bundleTestExports = exports => {
  const symbols = Object.getOwnPropertySymbols(exports).filter(
    name => name !== Symbol.toStringTag,
  );
  symbols.length > 0 &&
    Fail`exports must not have symbol-named properties, got: ${symbols.map(String).join(', ')}`;
  return {
    moduleFormat: 'test',
    [Symbol.for('exports')]: exports,
  };
}
A utility function for producing test bundles, which are not serializable
as JSON or passable.
@param {Record<PropertyKey, unknown>} exports