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doc: improve testing guide

Add guide on choice of assertions, use of ES.Next features,
and the WPT upstream.

PR-URL: #11150
Ref: #11142
Reviewed-By: Rich Trott <>
Reviewed-By: Santiago Gimeno <>
Reviewed-By: James M Snell <>
Reviewed-By: Timothy Gu <>
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joyeecheung authored and italoacasas committed Feb 3, 2017
1 parent 803f6b3 commit abae26421e8ae70877148af4fb6dabdfb7f780fa
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  1. +55 −0 doc/guides/
@@ -209,6 +209,35 @@ const assert = require('assert');
const freelist = require('internal/freelist');
### Assertions
When writing assertions, prefer the strict versions:
* `assert.strictEqual()` over `assert.equal()`
* `assert.deepStrictEqual()` over `assert.deepEqual()`
When using `assert.throws()`, if possible, provide the full error message:
() => {
throw new Error('Wrong value');
/^Error: Wrong value$/ // Instead of something like /Wrong value/
### ES.Next features
For performance considerations, we only use a selected subset of ES.Next
features in JavaScript code in the `lib` directory. However, when writing
tests, it is encouraged to use ES.Next features that have already landed
in the ECMAScript specification. For example:
* `let` and `const` over `var`
* Template literals over string concatenation
* Arrow functions when appropriate
## Naming Test Files
Test files are named using kebab casing. The first component of the name is
@@ -220,3 +249,29 @@ For example, a test for the `beforeExit` event on the `process` object might be
named `test-process-before-exit.js`. If the test specifically checked that arrow
functions worked correctly with the `beforeExit` event, then it might be named
## Imported Tests
### Web Platform Tests
Some of the tests for the WHATWG URL implementation (named
`test-whatwg-url-*.js`) are imported from the
[Web Platform Tests Project](
These imported tests will be wrapped like this:
/* eslint-disable */
/* WPT Refs:
// Test code
/* eslint-enable */
If you want to improve tests that have been imported this way, please send
a PR to the upstream project first. When your proposed change is merged in
the upstream project, send another PR here to update Node.js accordingly.
Be sure to update the hash in the URL following `WPT Refs:`.

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