diff --git a/src/Config.php b/src/Config.php
index 1ae4c77ee3..d4210c74e3 100644
--- a/src/Config.php
+++ b/src/Config.php
@@ -207,6 +207,22 @@ public function __get($name)
             throw new RuntimeException("ERROR: unable to get value of property \"$name\"");
         }
 
+        // Figure out what the terminal width needs to be for "auto".
+        if ($name === 'reportWidth' && $this->settings[$name] === 'auto') {
+            if (function_exists('shell_exec') === true) {
+                $dimensions = shell_exec('stty size 2>&1');
+                if (is_string($dimensions) === true && preg_match('|\d+ (\d+)|', $dimensions, $matches) === 1) {
+                    $this->settings[$name] = (int) $matches[1];
+                }
+            }
+
+            if ($this->settings[$name] === 'auto') {
+                // If shell_exec wasn't available or didn't yield a usable value, set to the default.
+                // This will prevent subsequent retrievals of the reportWidth from making another call to stty.
+                $this->settings[$name] = self::DEFAULT_REPORT_WIDTH;
+            }
+        }
+
         return $this->settings[$name];
 
     }//end __get()
@@ -229,13 +245,9 @@ public function __set($name, $value)
 
         switch ($name) {
         case 'reportWidth' :
-            // Support auto terminal width.
-            if ($value === 'auto' && function_exists('shell_exec') === true) {
-                $dimensions = shell_exec('stty size 2>&1');
-                if (is_string($dimensions) === true && preg_match('|\d+ (\d+)|', $dimensions, $matches) === 1) {
-                    $value = (int) $matches[1];
-                    break;
-                }
+            if (is_string($value) === true && $value === 'auto') {
+                // Nothing to do. Leave at 'auto'.
+                break;
             }
 
             if (is_int($value) === true) {
@@ -246,6 +258,7 @@ public function __set($name, $value)
                 $value = self::DEFAULT_REPORT_WIDTH;
             }
             break;
+
         case 'standards' :
             $cleaned = [];
 
diff --git a/tests/Core/AbstractMethodUnitTest.php b/tests/Core/AbstractMethodUnitTest.php
index 4d4f546995..50dd63ac69 100644
--- a/tests/Core/AbstractMethodUnitTest.php
+++ b/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
 {
@@ -45,9 +46,22 @@ abstract class AbstractMethodUnitTest extends TestCase
      */
     public static function setUpBeforeClass()
     {
-        $config            = new Config();
-        $config->standards = ['PSR1'];
+        /*
+         * 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 a usable value to circumvent Config trying to find a phpcs.xml config file.
+        self::setStaticConfigProperty('overriddenDefaults', ['standards' => ['PSR1']]);
+
+        // 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();
         $ruleset = new Ruleset($config);
 
         // Default to a file with the same name as the test class. Extension is property based.
@@ -74,9 +88,33 @@ public static function tearDownAfterClass()
     {
         self::$phpcsFile = null;
 
+        // Reset the static properties in the Config class to their defaults to prevent tests influencing each other.
+        self::setStaticConfigProperty('overriddenDefaults', []);
+        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('PHP_CodeSniffer\Config', $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.
      *