Function _throws

lib/assert.js:317–346

(shouldThrow, block, expected, message)

}

function _throws(shouldThrow, block, expected, message) {
  var actual;

  if (typeof expected === 'string') {
    message = expected;
    expected = null;
  }

  try {
    block();
  } catch (e) {
    actual = e;
  }

  message = (expected && expected.name ? ' (' + expected.name + ').' : '.') +
            (message ? ' ' + message : '.');

  if (shouldThrow && !actual) {
    fail('Missing expected exception' + message);
  }

  if (!shouldThrow && expectedException(actual, expected)) {
    fail('Got unwanted exception' + message);
  }

  if ((shouldThrow && actual && expected &&
      !expectedException(actual, expected)) || (!shouldThrow && actual)) {
    throw actual;
  }
}

// 11. Expected to throw an error:
// assert.throws(block, Error_opt, message_opt);