6. 使用 Mocha 编写测试 “Test Driven Development”

Mocha 是一个 js 测试的包, 编写测试有两个关键字 describe 和 it

• describe 是一个”统领块”, 所有的 test functions 都会在它”名下”
• it 表示每一个 test function

create_test.js

const assert = require('assert')
// assume we have a User model defined in src/user.js
const User = require('../src/user')

// after installing Mocha, we have global access
// to describe and it keywords
describe('Creating records', () => {
  it('saves a user', () => {
    const joe = new User({ name: "Joe" });
    joe.save();
    assert()
  });
});

7. NoSQL Databases

Benefits of NoSQL

• Easy for inserting and retrieving data, since they are contained in one block, in one json object
• Flexible schema, if a new attribute added, it is easy to just add / append to the object
• Scalability, horizontally partition the data (availability > consistency)
• Aggregation, find metrics and etc

Drawbacks of NoSQL

• Update = Delete + Insert, not built for update
• Not consistent, ACID is not guaranteed, do not support transactions
• Not read optimized. Read entire block find the attribute. But SQL, just need one column (read time compartively slow)
• Relations are not implicit
• JOINS are hard to accomplish, all manually