Index: tests/image/base.php
===================================================================
--- tests/image/base.php	(revision 1172)
+++ tests/image/base.php	(working copy)
@@ -30,4 +30,21 @@
 	public function setEngine( $editors ) {
 		return array( $this->editor_engine );
 	}
+
+	/**
+	 * Helper assertion for testing alpha on images
+	 * 
+	 * @param  string $image_path
+	 * @param  array $point      array(x,y)
+	 * @param  int $alpha
+	 */
+	protected function assertImageAlphaAtPoint( $image_path, $point, $alpha ) {
+
+		$im = imagecreatefrompng( $image_path );
+		$rgb = imagecolorat($im, $point[0], $point[1]);
+
+		$colors = imagecolorsforindex($im, $rgb);
+
+		$this->assertEquals( $alpha, $colors['alpha'] );
+	}
 }
Index: tests/image/editor_gd.php
===================================================================
--- tests/image/editor_gd.php	(revision 0)
+++ tests/image/editor_gd.php	(revision 0)
@@ -0,0 +1,57 @@
+<?php
+
+/**
+ * Test the WP_Image_Editor_GD class
+ * @group image
+ * @group media
+ */
+
+/**
+ * @todo how does one run this test on it's own without including the parent class?
+ */
+require_once( 'base.php' );
+
+class Tests_Image_Editor_GD extends WP_Image_UnitTestCase {
+	public $editor_engine = 'WP_Image_Editor_GD';
+
+	public function setup() {
+		require_once( ABSPATH . WPINC . '/class-wp-image-editor.php' );
+		require_once( ABSPATH . WPINC . '/class-wp-image-editor-gd.php' );
+		parent::setUp();
+	}
+
+	public function test_image_preserves_alpha_on_resize() {
+
+		$file = DIR_TESTDATA . '/images/transparent.png';
+
+		$editor = wp_get_image_editor( $file );
+		$editor->load();
+		$editor->resize(5,5);
+		$save_to_file = tempnam( get_temp_dir(), '' ) . '.png';
+		
+		$editor->save( $save_to_file );
+
+		$this->assertImageAlphaAtPoint( $save_to_file, array( 0,0 ), 127 );
+
+	}
+	
+	/**
+	 * Test the image created with WP_Image_Edior_GD preserves alpha with no resizing etc
+	 * 
+	 * 
+	 */
+	public function test_image_preserves_alpha() {
+
+		$file = DIR_TESTDATA . '/images/transparent.png';
+
+		$editor = wp_get_image_editor( $file );
+		$editor->load();
+
+		$save_to_file = tempnam( get_temp_dir(), '' ) . '.png';
+		
+		$editor->save( $save_to_file );
+
+		$this->assertImageAlphaAtPoint( $save_to_file, array( 0,0 ), 127 );
+	}
+
+}