Make running tests locally easier and documented

tests/README.md

@@ -0,0 +1,56 @@
+Unit Tests for [YOURLS](https://github.com/YOURLS/YOURLS/) [![Build Status](https://api.travis-ci.org/YOURLS/YOURLS-unit-tests.png?branch=master)](https://travis-ci.org/YOURLS/YOURLS) 
+=================
+
+
+About
+-----
+
+This is the unit test suite for YOURLS : a collection of hundreds of tests to make sure that whenever something in YOURLS is added, changed or removed, everything still works under all the supported PHP versions.
+
+Tests
+-----------
+If you want to run tests locally:
+
+0. Install PHPUnit
+1. Create an empty MySQL database and user. **Do not use an exisiting database** or you will lose data, guaranteed.  
+3. Copy `<YOURLS_ROOT>tests/data/config/yourls-tests-config-sample.php` to `<YOURLS_ROOT>/tests/yourls-tests-config.php` and edit it to match your setup.  
+4. In YOURLS root directory, you can now run the shell command:
+```bash
+$ phpunit
+```
+
+Hopefully you should see something like the following appear:
+
+```
+YOURLS installed, starting PHPUnit
+
+PHPUnit 7.5.20 by Sebastian Bergmann and contributors.
+
+Runtime:       PHP 7.4.3
+Configuration: D:\home\planetozh\ozh.in\phpunit.xml.dist
+
+...............................................................  63 / 519 ( 12%)
+............................................................... 126 / 519 ( 24%)
+............................................................... 189 / 519 ( 36%)
+............................................................... 252 / 519 ( 48%)
+............................................................... 315 / 519 ( 60%)
+............................................................... 378 / 519 ( 72%)
+............................................................... 441 / 519 ( 84%)
+............................................................... 504 / 519 ( 97%)
+...............                                                 519 / 519 (100%)
+
+Time: 6.06 seconds, Memory: 24.25Mb
+
+OK (519 tests, 1123 assertions)
+```
+
+You can elect to run only selected groups of tests, eg:
+
+```bash
+$ phpunit --group formatting
+```
+
+See each `@group` directive in selected tests.
+
+PHPUnit supports both `phpunit.xml` and `phpunit.xml.dist`, where `phpunit.xml` has higher priority:
+if you want to specify your own settings, copy `phpunit.xml.dist` to `phpunit.xml` and edit that file.

tests/includes/install.php

@@ -33,8 +33,9 @@ function yut_install_yourls() {
  */
 function yut_find_config() {
     $config_locations = array(
-        dirname(__DIR__). '/yourls-tests-config.php',         // manual, run locally
-        dirname(dirname(__DIR__)) . '/user/config.php',       // Travis, run from YOURLS/YOURLS
+        dirname(dirname(__DIR__)). '/yourls-tests-config.php',  // manual, run locally, config in YOURLS root
+        dirname(__DIR__). '/yourls-tests-config.php',           // manual, run locally, config in YOURLS/tests
+        dirname(dirname(__DIR__)) . '/user/config.php',         // Travis, run from YOURLS/YOURLS
     );
 
     foreach($config_locations as $config) {