Index: tests/phpunit/tests/customize/manager.php
===================================================================
--- tests/phpunit/tests/customize/manager.php	(revision 40141)
+++ tests/phpunit/tests/customize/manager.php	(working copy)
@@ -58,6 +58,13 @@
 		require_once( ABSPATH . WPINC . '/class-wp-customize-manager.php' );
 		$this->manager = $this->instantiate();
 		$this->undefined = new stdClass();
+
+		$orig_file = DIR_TESTDATA . '/images/canola.jpg';
+		$this->test_file = '/tmp/canola.jpg';
+		copy( $orig_file, $this->test_file );
+		$orig_file2 = DIR_TESTDATA . '/images/waffles.jpg';
+		$this->test_file2 = '/tmp/waffles.jpg';
+		copy( $orig_file2, $this->test_file2 );
 	}
 
 	/**
@@ -318,8 +325,7 @@
 		add_theme_support( 'custom-header' );
 		add_theme_support( 'custom-background' );
 
-		$canola_file = DIR_TESTDATA . '/images/canola.jpg';
-		$existing_canola_attachment_id = self::factory()->attachment->create_object( $canola_file, 0, array(
+		$existing_canola_attachment_id = self::factory()->attachment->create_object( $this->test_file, 0, array(
 			'post_mime_type' => 'image/jpeg',
 			'post_type' => 'attachment',
 			'post_name' => 'canola',
@@ -383,13 +389,13 @@
 					'post_title' => 'Waffles',
 					'post_content' => 'Waffles Attachment Description',
 					'post_excerpt' => 'Waffles Attachment Caption',
-					'file' => DIR_TESTDATA . '/images/waffles.jpg',
+					'file' => $this->test_file2,
 				),
 				'canola' => array(
 					'post_title' => 'Canola',
 					'post_content' => 'Canola Attachment Description',
 					'post_excerpt' => 'Canola Attachment Caption',
-					'file' => DIR_TESTDATA . '/images/canola.jpg',
+					'file' => $this->test_file,
 				),
 			),
 			'options' => array(