Refactor test class hierarchy and naming.

Renamed `MainTest` to `TestBase` and made it abstract to better reflect its role as a base class. Updated derived test classes (`CachePSR16MainTest` and `CachePSR6MainTest`) to extend `TestBase` and renamed them for consistency.

Author: byjg

tests/CachePSR16MainTest.php renamed to tests/CachePSR16Test.php

@@ -9,7 +9,7 @@
 use ByJG\Cache\Psr16\NoCacheEngine;
 use PHPUnit\Framework\Attributes\DataProvider;
 
-class CachePSR16MainTest extends MainTest
+class CachePSR16Test extends TestBase
 {
     /**
      * @param BaseCacheEngine $cacheEngine

tests/CachePSR6MainTest.php renamed to tests/CachePSR6Test.php

@@ -8,7 +8,7 @@
 use PHPUnit\Framework\Attributes\DataProvider;
 use Psr\SimpleCache\InvalidArgumentException;
 
-class CachePSR6MainTest extends MainTest
+class CachePSR6Test extends TestBase
 {
     /**
      * @param BaseCacheEngine $cacheEngine

tests/MainTest.php renamed to tests/TestBase.php

@@ -13,7 +13,7 @@
 use ByJG\Cache\Psr16\TmpfsCacheEngine;
 use PHPUnit\Framework\TestCase;
 
-class MainTest extends TestCase
+abstract class TestBase extends TestCase
 {
     /**
      * @var BaseCacheEngine|null