function shouldWarn() {
  const answer = !haveWarned;
  /* istanbul ignore if */
  if (!isTest()) {
    haveWarned = true;
  }
  return answer;
}

  public match(
    idValue: IdValue,
    typeCondition: string,
    context: ReadStoreContext,
  ): boolean {
    const obj = context.store.get(idValue.id);

    if (!obj) {
      return false;
    }

    if (!obj.__typename) {
      if (!haveWarned) {
        console.warn(`You're using fragments in your queries, but either don't have the addTypename:
  true option set in Apollo Client, or you are trying to write a fragment to the store without the __typename.
   Please turn on the addTypename option and include __typename when writing fragments so that Apollo Client
   can accurately match fragments.`);
        console.warn(
          'Could not find __typename on Fragment ',
          typeCondition,
          obj,
        );
        console.warn(
          `DEPRECATION WARNING: using fragments without __typename is unsupported behavior ` +
            `and will be removed in future versions of Apollo client. You should fix this and set addTypename to true now.`,
        );

        /* istanbul ignore if */
        if (!isTest()) {
          // When running tests, we want to print the warning every time
          haveWarned = true;
        }
      }

      context.returnPartialData = true;
      return true;
    }

    if (obj.__typename === typeCondition) {
      return true;
    }

    // XXX here we reach an issue - we don't know if this fragment should match or not. It's either:
    // 1. A fragment on a non-matching concrete type or interface or union
    // 2. A fragment on a matching interface or union
    // If it's 1, we don't want to return anything, if it's 2 we want to match. We can't tell the
    // difference, so we warn the user, but still try to match it (backcompat).
    warnOnceInDevelopment(
      `You are using the simple (heuristic) fragment matcher, but your queries contain union or interface types.
     Apollo Client will not be able to able to accurately map fragments.` +
        `To make this error go away, use the IntrospectionFragmentMatcher as described in the docs: ` +
        `http://dev.apollodata.com/react/initialization.html#fragment-matcher`,
      'error',
    );

    context.returnPartialData = true;
    return true;
  }