Adding helper for fetching mock EntityManager in AbstractUnitTest
Updating tests for ExactMatchFilter so it does not rely on the container
Updating FilterCollection tests so they do not rely on the service container
Adding AbstractFilterTestCase which adds some helper methods for filter class tests
Updating tests for OrderByFilter so it does not rely on the container
Updating tests for SearchFilter so it does not rely on the container
Adding helper in AbstractUnitTest to fetch a mock session
Updating tests for flash message Provider so it does not rely on the container
Fixing dependencies for PreferenceLoader
Adding setter for ID in Preference entity
Updating PreferenceLoader tests so they are not container aware
Removing unused "use" statement
Making tests for UserProvider non container aware
Making AuthenticationHandler tests non container aware
Making KernelExceptionListener tests non container aware
Making AttributeFormTypeGuesser tests non container aware
Improving test coverage for UserProvider
Improving test coverage for flash Provider
Improving test coverage for UserManager
Some minor fixes in User entity, adding missing tests