Add unit tests

[msmakouz]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	❌

Part of #22

[what-the-diff]

PR Summary

• Added and Enhanced Test Cases
  This PR introduced new test cases to CreateCommandTest.php, DownCommandTest.php, and GenerateCommandTest.php. These test cases will help ensure that our system operates as expected and immediately pinpoint any issues that may arise from changes.
• Unchanged Test File
  No changes were made to ListCommandTest.php, ensuring that the existing tests are still valid and relevant.
• Introduction of Test Case Class
  A PHPUnit test case class was introduced in a new file TestCase.php, which aids in creating uniform and reusable test sets.
• Enhancements to Existing Test Files
  Multiple existing test files were modified, such as UpCommandTest.php, EntityReaderTest.php, AllHandlerTest.php, and AnyHandlerTest.php. In particular, these enhancements included adding tests to ensure different scenarios and edge cases are thoroughly checked.
• New Test Files
  Several new test files were added, including ones for classes like FromConveyorSchemaProvider, CachedCollection, CachedCount, and EntityReader. This further broadens our test coverage and ensures all code units function as expected.
• New Filter Handlers Test
  Newly added files InHandlerTest.php and LikeHandlerTest.php in the tests/Unit/Data/Reader/FilterHandler directory will verify the functioning of these respective filter handlers.
• New Exception Test Files
  The PR added new test files NotFoundExceptionTest.php and NotInstantiableClassExceptionTest.php in the tests/Unit/Exception directory. These help check our system's response when encountering exceptions.
• Factory Class Test
  A new test file named DbalFactoryTest.php was introduced in the tests/Unit/Factory/DbalFactory directory to test the correctness and reliability of our factory class.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ea138b3) 84.53% compared to head (21ee51b) 93.55%.

Additional details and impacted files

@@             Coverage Diff              @@
##                2.0     #185      +/-   ##
============================================
+ Coverage     84.53%   93.55%   +9.01%     
  Complexity      375      375              
============================================
  Files            58       58              
  Lines          1009     1009              
============================================
+ Hits            853      944      +91     
+ Misses          156       65      -91     

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