运行测试用例时出现节点错误“无法找到模块”

I'm new to node and nightwatch and I have followed all the Getting Started instructions from Installing node, npm, selenium stand alone, starting the selenium driver, I downloaded the chrome driver as well and have it in the same directory. I have created the conf file and a simple test case js. When I go to run the test case through Node Command Line, I keep getting an error: I'm new to node and nightwatch and I have follo