More solid way to stick with npm instead of yarn

appveyor.yml

@@ -5,7 +5,7 @@ environment:
     - nodejs_version: '6'
 
   # stick to npm
-  PHENOMIC_TEST_WITH_YARN: 0
+  PHENOMIC_TEST_WITH_YARN: false
 
 version: "{build}"
 build: off

circle.yml

@@ -2,6 +2,10 @@ machine:
   node:
     version: 6
 
+  environment:
+    # stick to npm
+    PHENOMIC_TEST_WITH_YARN: false
+
 dependencies:
   override:
     - npm prune

docs/content/contributing/index.md

@@ -2,32 +2,56 @@
 title: How to contribute to Phenomic
 ---
 
+## Clone the repository & get dependencies
+
+```
+git clone https://github.com/MoOx/phenomic.git
+cd phenomic
+```
+
+**Note about dependencies:**
+We support both [npm](http://npmjs.com/) and [Yarn](http://yarnpkg.com/)
+but to make developer experience faster we use yarn by default.
+Some scripts use yarn under the hood. To force npm usage, just export this in
+your current terminal session:
+
+```console
+export PHENOMIC_TEST_WITH_YARN=false
+```
+
 ## Update the phenomic-theme-base
 
 To work on the phenomic-theme-base, run the following:
 
-```sh
+```console
 npm run phenomic-theme-base-start
 ```
+
 _or with `yarn`_
-```sh
+
+```console
 yarn run phenomic-theme-base-start
 ```
 
-Then you can edit files in the `phenomic-theme-base` folder.
+Then you can edit files in the `themes/phenomic-theme-base` folder, you should
+see change immediately.
 
 ## Update the docs
 
 To work on the docs, run the following:
-```sh
+
+```console
 npm run docs-start
 ```
+
 _or with `yarn`_
-```sh
+
+```console
 yarn run docs-start
 ```
 
-Then you can edit files in the `docs` folder.
+Then you can edit files in the `docs` folder and you will get changes
+immediately.
 
 ## Work on the core
 
@@ -36,13 +60,11 @@ Then you can edit files in the `docs` folder.
 - Integration tests are located at the root of the project (`__tests__/*`).
 
 _After every modification, please run the entire test suite by using
-`npm test`._
-_or with `yarn`_
-`yarn test`._
+`npm test` (or with `yarn`, using `yarn test`)._
 
 Note that the full test suite can take a few minutes, as it runs unit tests and
-integration tests (with several builds, including docs and a new project from
-the phenomic-theme-base).
+end to end tests
+(with several builds, including docs and a new project from the phenomic-theme-base).
 
 To speed things up, you can limit tests to the specific component you are working on.
 
@@ -53,11 +75,12 @@ Tests will be in ``src/PageContainer/__tests__/*``.
 
 To run tests for the ``PageContainer`` component:
 
-```sh
-ava src/PageContainer/__tests__/*
+```console
+jest src/PageContainer/__tests__/*
 ```
 
-When you think you are done with your update, remember to run either `npm test` or `yarn test`.
+When you think you are done with your update, remember to run either `npm test` (or `yarn test`).
+
 Anyway, CI will warn us if something goes wrong.
 
 ---

scripts/utils/test-folder.js

@@ -27,7 +27,12 @@ export default async function test(
   try {
     const targetModules = `${ target }/node_modules`
 
-    let yarn = process.env.PHENOMIC_TEST_WITH_YARN || true
+    let yarn = (
+      typeof process.env.PHENOMIC_TEST_WITH_YARN !== "undefined"
+      ? Boolean(JSON.parse(process.env.PHENOMIC_TEST_WITH_YARN))
+      : true
+    )
+
     if (yarn) {
       try {
         await exec("yarn --version")