使用 Nodeunit 测试

问题

假如你正在使用CoffeeScript并且想要验证功能是否与预期一致，便可以决定使用Nodeunit测试框架。

讨论

Nodeunit是一种JavaScript对于单元测试库（ Unit Testing libraries ）中xUnit族的实现，Java, Python, Ruby, Smalltalk中均可以使用。

当使用xUnit族测试框架时，你需要将所需测试的描述预期功能的代码写在一个文件中。

例如，我们希望计算器可以进行加法和减法，并且对于正负数均可以正确计算，测试如下：

# test/calculator.test.coffee
Calculator = require '../calculator'
exports.CalculatorTest =
    'test can add two positive numbers': (test) ->
        calculator = new Calculator
        result = calculator.add 2, 3
        test.equal(result, 5)
        test.done()

    'test can handle negative number addition': (test) ->
        calculator = new Calculator
        result = calculator.add -10, 5
        test.equal(result,  -5)
        test.done()

    'test can subtract two positive numbers': (test) ->
        calculator = new Calculator
        result = calculator.subtract 10, 6
        test.equal(result, 4)
        test.done()

    'test can handle negative number subtraction': (test) ->
        calculator = new Calculator
        result = calculator.subtract 4, -6
        test.equal(result, 10)
        test.done()

安装 Nodeunit

在可以运行你的测试之前，你必须先安装Nodeunit：

首先创建一个package.json文件

{
  "name": "calculator",
  "version": "0.0.1",
  "scripts": {
    "test": "./node_modules/.bin/nodeunit test"
  },
  "dependencies": {
    "coffee-script": "~1.4.0",
    "nodeunit": "~0.7.4"
  }
}

接下来从一个终端运行。

$ npm install

运行测试

使用代码行可以简便地运行测试文件：

$ npm test

测试失败，因为我们并没有calculator.coffee

suki@Yuzuki:nodeunit_testing (master)$ npm test
npm WARN package.json calculator@0.0.1 No README.md file found!

> calculator@0.0.1 test /Users/suki/tmp/nodeunit_testing
> ./node_modules/.bin/nodeunit test

/Users/suki/tmp/nodeunit_testing/node_modules/nodeunit/lib/nodeunit.js:72
        if (err) throw err;
                       ^
Error: ENOENT, stat '/Users/suki/tmp/nodeunit_testing/test'
npm ERR! Test failed.  See above for more details.
npm ERR! not ok code 0

创建一个简单文件

# calculator.coffee

class Calculator

module.exports = Calculator

并且重新运行测试套件。

suki@Yuzuki:nodeunit_testing (master)$ npm test
npm WARN package.json calculator@0.0.1 No README.md file found!

> calculator@0.0.1 test /Users/suki/tmp/nodeunit_testing
> ./node_modules/.bin/nodeunit test

calculator.test
✖ CalculatorTest - test can add two positive numbers

TypeError: Object #<Calculator> has no method 'add'
  ...

✖ CalculatorTest - test can handle negative number addition

TypeError: Object #<Calculator> has no method 'add'
  ...

✖ CalculatorTest - test can subtract two positive numbers

TypeError: Object #<Calculator> has no method 'subtract'
  ...

✖ CalculatorTest - test can handle negative number subtraction

TypeError: Object #<Calculator> has no method 'subtract'
  ...

FAILURES: 4/4 assertions failed (31ms)
npm ERR! Test failed.  See above for more details.
npm ERR! not ok code 0

通过测试

对方法进行实现来观察测试是否可以通过。

# calculator.coffee

class Calculator

  add: (a, b) ->
    a + b

  subtract: (a, b) ->
    a - b

module.exports = Calculator

当重新运行测试时可以看到全部通过：

suki@Yuzuki:nodeunit_testing (master)$ npm test
npm WARN package.json calculator@0.0.1 No README.md file found!

> calculator@0.0.1 test /Users/suki/tmp/nodeunit_testing
> ./node_modules/.bin/nodeunit test

calculator.test
✔ CalculatorTest - test can add two positive numbers
✔ CalculatorTest - test can handle negative number addition
✔ CalculatorTest - test can subtract two positive numbers
✔ CalculatorTest - test can handle negative number subtraction

OK: 4 assertions (27ms)

重构测试

既然测试全部通过，我们应看一看我们的代码或测试是否可以被重构。

在我们的测试文件中，每个测试都创建了自己的calculator实例。这会使我们的测试相当的重复，特别是对于大型的测试套件。理想情况下，我们应该考虑将初始化代码移动到每次测试之前运行。

通常在其他的xUnit库中，Nodeunit会提供一个setUp（以及tearDown）功能会在测试前调用。

Calculator = require '../calculator'

exports.CalculatorTest =

    setUp: (callback) ->
        @calculator = new Calculator
        callback()

    'test can add two positive numbers': (test) ->
        result = @calculator.add 2, 3
        test.equal(result, 5)
        test.done()

    'test can handle negative number addition': (test) ->
        result = @calculator.add -10, 5
        test.equal(result,  -5)
        test.done()

    'test can subtract two positive numbers': (test) ->
        result = @calculator.subtract 10, 6
        test.equal(result, 4)
        test.done()

    'test can handle negative number subtraction': (test) ->
        result = @calculator.subtract 4, -6
        test.equal(result, 10)
        test.done()

重新运行测试仍可全部通过。