diff --git a/imageapi_optimize.services.yml b/imageapi_optimize.services.yml
index b666988..0703436 100644
--- a/imageapi_optimize.services.yml
+++ b/imageapi_optimize.services.yml
@@ -5,3 +5,5 @@ services:
   imageapi_optimize.hooks:
     class: Drupal\imageapi_optimize\ImageAPIOptimizeHookImplementations
     arguments: ['@string_translation']
+  imageapi_optimize.shell_operations:
+    class: Drupal\imageapi_optimize\ShellOperations
diff --git a/src/ImageAPIOptimizeProcessorBinaryBase.php b/src/ImageAPIOptimizeProcessorBinaryBase.php
index 4f83c18..efbe021 100644
--- a/src/ImageAPIOptimizeProcessorBinaryBase.php
+++ b/src/ImageAPIOptimizeProcessorBinaryBase.php
@@ -6,6 +6,7 @@ use Drupal\Core\File\FileSystemInterface;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Image\ImageFactory;
 use Drupal\Core\Image\ImageInterface;
+use Drupal\iamgeapi_optimize\ImageAPIOptimizeShellOperationsInterface;
 use Psr\Log\LoggerInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
@@ -22,12 +23,20 @@ abstract class ImageAPIOptimizeProcessorBinaryBase extends ConfigurableImageAPIO
   protected $fileSystem;
 
   /**
+   * The imageapi shell operation service.
+   *
+   * @var \Drupal\imageapi_optimize\ImageAPIOptimizeShellOperationsInterface
+   */
+  protected $shellOperations;
+
+  /**
    * {@inheritdoc}
    */
-  public function __construct(array $configuration, $plugin_id, $plugin_definition, LoggerInterface $logger, ImageFactory $image_factory, FileSystemInterface $file_system) {
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, LoggerInterface $logger, ImageFactory $image_factory, FileSystemInterface $file_system, ImageAPIOptimizeShellOperationsInterface $shell_operatons) {
     parent::__construct($configuration, $plugin_id, $plugin_definition, $logger, $image_factory);
 
     $this->fileSystem = $file_system;
+    $this->shellOperations = $shell_operatons;
   }
 
   /**
@@ -40,7 +49,8 @@ abstract class ImageAPIOptimizeProcessorBinaryBase extends ConfigurableImageAPIO
       $plugin_definition,
       $container->get('logger.factory')->get('imageapi_optimize'),
       $container->get('image.factory'),
-      $container->get('file_system')
+      $container->get('file_system'),
+      $container->get('imageapi_optimize.shell_operations')
     );
   }
 
@@ -106,13 +116,7 @@ abstract class ImageAPIOptimizeProcessorBinaryBase extends ConfigurableImageAPIO
     if (is_null($executable)) {
       $executable = $this->executableName();
     }
-    $output = array();
-    $return_var = 0;
-    $path = exec('which ' . escapeshellarg($executable), $output, $return_var);
-    if ($return_var == 0) {
-      return $path;
-    }
-    return FALSE;
+    return $this->shellOperations->findExecutablePath($executable);
   }
 
   /**
@@ -129,18 +133,7 @@ abstract class ImageAPIOptimizeProcessorBinaryBase extends ConfigurableImageAPIO
    *   Returns TRUE if the command completed successfully, FALSE otherwise.
    */
   protected function execShellCommand($command, $options, $arguments) {
-    $output = array();
-    $return_val = 0;
-    $option_string = implode(' ', $options);
-    $argument_string = implode(' ', array_map('escapeshellarg', $arguments));
-    $last_line = exec(escapeshellcmd($command) . ' ' . $option_string . ' ' . $argument_string, $output, $return_val);
-
-    if ($return_val == 0) {
-      return TRUE;
-    }
-    else {
-      return FALSE;
-    }
+    return $this->shellOperations->execShellCommand($command, $options, $arguments);
   }
 
   /**
@@ -157,20 +150,7 @@ abstract class ImageAPIOptimizeProcessorBinaryBase extends ConfigurableImageAPIO
   }
 
   protected function saveCommandStdoutToFile($cmd, $dst) {
-    $return_val = 0;
-    ob_start();
-    passthru($cmd);
-    $output = ob_get_contents();
-    ob_end_clean();
-
-    file_unmanaged_save_data($output, $dst, FILE_EXISTS_REPLACE);
-
-    if ($return_val == 0) {
-      return TRUE;
-    }
-    else {
-      return FALSE;
-    }
+    return $this->shellOperations->saveCommandStdoutToFile($cmd, $dst);
   }
 
   public function getFullPathToBinary() {
diff --git a/src/ImageAPIOptimizeShellOperationsInterface.php b/src/ImageAPIOptimizeShellOperationsInterface.php
new file mode 100644
index 0000000..49e617b
--- /dev/null
+++ b/src/ImageAPIOptimizeShellOperationsInterface.php
@@ -0,0 +1,9 @@
+<?php
+
+namespace Drupal\iamgeapi_optimize;
+
+interface ImageAPIOptimizeShellOperationsInterface {
+  public function findExecutablePath($executable = NULL);
+  public function execShellCommand($command, $options, $arguments);
+  public function saveCommandStdoutToFile($cmd, $dst);
+}
diff --git a/src/ShellOperations.php b/src/ShellOperations.php
new file mode 100644
index 0000000..cbed5b8
--- /dev/null
+++ b/src/ShellOperations.php
@@ -0,0 +1,76 @@
+<?php
+
+namespace Drupal\imageapi_optimize;
+
+
+/**
+ * Storage controller class for "image optimize pipeline" configuration entities.
+ */
+class ShellOperations implements ImageAPIOptimizeShellOperationsInterface {
+
+  /**
+   * Search the local system for the given executable binary.
+   *
+   * @param null $executable
+   *   The name of the executable binary to find on the local system. If not
+   *   specified the default executeable name for this class will be used.
+   *
+   * @return string|false
+   *   The path to the binary on the local system, or FALSE if it could not be
+   *   located.
+   */
+  public function findExecutablePath($executable = NULL) {
+    $output = array();
+    $return_var = 0;
+    $path = exec('which ' . escapeshellarg($executable), $output, $return_var);
+    if ($return_var == 0) {
+      return $path;
+    }
+    return FALSE;
+  }
+
+  /**
+   * Execute a shell command on the local system.
+   *
+   * @param $command
+   *   The command to execute.
+   * @param $options
+   *   An array of options for the command. This will not be escaped before executing.
+   * @param $arguments
+   *   An array of arguments for the command. These will be escaped.
+   *
+   * @return bool
+   *   Returns TRUE if the command completed successfully, FALSE otherwise.
+   */
+  public function execShellCommand($command, $options, $arguments) {
+    $output = array();
+    $return_val = 0;
+    $option_string = implode(' ', $options);
+    $argument_string = implode(' ', array_map('escapeshellarg', $arguments));
+    $last_line = exec(escapeshellcmd($command) . ' ' . $option_string . ' ' . $argument_string, $output, $return_val);
+
+    if ($return_val == 0) {
+      return TRUE;
+    }
+    else {
+      return FALSE;
+    }
+  }
+
+  public function saveCommandStdoutToFile($cmd, $dst) {
+    $return_val = 0;
+    ob_start();
+    passthru($cmd);
+    $output = ob_get_contents();
+    ob_end_clean();
+
+    file_unmanaged_save_data($output, $dst, FILE_EXISTS_REPLACE);
+
+    if ($return_val == 0) {
+      return TRUE;
+    }
+    else {
+      return FALSE;
+    }
+  }
+}
diff --git a/tests/src/Unit/Drupal/Tests/imageapi_optimize/Unit/AdvDefTest.php b/tests/src/Unit/Drupal/Tests/imageapi_optimize/Unit/AdvDefTest.php
new file mode 100644
index 0000000..8290b95
--- /dev/null
+++ b/tests/src/Unit/Drupal/Tests/imageapi_optimize/Unit/AdvDefTest.php
@@ -0,0 +1,54 @@
+<?php
+
+namespace Drupal\Tests\imageapi_optimize\Unit;
+
+use Drupal\Tests\UnitTestCase;
+use Drupal\imageapi_optimize\Plugin\ImageAPIOptimizeProcessor\AdvDef;
+
+/**
+ * Tests AdvDef image optimize plugin.
+ *
+ * @group imageapi_optimize
+ */
+class AdvDefTest extends UnitTestCase {
+  function testCase() {
+    $this->assertTrue(TRUE);
+
+
+
+    // Make some mocks.
+    $config = [];
+    $loggerMock = $this->getMock('\Psr\Log\LoggerInterface');
+    $imageFactoryMock = $this->getMockBuilder('\Drupal\Core\Image\ImageFactory')
+      ->disableOriginalConstructor()
+      ->getMock();
+    $fileSystemMock = $this->getMock('\Drupal\Core\File\FileSystemInterface');
+    $shellOperationsMock = $this->getMockBuilder('\Drupal\iamgeapi_optimize\ImageAPIOptimizeShellOperationsInterface')
+      ->setMethods(['findExecutablePath', 'execShellCommand'])
+      ->getMock();
+
+    // Load up the plugin.
+    $advdef = new AdvDef($config, 'advdef', [], $loggerMock, $imageFactoryMock, $fileSystemMock, $shellOperationsMock);
+
+    $this->assertArrayHasKey('recompress', $advdef->defaultConfiguration());
+    $this->assertArrayHasKey('mode', $advdef->defaultConfiguration());
+
+    $shellOperationsMock->method('findExecutablePath')->will($this->returnArgument(0));
+    $fileSystemMock->method('realpath')->will($this->returnArgument(0));
+
+    $imagePNGMock = $this->getMock('\Drupal\Core\Image\ImageInterface');
+    $imagePNGMock->method('getMimeType')->willReturn('image/png');
+    $imageFactoryMock->method('get')->willReturn($imagePNGMock);
+
+    $shellOperationsMock->expects($this->once())
+      ->method('execShellCommand')
+      ->with(
+        $this->equalTo('advdef'),
+        $this->identicalTo(['--quiet', '--recompress', '-3']),
+        $this->identicalTo(['public://test_image.png'])
+      );
+
+    $advdef->applyToImage('public://test_image.png');
+
+  }
+}