patch-package
--- a/node_modules/karma-safari-launcher/index.js
+++ b/node_modules/karma-safari-launcher/index.js
@@ -13,6 +13,11 @@ var SafariBrowser = function(baseBrowserDecorator) {
       var content = data.toString().replace('%URL%', url);
       var staticHtmlPath = self._tempDir + '/redirect.html';
 
+      var pathForMojave = path.join(process.env.HOME, 'Library/Containers/com.apple.Safari/Data/redirect.html');
+      if (fs.existsSync(pathForMojave)) {
+        staticHtmlPath = pathForMojave;
+      }
+
       fs.writeFile(staticHtmlPath, content, function(err) {
         self._execCommand(self._getCommand(), [staticHtmlPath]);
       });