Add test for empty stylesheet argument

Author: xipasduarte

tests/phpunit/tests/theme/wpTheme.php

@@ -375,6 +375,17 @@ public function test_get_files_nonexistent_theme() {
 		$this->assertEmpty( $files );
 	}
 
+	/**
+	 * Test wp_customize_url with no $stylesheet argument.
+	 *
+	 * @ticket 63632
+	 *
+	 * @covers ::wp_customize_url
+	 */
+	public function test_wp_customize_url_no_stylesheet() {
+		$this->assertSame( esc_url( admin_url( 'customize.php' ) ), wp_customize_url() );
+	}
+
 	/**
 	 * Test wp_customize_url with no query args.
 	 *