我正在开发一个角度应用程序，当我运行“ng test”命令时，它显示一些错误并显示“已断开连接（0 次），因为 30000 毫秒内没有消息”。'。我尝试更新 karma、jasmine 软件包并执行“npm install”，但仍然没有任何帮助。这里是依赖包和karma.conf.js文件。我在这里错过了什么吗？需要什么套餐升级吗？
"devDependencies": {
"@angular-devkit/build-angular": "~0.13.0",
"@angular/animations": "^5.0.0",
"@angular/cli": "~7.3.2",
"@angular/compiler-cli": "~7.2.0",
"@angular/language-service": "~7.2.0",
"@types/jasmine": "~2.8.8",
"@types/jasminewd2": "~2.0.3",
"@types/node": "~8.9.4",
"codelyzer": "~4.4.2",
"husky": "^0.13.4",
"jasmine-core": "^2.5.2",
"jasmine-spec-reporter": "~4.2.1",
"karma": "^3.1.4",
"karma-chrome-launcher": "^2.2.0",
"karma-coverage-istanbul-reporter": "~2.0.1",
"karma-jasmine": "^1.1.2",
"karma-jasmine-html-reporter": "^0.2.2",
"protractor": "~5.4.0",
"ts-node": "~7.0.0",
"tslint": "~5.11.0",
"typescript": "~3.2.2",
"typescript-formatter": "^7.2.2",
"webpack": "^4.9.2"
},
module.exports = function (config) {
config.set({
basePath: '',
frameworks: ['jasmine', '@angular-devkit/build-angular'],
plugins: [
require('karma-jasmine'),
require('karma-chrome-launcher'),
require('karma-jasmine-html-reporter'),
require('karma-coverage-istanbul-reporter'),
require('@angular-devkit/build-angular/plugins/karma')
],
client: {
clearContext: false …我在应用程序中定义一个管道示例，它将大写字符串转换为小写字符串，例如：'Activities' => 'activities '。数据采用数组格式，我将此过滤器应用于*ngFor. 它返回一个错误，提示“toLowerString不是函数”，请帮助我理解哪里出错了。