Properly set up theme directory

phpunit/wp-theme-json-test.php

@@ -7,6 +7,35 @@
 
 class WP_Theme_Json_Test extends WP_UnitTestCase {
 
+	public function set_up() {
+		parent::set_up();
+		$this->theme_root = realpath( __DIR__ . '/data/themedir1' );
+
+		$this->orig_theme_dir = $GLOBALS['wp_theme_directories'];
+
+		// /themes is necessary as theme.php functions assume /themes is the root if there is only one root.
+		$GLOBALS['wp_theme_directories'] = array( WP_CONTENT_DIR . '/themes', $this->theme_root );
+
+		add_filter( 'theme_root', array( $this, 'filter_set_theme_root' ) );
+		add_filter( 'stylesheet_root', array( $this, 'filter_set_theme_root' ) );
+		add_filter( 'template_root', array( $this, 'filter_set_theme_root' ) );
+		$this->queries = array();
+		// Clear caches.
+		wp_clean_themes_cache();
+		unset( $GLOBALS['wp_themes'] );
+	}
+
+	public function tear_down() {
+		$GLOBALS['wp_theme_directories'] = $this->orig_theme_dir;
+		wp_clean_themes_cache();
+		unset( $GLOBALS['wp_themes'] );
+		parent::tear_down();
+	}
+
+	public function filter_set_theme_root() {
+		return $this->theme_root;
+	}
+
 	/**
 	 * Test that it reports correctly themes that have a theme.json.
 	 *