基本但正确使用 beforeEach() 或 afterEach() 与 mocha.js 和 chai.js

Question

我想用mocha/chai测试与二叉搜索树相关的代码。在这里，我正在测试 public insert 方法。我想使用 beforeEach() and/or afterEach() 挂钩在每个 it() 语句之前重置测试环境，这样我就不必完全重复基础知识。但是，我不断收到各种错误。

规格

describe("BinarySearchTree insert function", function() {

  beforeEach(function() {
    var binarySearchTree = new BinarySearchTree();
    binarySearchTree.insert(5);
  });

  it("creates a root node with value equal to the first inserted value", function () {
    expect(binarySearchTree.root.value).to.equal(5);
  });

  it("has a size equal to the amount of inserted values", function () {
    binarySearchTree.insert(3);
    expect(binarySearchTree.size).to.equal(2);
  });

  it("returns an error for non-unique values", function () {
    binarySearchTree.insert(3);
    expect(binarySearchTree.insert(3)).to.throw(String);
  });

  it("if inserted value is larger than current node, make or descend to rightChild", function () {
    binarySearchTree.insert(3);
    binarySearchTree.insert(10);
    binarySearchTree.insert(7);
    expect(binarySearchTree.root.rightChild.value).to.equal(10);
  });

});

错误：ReferenceError: binarySearchTree is not defined

事实上，在没有afterEach()重置测试环境之前我就预料到了错误，而不是因为binarySearchTree没有定义。如果可能的话，我想只用 Mocha 和 Chai（而不是像 Sinon 等其他软件包）来完成这个。

测试代码

exports.Node = Node;

function Node(value) {
  this.value = value;
  this.leftChild = null;
  this.rightChild = null;
}

exports.BinarySearchTree = BinarySearchTree;

function BinarySearchTree() {
  this.root = null;
  this.size = 0;
}

BinarySearchTree.prototype.insert = function(value) {
  // 1) when root node is already instantiated
  if (this.root === null) {
    // tree is empty
    this.root = new Node(value);
    this.size++;
  } else {
  // 2) nodes are already inserted
    var findAndInsert = function (currentNode) {
      if (value === currentNode.value) {
        throw new Error('must be a unique value');
      }
      // base case
      if (value > currentNode.value) {
        // belongs in rightChild
        if (currentNode.rightChild === null) {
          currentNode.rightChild = new Node(value);
        } else {
          findAndInsert(currentNode.rightChild);
        }
      } else if (value < currentNode.value) {
        // belongs in leftChild
        if (currentNode.leftChild === null) {
          currentNode.leftChild = new Node(value);
        } else {
          findAndInsert(currentNode.leftChild);
        }
      }
    };
    findAndInsert(this.root);
    this.size++;
  }
};

奖金问题...我不确定我是否正确测试抛出的错误（当插入非唯一值时）？

Answer 1

未定义，因为它不在测试函数范围内。在描述范围之前定义它。作为参考，请查看 Angular 文档。 https://docs.angularjs.org/guide/unit-testing

describe("BinarySearchTree insert function", function() {
  var binarySearchTree;
  beforeEach(function() {
    binarySearchTree = new BinarySearchTree();
    binarySearchTree.insert(5);
  });

  it("creates a root node with value equal to the first inserted value", function () {
    expect(binarySearchTree.root.value).to.equal(5);
  });

  it("has a size equal to the amount of inserted values", function () {
    binarySearchTree.insert(3);
    expect(binarySearchTree.size).to.equal(2);
  });

  it("returns an error for non-unique values", function () {
    binarySearchTree.insert(3);
    expect(binarySearchTree.insert(3)).to.throw(String);
  });

  it("if inserted value is larger than current node, make or descend to rightChild", function () {
    binarySearchTree.insert(3);
    binarySearchTree.insert(10);
    binarySearchTree.insert(7);
    expect(binarySearchTree.root.rightChild.value).to.equal(10);
  });

});

Answer 2

你得到 binarySearchTree 的原因是 undefined 已经解释过了。

我想谈谈 beforeEach 和 afterEach 函数。

在 beforeEach 函数中，我们通常会进行基本设置以进行测试，例如变量初始化、停止外部调用等。

和 'afterEach' 方法的工作方式类似于 destroy 函数，通常我们在其中编写内存释放内容。

基本但正确使用 beforeEach() 或 afterEach() 与 mocha.js 和 chai.js

Basic but proper use of beforeEach() or afterEach() with mocha.js and chai.js

javascript

testing

mocha.js

chai