如何用磁带为测试节点或javascript编写自定义断言，或者检查子字符串而不是t.deepEquals()

Question

使用磁带，我如何编写一个自定义断言方法来代替t.equal（）？或者有没有一种测试断言方法可以检查子字符串，这样我测试的整个字符串就不必使用t.deepEqual（）进行逐字比较？

var test = require("tape")
test('messages contain key words', function (t) {
  // this is what I'm using:
  t.equal(MyEncode(Fruit).indexOf('eat more') > -1,true,'should contain "eat more"')
  // this is what I want:
  t.contains(myEncode(Fruit),'eat more','should contain "eat more"')
  t.end()
})

当我测试myEncode时，我可以看到字符串不包含子字符串，但我无法查看实际值，因为它的计算结果仅为false，这没有信息：

  not ok 1 should contain "eat more"
---
  operator: equal
  expected: true
  actual:   false
  at: checkCmd (/test.js:63:11)
...

通过阅读上面的测试输出，我不知道我的测试是不是限制性太强，还是输出实际上不正确。相反，我希望看到myEncode返回的实际值，以加快查找问题的速度：

  not ok 2 should contain "eat more"
---
  operator: contains
  expected: "eat more"
  actual:   "Apples are allowed to be eaten on weekdays and weekends"
  at: checkCmd (/test.js:66:11)
...

Answer 1

多亏了github tape问题中的@mbstock示例测试方法，我才开始工作。如何定义新的测试方法#154.

要测试的函数，通常在另一个文件（例如appToTest.js）中

function brownFox(argument) {
    return "The "+argument+" fox jumped"
} 
exports.brownFox = brownFox

测试脚本：

// Test module typically named test.js
var test = require("tape")
var f = require("./appToTest")
// regular built-in test
test('String must match exactly', function (t) { // can be too specific
    t.deepEqual(f.brownFox('quick brown'), "The quick brown fox jumped") // should pass
    t.deepEqual(f.brownFox('quick black'), "The quick brown fox jumped") // will fail
    t.deepEqual(f.brownFox('quick white'), "The quick white fox jumped") // should pass
    t.comment('Strings must be fully specified to match word for word')
    t.end()
})
// It can be too tedious to maintain the test string to always 
// match exactly the string in the code being tested
// I don't care what the fox is as long as it jumped
// Since there is no "contains" test in tape, I hack t.equal()
test('String should contain a fox', function (t) {
    // does not show actual value when test fails; shows true or false instead
    // "jumped" must be tediously repeated to know what the test is about
    t.equal(f.brownFox('quick brown').indexOf("jumped") > -1, true, "contains jumped") // should pass
    t.equal(f.brownFox('quick black').indexOf("junped") > -1, true, "contains jumped") // should fail
    t.comment('failures are not descriptive')
    t.end()
})
// Using equal() can result in more time spent fixing or adjusting the test
// than coding the application
// So define your own tape test method
/////////////// Example of defining a custom tape test method
test.Test.prototype.stringContains = function(actual, contents, message) {
  this._assert(actual.indexOf(contents) > -1, {
    message: message || 'should contain '+contents,
    operator: 'stringContains',
    actual: actual,
    expected: contents
  });
};
/////////////// Example using a custom tape test method
test('String should contain a fox', function (t) {
    // shows actual value when test fails
    t.stringContains(f.brownFox('quick brown'), "jumped") // should pass
    t.stringContains(f.brownFox('quick brown'), "junped") // should fail
    // still supports custom message to override default message:
    t.stringContains(f.brownFox('quick brown'), "jumped", 'must contain "jumped"') // should pass
    t.stringContains(f.brownFox('quik white'), "jumped") // should pass
    t.comment('failures are more descriptive')
    t.end()
})

请注意，定制的测试输出现在报告"实际"字符串：

TAP version 13
# String must match exactly
ok 1 should be equivalent
not ok 2 should be equivalent
  ---
    operator: deepEqual
    expected: 'The quick brown fox jumped'
    actual:   'The quick black fox jumped'
    at: Test.<anonymous> (./tape-test.js:9:7)
  ...
ok 3 should be equivalent
# Strings must be fully specified to match word for word
# String should contain a fox
ok 4 contains jumped
not ok 5 contains jumped
  ---
    operator: equal
    expected: true
    actual:   false
    at: Test.<anonymous> (./tape-test.js:23:7)
  ...
# failures are not descriptive
# String should contain a fox
ok 6 should contain jumped
not ok 7 should contain junped
  ---
    operator: stringContains
    expected: 'junped'
    actual:   'The quick brown fox jumped'
    at: Test.test.Test.stringContains (./tape-test.js:33:8)
ok 8 must contain "jumped"
ok 9 should contain jumped
# failures are more descriptive
1..9
# tests 9
# pass  6
# fail  3

我安装了extend-tape，然后意识到我必须将其与babel一起使用，因为V8还不支持导入，但我不想添加babel作为依赖项。

由于上面的代码是有效的，所以我不认为使用extend-tape有什么意义。