`urlRoot` in `karma.conf.js` can't be set to anything other than the default `/`

从 karma.conf.js 和 ng test 入口开始，使用所示的 urlRoot 配置重现故障。跟踪自定义上下文文件在 urlRoot 设置为 newBase 时如何解析 context.js，并将其与预期的 /karma/context.js 路径进行比较。当测试运行在配置的 urlRoot 下请求上下文脚本且不出现 404 时，即表示完成。

🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
• update
• lint
• extract-i18n
• run
• config
• help
• version
• doc

Is this a regression?

No.

Description

Can't set urlRoot in karma.conf.js to anything other than "/" because:

Angular CLI uses custom context file, which leads to this bug. It adds <base href="/">, which forces context.html to request http://localhost:9876/context.js instead of http://localhost:9876/karma/context.js.

which is described in detail in this issue: https://github.com/karma-runner/karma/issues/3357#issuecomment-634630974.

🔬 Minimal Reproduction

Run ng test with a karma.conf.js that contains a urlRoot set to anything but /:

{
    ...,
    urlRoot: "newBase"
}

🔥 Exception or Error

The error that is logged is the following:

09 11 2021 23:25:29.766:WARN [web-server]: 404: /_karma_webpack_/context.js

🌍 Your Environment

Angular CLI: 11.2.0
Node: 14.18.0
OS: darwin x64

Angular: 11.2.14
... common, compiler, compiler-cli, core, forms, localize
... platform-browser, platform-browser-dynamic, router, upgrade
Ivy Workspace: Yes

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.1102.0
@angular-devkit/build-angular   0.1102.0
@angular-devkit/core            11.2.14
@angular-devkit/schematics      11.2.14
@angular/animations             12.2.8
@angular/cdk                    11.2.13
@angular/cli                    11.2.0
@schematics/angular             11.2.14
@schematics/update              0.1102.0
rxjs                            6.6.7
typescript                      4.1.6