Readme file for unit-testing

~dev_rating/application/tests/readme.md

+Instruction:
+
+1. Install composer
+2. (From app/system dir) Tools -> Add dependency -> phpunit/phpunit -> install
+3. Settings -> Composer -> Path to bootstrap: /grade-rating/~dev_rating/system/composer.json
+4. Go to any test from /app/tests folder
+5. Right mouse click -> Run
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