javascript - 正确使用 QUnit throw() 断言？

Question

使用 QUinit 的 throw()断言我想测试是否抛出错误以及错误消息。我有以下功能:

/**
 * Error function for Node.
 * @param {String} msg Error message.
 */
function NodeError (msg) {
  var that = this

  /**
   * Attribute for message.
   * @type {String}
   */
  this.msg = msg

  /**
   * Function rendering NodeError as a string.
   * @return {String} String representation of NodeError.
   */
  this.toString = function () {
    return that.msg
  }
}

/**
 * Node object. TODO Fill out.
 * @param {String} title Node title.
 * @throws {NodeError} If no title given
 */
function Node (title) {
  var that = this

  if (!title) {
    throw new Error('Error: no title given')
  }

  /**
   * Node title
   * @type {[type]}
   */
  this.title = title
}

以及以下QUnit测试:

QUnit.test('new Node w/o title throws error', function (assert) {
  assert.expect(1) // Expected number of assertions

  assert.throws(
    function () { new Node() },
    function (err) { err.toString() === 'Error: no title given' },
    'Error thrown'
  )
})

但是，单元测试失败了:

Error thrown@ 0 ms
Expected:   
function( a ){
  [code]
}
Result:     
Error("Error: no title given")
Diff:   
function( a ){
  [code]
}Error("Error: no title given")
Source:     
    at Object.<anonymous> (file:///Users/maasha/install/src/protwiz/test/test_pw_node.js:10:10)

要做什么？

Answer 1

传递给 assert.throws 的第二个函数应该返回一些东西。您当前有一个计算结果为 bool 值的语句，但结果被丢弃。该函数然后 returns implicitly, thus returning undefined 。

此外，您抛出的是 new Error(...)，而不是 NodeError。您要么需要更改它，要么只使用 err.message。

这是一个固定版本:

function NodeError (msg) {
  var that = this;
  this.msg = msg;
  this.toString = function () {
    return that.msg;
  }
}

function Node (title) {
  var that = this;

  if (!title) {
    throw new NodeError('Error: no title given'); // <- CHANGED
  }

  this.title = title;
}


QUnit.test('new Node w/o title throws error', function (assert) {
  assert.expect(1);

  assert.throws(
    function () { new Node(); },
    function (err) { return err.toString() === 'Error: no title given' },  // <- CHANGED
    'Error thrown'
  );
})

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您可能需要考虑使用 linting 工具，它可能会捕获此问题以及其他问题(例如，您有很多缺少分号，这可能会导致 unexpected results )。