diff --git a/classes/ComicPressDBInterface.inc b/classes/ComicPressDBInterface.inc
index b86de6b..3fb4789 100644
--- a/classes/ComicPressDBInterface.inc
+++ b/classes/ComicPressDBInterface.inc
@@ -12,12 +12,30 @@ class ComicPressDBInterface {
 
 	function _get_categories_to_exclude($categories = null) {
 		if (is_array($categories)) {
-			return array_diff(get_all_category_ids(), $categories);
+			return array_values(array_diff(get_all_category_ids(), $categories));
 		} else {
 			return array();
 		}
 	}
 
+	function _prepare_wp_query() {
+		global $wp_query;
+
+		$this->is_single = $wp_query->is_single;
+		$this->in_the_loop = $wp_query->in_the_loop;
+
+		$wp_query->is_single = $wp_query->in_the_loop = true;
+	}
+
+	function _reset_wp_query() {
+		global $wp_query;
+
+		$wp_query->is_single = $this->is_single;
+		$wp_query->in_the_loop = $this->in_the_loop;
+	}
+
+	// @codeCoverageIgnoreStart
+
 	/**
 	 * Find the terminal post in a specific category.
 	 */
@@ -73,22 +91,6 @@ class ComicPressDBInterface {
 		return empty($result) ? false : $result;
 	}
 
-	function _prepare_wp_query() {
-		global $wp_query;
-
-		$this->is_single = $wp_query->is_single;
-		$this->in_the_loop = $wp_query->in_the_loop;
-
-		$wp_query->is_single = $wp_query->in_the_loop = true;
-	}
-
-	function _reset_wp_query() {
-		global $wp_query;
-
-		$wp_query->is_single = $this->is_single;
-		$wp_query->in_the_loop = $this->in_the_loop;
-	}
-
 	/**
 	 * Get the previous comic from the current one.
 	 */
@@ -98,6 +100,8 @@ class ComicPressDBInterface {
 	 * Get the next comic from the current one.
 	 */
 	function get_next_post($categories = null, $override_post = null) { return $this->get_adjacent_post($categories, true, $override_post); }
+
+	// @codeCoverageIgnoreEnd
 }
 
 ?>
diff --git a/test/ComicPressDBInterfaceTest.php b/test/ComicPressDBInterfaceTest.php
index ff84e40..77d010d 100644
--- a/test/ComicPressDBInterfaceTest.php
+++ b/test/ComicPressDBInterfaceTest.php
@@ -5,6 +5,14 @@ require_once('PHPUnit/Framework.php');
 require_once('ComicPressDBInterface.inc');
 
 class ComicPressDBInterfaceTest extends PHPUnit_Framework_TestCase {
+	function setUp() {
+		global $wp_query;
+
+		_reset_wp();
+
+		unset($wp_query);
+	}
+
   function testSingleton() {
     $a = ComicPressDBInterface::get_instance();
     $this->assertTrue(!isset($a->test));
@@ -14,6 +22,64 @@ class ComicPressDBInterfaceTest extends PHPUnit_Framework_TestCase {
     $b = ComicPressDBInterface::get_instance();
     $this->assertEquals("test", $b->test);
   }
+
+  function providerTestGetCategoriesToExclude() {
+  	return array(
+  		array(null, array()),
+  		array(array(), array(1,2,3)),
+  		array(array(1), array(2,3)),
+  	);
+  }
+
+  /**
+   * @dataProvider providerTestGetCategoriesToExclude
+   */
+  function testGetCategoriesToExclude($input, $expected_output) {
+  	add_category(1, (object)array('slug' => 'one'));
+  	add_category(2, (object)array('slug' => 'one'));
+   	add_category(3, (object)array('slug' => 'one'));
+
+   	$dbi = new ComicPressDBInterface();
+
+   	$this->assertEquals($expected_output, $dbi->_get_categories_to_exclude($input));
+  }
+
+  function testPrepareWPQuery() {
+  	global $wp_query;
+
+  	$dbi = new ComicPressDBInterface();
+
+  	$wp_query = (object)array(
+  		'is_single' => false,
+  		'in_the_loop' => false
+  	);
+
+  	$dbi->_prepare_wp_query();
+
+  	$this->assertTrue($wp_query->is_single);
+  	$this->assertTrue($wp_query->in_the_loop);
+  	$this->assertTrue(false === $dbi->is_single);
+  	$this->assertTrue(false === $dbi->in_the_loop);
+  }
+
+  function testResetWPQuery() {
+  	global $wp_query;
+
+  	$dbi = new ComicPressDBInterface();
+
+  	$wp_query = (object)array(
+  		'is_single' => true,
+  		'in_the_loop' => true
+  	);
+
+  	$dbi->is_single = false;
+  	$dbi->in_the_loop = false;
+
+  	$dbi->_Reset_wp_query();
+
+  	$this->assertTrue(false === $wp_query->is_single);
+  	$this->assertTrue(false === $wp_query->in_the_loop);
+  }
 }
 
 ?>