherErrorMessage(
          matcherHint(matcherName, undefined, PROPERTIES_ARG, options),
          'Inline snapshot must be a string',
          printWithType('Inline snapshot', inlineSnapshot, serialize),
        ),
      );
    }

    properties = propertiesOrSnapshot;
  }

  return _toMatchSnapshot({
    context: this,
    inlineSnapshot:
      inlineSnapshot === undefined
        ? undefined
        : stripAddedIndentation(inlineSnapshot),
    isInline: true,

View on GitHub (pinned to f49721c78e)

Solutions

1. Pass the inline snapshot as a backtick string: toMatchInlineSnapshot(props, `"expected"`).
2. Let Jest write it: call `toMatchInlineSnapshot(props)` with no third arg and run with `-u`.

Example fix

// before
expect(x).toMatchInlineSnapshot({ code: 200 }, { body: 'ok' });

// after
expect(x).toMatchInlineSnapshot(
  { code: 200 },
  `
    Object {
      "body": "ok",
    }
  `
);

if (inlineSnapshot !== undefined && typeof inlineSnapshot !== 'string') {
  throw new Error('Third arg to toMatchInlineSnapshot must be a string');
}
expect(x).toMatchInlineSnapshot(props, inlineSnapshot);

function isOptionalString(v: unknown): v is string | undefined {
  return v === undefined || typeof v === 'string';
}

When it happens

Trigger: `expect(x).toMatchInlineSnapshot({ a: 1 }, 123)` or `toMatchInlineSnapshot(props, { not: 'a string' })`. The third arg is meant to be a backtick template literal.

Common situations: Passing a serialized object instead of a string. Copy-paste from a non-inline matcher that accepts different argument types.

Related errors

• ${matcherHint(...)} Expected properties must be an object ${
• ${matcherHint(...)} Expected properties must be an object ${
• ${matcherHintFromConfig(...)} received value must be an obje
• ${matcherHint(...)} received value must be a function ${prin
• Jest: Couldn't infer stack frame for inline snapshot.

AI-assisted analysis of jestjs/jest@f49721c78e (2026-08-03). Data as JSON: /data/errors/87c0f18c60ceb07d.json. Report an issue: GitHub.