Angular Karma无法加载浏览器启动器

我已经完成了所有步骤（据我所知）：

karma.conf.js

npm install karma-firefox-launcher --save-dev

\node\u modules\karma firefox启动器\

按预期出现

package.json

plugins: [
  require('karma-jasmine'),
  require('karma-firefox-launcher'),
  require('karma-ie-launcher'),
  require('karma-jasmine-html-reporter'),
  require('karma-coverage-istanbul-reporter'),
  require('@angular-devkit/build-angular/plugins/karma')
],

注意：我对启动IE浏览器没有问题

这会不会是一个误导性的错误，真正的问题是Karma找不到Firefox.exe

plugins: [
  require('karma-jasmine'),
  require('karma-firefox-launcher'),
  require('karma-ie-launcher'),
  require('karma-jasmine-html-reporter'),
  require('karma-coverage-istanbul-reporter'),
  require('@angular-devkit/build-angular/plugins/karma')
],

  "devDependencies": {

    "karma-firefox-launcher": "^1.1.0",