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chore(test): Add, CONTRIBUTOR update (#3569)

* chore(test): Add, CONTRIBUTOR update. Adds a file to test directory to aid contributors in how to add tests.
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1 parent 8bc25f6 commit e8cb8757653e03a1c25014d9403f3f32d3a2515a @TheLarkInn TheLarkInn committed on GitHub Dec 27, 2016
Showing with 60 additions and 10 deletions.
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  2. +52 −0 test/
  3. +7 −9 test/TestCases.test.js
@@ -48,7 +48,7 @@ your pull request should be accepted quickly.
Some things that will increase the chance that your pull request is accepted:
-* Write tests
+* [Write tests](./test/
* Follow the existing coding style
* Write a [good commit message](
@@ -0,0 +1,52 @@
+# Welcome to the webpack test suite!!!!
+Every pull request that you submit to webpack (besides README and spelling corrections in comments) requires tests that are created.
+But don't give up hope!!! Although our tests may appear complex and overwhelming, once you become familiar with the test suite and structure, adding and creating tests will be fun and beneficial as you work inside the codebase! ❤
+## tl;dr
+* Clone repo
+* install and link deps
+ * `yarn install.`
+ * `npm run test` or `npm t`
+* To run an individual suite: (recommended during development for easier isolated diffs)
+Example: `$(npm bin)/mocha --grep ConfigTestCases`
+## Test suite overview
+We use MochaJS for our tests. For more information on Mocha you can visit their [homepage](!
+### Class Tests
+All test files can be found in *.test.js. There are many tests that simply test API's of a specific class/file (such as `Compiler`, `Errors`, Integration, `Parser`, `RuleSet`, Validation).
+If the feature you are contributing involves one of those classes, then best to start there to understand the structure.
+### xCases
+In addition to Class specific tests, there are also directories that end in "Cases". The suites for these cases also have corresponding *.test.js files.
+#### cases (`TestCases.test.js`) <sup>1</sup>
+Cases are a set of general purpose tests that will run against a variety of permutations of webpack configurations. When you are making a general purpose change that doesn't require you to have a special configuration, you would likely add your tests here. Inside of the `./test/cases` directory you will find tests are broken into thematic sub directories. Take a moment to explore the different options.
+To add a new case, create a new directory inside of the top level test groups, and then add an `index.js` file (and any other supporting files).
+By default this file will be the entry point for the test suite and you can add your `it()`'s there. This will also become bundled so that node env support happens as well.
+#### configCases (`ConfigTestCases.test.js`) <sup>1</sup>
+If you are trying to solve a bug which is reproducible when x and y properties are used together in a config, then configCases is the place to be!!!!
+In addition to an `index.js`, these configCases require a `webpack.config.js` is located inside of your test suite. This will run this specific config through `webpack` just as you were building individually. They will use the same loading/bundling technique of your `it()` tests, however you now have a more specific config use cases that you can write even before you start coding.
+#### statsCases (`Stats.test.js`)
+Stats cases are similar to configCases except specifically focusing on the `expected` output of your stats. Instead of writing to the console, however the output of stats will be written to disk.
+By default, the "expected" outcome is a pain to write by hand so instead when statsCases are run the following happens:
+* Checks for `expected.txt` file containing expected results.
+* If the `expected.txt` doesn't match what is output, then an `actual.txt` stats output file will be created and the test will fail. (A typical workflow for stats cases is to fail the test and copy the results from `actual.txt` to `expected.txt`.)
+* If the actual output matches `expected.txt`, the tests passes and you are free to submit that PR with pride!!!
+## Questions? Comments?
+If you are still nervous or don't quite understand, please submit an issue and tag us in it, and provide a relevant PR while working on!
+## Footnotes
+<sup>1</sup> webpack's parser supports the use of ES2015 features like arrow functions, harmony exports, etc. However as a library we follow NodeJS's timeline for dropping older versions of node. Because of this we expect your tests on Travis to pass all the way back to NodeJS v0.12; Therefore if you would like specific tests that use these features to be ignored if they are not supported, then you should add a `test.filter.js` file. This allows you to import the syntax needed for that test, meanwhile ignoring it on node versions (during CI) that don't support it. webpack has a variety of helpful exapmles you can refer to if you are just starting out. See the `./helpers` folder to find a list of the versions.
@@ -144,17 +144,15 @@ describe("TestCases", function() {
loader: "jade-loader"
- plugins: (config.plugins || []).concat(
- function() {
- this.plugin("compilation", function(compilation) {
- ["optimize", "optimize-modules-basic", "optimize-chunks-basic", "after-optimize-tree", "after-optimize-assets"].forEach(function(hook) {
- compilation.plugin(hook, function() {
- compilation.checkConstraints();
- });
+ plugins: (config.plugins || []).concat(function() {
+ this.plugin("compilation", function(compilation) {
+ ["optimize", "optimize-modules-basic", "optimize-chunks-basic", "after-optimize-tree", "after-optimize-assets"].forEach(function(hook) {
+ compilation.plugin(hook, function() {
+ compilation.checkConstraints();
- }
- )
+ });
+ })
webpack(options, function(err, stats) {
if(err) return done(err);

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