function shouldThrow(func, errorMessage) { var errorThrown = false; var error = null; try { func(); } catch (e) { errorThrown = true; error = e; } if (!errorThrown) throw new Error('not thrown'); if (String(error) !== errorMessage) throw new Error(`bad error: ${String(error)}`); } shouldThrow(() => { Promise.race.call(() => { }, []); }, `TypeError: promise capability requires a constructor function`);