jestjs/jest · error · Error

Error: `.each` called with an empty Tagged Template Literal…

Error message

Error: `.each` called with an empty Tagged Template Literal of table data.

What it means

Thrown when `.each` is called with a tagged template literal whose first string segment (`table[0]`) is empty after trimming. This means the template literal contains no heading text at all, so there is no structure to parse column names from.

Solutions

Provide heading text in the template: `` test.each`a | b\n ${1} | ${2}` ``.
If you do not need headings, use array syntax instead: `test.each([[1, 2]])`.

Example fix

// before
test.each``('test', () => {});

// after
test.each`a | b
  ${1} | ${2}`('test $a', ({a, b}) => {});

Defensive patterns

Strategy: validation

Validate before calling

// For tagged template .each, validate the first segment is non-empty
function validateTemplateNotEmpty(templateStrings) {
  if (templateStrings[0] && templateStrings[0].trim() === '') {
    throw new Error('Template literal for .each must contain heading text');
  }
}

Type guard

function isNonEmptyTemplateString(arr: unknown): arr is TemplateStringsArray {
  return Array.isArray(arr) && typeof (arr as any[])[0] === 'string' && (arr as any[])[0].trim() !== '';
}

Prevention

Always include a heading row when using tagged template .each syntax.
Prefer array syntax for simple single-column test data.
Use a linter rule or code snippet template for .each to avoid empty templates.

When it happens

Trigger: Writing `` test.each`` `` (empty backticks with no content and no interpolations). The tagged template literal produces `['']` with `.raw = ['']`, and `isEmptyString('')` returns true.

Common situations: Accidentally leaving the template literal empty while scaffolding. A code-generation tool emitting an incomplete `.each` block. Copy-paste error leaving the template body blank.

Related errors

AI-assisted analysis of jestjs/jest@8e6d128e4a (2026-08-10). Data as JSON: /api/errors/06007e15a7b5207b. Report an issue: GitHub.

Appendix: source

Thrown at packages/jest-each/src/validation.ts:31

type TemplateData = Global.TemplateData;

const EXPECTED_COLOR = chalk.green;
const RECEIVED_COLOR = chalk.red;

export const validateArrayTable = (table: unknown): void => {
  if (!Array.isArray(table)) {
    throw new TypeError(
      '`.each` must be called with an Array or Tagged Template Literal.\n\n' +
        `Instead was called with: ${pretty(table, {
          maxDepth: 1,
          min: true,
        })}\n`,
    );
  }

  if (isTaggedTemplateLiteral(table)) {
    if (isEmptyString(table[0])) {
      throw new Error(
        'Error: `.each` called with an empty Tagged Template Literal of table data.\n',
      );
    }

    throw new Error(
      'Error: `.each` called with a Tagged Template Literal with no data, remember to interpolate with ${expression} syntax.\n',
    );
  }

  if (isEmptyTable(table)) {
    throw new Error(
      'Error: `.each` called with an empty Array of table data.\n',
    );
  }
};

const isTaggedTemplateLiteral = (array: any) => array.raw !== undefined;
const isEmptyTable = (table: Array<unknown>) => table.length === 0;

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