AbstractMethodUnitTest: take advantage of the change in reportWidth handling

For the tests using the `AbstractMethodUnitTest` class, the `reportWidth` and most other config settings are irrelevant.

This commit changes some of the set up/tear down for the test to make the use of the `Config` class more efficient.

This should make the tests using the `AbstractMethodUnitTest` class as their base significantly faster (at the very least on Windows).

While not benchmarked properly, I have done some comparisons with the test runs on my local machine on Windows.

* `phpunit --filter Core` (= the tests which use this base class + a few extra tests):
    Before: **2 minutes**.
    After: **8 seconds**.
* The same effect can be seen when running `phpunit` without a `--filter`:
    Before: **7 minutes**.
    After: **5 minutes**.
* And when I apply a similar change to the one made here to the base test class in PHPCSUtils (4621 tests):
    Before: **2.5 minutes**.
    After: **1 second**.

Author: jrfnl

tests/Core/AbstractMethodUnitTest.php

@@ -13,6 +13,7 @@
 use PHP_CodeSniffer\Ruleset;
 use PHP_CodeSniffer\Files\DummyFile;
 use PHPUnit\Framework\TestCase;
+use ReflectionProperty;
 
 abstract class AbstractMethodUnitTest extends TestCase
 {
@@ -45,7 +46,21 @@ abstract class AbstractMethodUnitTest extends TestCase
      */
     public static function setUpBeforeClass(): void
     {
-        $config            = new Config();
+        /*
+         * Set the static properties in the Config class to specific values for performance
+         * and to clear out values from other tests.
+         */
+
+        self::setStaticConfigProperty('executablePaths', []);
+
+        // Set to values which prevent the test-runner user's `CodeSniffer.conf` file
+        // from being read and influencing the tests. Also prevent an `exec()` call to stty.
+        self::setStaticConfigProperty('configData', ['report_width' => 80]);
+        self::setStaticConfigProperty('configDataFile', '');
+
+        $config = new Config();
+
+        // Set to a usable value to circumvent Config trying to find a phpcs.xml config file.
         $config->standards = ['PSR1'];
 
         $ruleset = new Ruleset($config);
@@ -74,9 +89,32 @@ public static function tearDownAfterClass(): void
     {
         self::$phpcsFile = null;
 
+        // Reset the static properties in the Config class to their defaults to prevent tests influencing each other.
+        self::setStaticConfigProperty('executablePaths', []);
+        self::setStaticConfigProperty('configData', null);
+        self::setStaticConfigProperty('configDataFile', null);
+
     }//end tearDownAfterClass()
 
 
+    /**
+     * Helper function to set the value of a private static property on the Config class.
+     *
+     * @param string $name  The name of the property to set.
+     * @param mixed  $value The value to set the property to.
+     *
+     * @return void
+     */
+    public static function setStaticConfigProperty($name, $value)
+    {
+        $property = new ReflectionProperty(Config::class, $name);
+        $property->setAccessible(true);
+        $property->setValue(null, $value);
+        $property->setAccessible(false);
+
+    }//end setStaticConfigProperty()
+
+
     /**
      * Get the token pointer for a target token based on a specific comment found on the line before.
      *