doc: merge unit tests/docker unit tests pages, simplfy, reword

1 files changed, 48 insertions, 5 deletions

diff --git a/doc/md/Unit-tests.md b/doc/md/Unit-tests.md
index 651b546d..c45f957d 100644
--- a/doc/md/Unit-tests.md
+++ b/doc/md/Unit-tests.md
@@ -1,6 +1,6 @@
-### Setup your environment for tests
+The testing framework used is [PHPUnit](https://phpunit.de/); it can be installed with [Composer](https://getcomposer.org/), which is a dependency management tool.
 
-The framework used is [PHPUnit](https://phpunit.de/); it can be installed with [Composer](https://getcomposer.org/), which is a dependency management tool.
+## Setup a testing environment
 
 ### Install composer
 
@@ -10,7 +10,7 @@ You can either use:
 - a local version, downloadable [here](https://getcomposer.org/download/). To update a local composer installation, run `php composer.phar self-update`
 
 
-#### Install Shaarli dev dependencies
+### Install Shaarli development dependencies
 
 ```bash
 $ cd /path/to/shaarli
@@ -18,7 +18,7 @@ $ composer install
 $ composer update
 ```
 
-#### Install Xdebug
+### Install Xdebug
 
 Xdebug must be installed and enable for PHPUnit to generate coverage reports. See http://xdebug.org/docs/install.
 
@@ -36,7 +36,7 @@ Then add the following line to `/etc/php/php.ini`:
 zend_extension=xdebug.so
 ```
 
-#### Run unit tests
+## Run unit tests
 
 Run `make test` and ensure tests return `OK`. If tests return failures, refer to PHPUnit messages and fix your code/tests accordingly.
 
@@ -75,3 +75,46 @@ To run all tests annotated with `@group WIP`:
 ```bash
 $ vendor/bin/phpunit --group WIP tests/
 ```
+
+### Running tests inside Docker containers
+
+Test Dockerfiles are located under `tests/docker/<distribution>/Dockerfile`,
+and can be used to build Docker images to run Shaarli test suites under common
+Linux environments.
+
+Dockerfiles are provided for the following environments:
+
+- `alpine36` - [Alpine 3.6](https://www.alpinelinux.org/downloads/)
+- `debian8` - [Debian 8 Jessie](https://www.debian.org/DebianJessie) (oldstable)
+- `debian9` - [Debian 9 Stretch](https://wiki.debian.org/DebianStretch) (stable)
+- `ubuntu16` - [Ubuntu 16.04 Xenial Xerus](http://releases.ubuntu.com/16.04/) (LTS)
+
+What's behind the curtains:
+
+- each image provides:
+    - a base Linux OS
+    - Shaarli PHP dependencies (OS packages)
+    - test PHP dependencies (OS packages)
+    - Composer
+- the local workspace is mapped to the container's `/shaarli/` directory,
+- the files are rsync'd so tests are run using a standard Linux user account
+  (running tests as `root` would bypass permission checks and may hide issues)
+- the tests are run inside the container.
+
+To run tests inside a Docker container:
+
+```bash
+# build the Debian 9 Docker image for unit tests
+$ cd /path/to/shaarli
+$ cd tests/docker/debian9
+$ docker build -t shaarli-test:debian9 .
+
+# install/update 3rd-party test dependencies
+$ composer install --prefer-dist
+
+# run tests using the freshly built image
+$ docker run -v $PWD:/shaarli shaarli-test:debian9 docker_test
+
+# run the full test campaign
+$ docker run -v $PWD:/shaarli shaarli-test:debian9 docker_all_tests
+```