- changed test class naming for easier copying and searching of classes
- made base tests abstract and made MySQL an equal citisen in the test
hierarchie
- added missing db specific test classes
Basic implementation proposal for yiisoft/yii2#2022
Shortcomings/todo's:
* filtering on non-scalars (where IN statements) not supported
* Numeric properties with a corresponding validation rule will yield
errors when they contain an alphanumeric operator. These properties'
rules should be defined as 'string' or 'safe'.
* no implementation example in Gii code (yet).
close#8505
