Add instructions for running tests to README.md

README.md

@@ -23,3 +23,24 @@ Need even more info?
 Read our [wiki](https://github.com/wp-cli/wp-cli/wiki) and find out how to create your own commands with our [commands cookbook](https://github.com/wp-cli/wp-cli/wiki/Commands-Cookbook).
 
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+
+Running tests
+-------------
+
+The tests use PHPUnit, which can be installed using [composer](http://getcomposer.org/).
+Once you've composer installed, run:
+
+    composer.phar install --dev
+
+Before running the tests, you'll need a MySQL user called wp_cli_test with the password password1 that
+has full privileges on the MySQL database wp_cli_test. Running the following
+as root in MySQL should do the trick:
+
+    GRANT ALL PRIVILEGES ON wp_cli_test.* TO "wp_cli_test"@"localhost"
+    IDENTIFIED BY "password1";
+    
+Finally, to run the tests:
+
+    vendor/bin/phpunit tests
+
+