Running ng test with --include fails for IE11

[ayonix]

🐞 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, I don't think so.

Description

ng test --browsers=IE --include=**/*.spec.ts fails to run.

When tsconfig is targeting es5 because of IE11 support, running ng test with the --include flag replaces the const context = require.context... through the single-test-transform-plugin. The replacement is not transpiled further and thus fails to run tests in IE11.
We are using angular11, but this is still the case for angular12.

🔬 Minimal Reproduction

• ng new test-ie
• add Angular routing? No
• Stylesheet? Css
• npm install karma-ie-launcher --save-dev
• remove not before IE11 in .browserslistrc
• add require('karma-ie-launcher'), in karma.conf.js
• set target to "es5" in tsconfig.json
• run ng test --browsers=IE --include="**/*.spec.ts"

🔥 Exception or Error

Browser:

SCRIPT1002: Syntaxerror
main.js (132,32)

Console:

IE 11.0 (Windows 10) ERROR
  Syntaxerror
  at http://localhost:9876/_karma_webpack_/main.js:132:32

🌍 Your Environment

$ ng version

     _                      _                 ____ _     ___
    / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
   / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
  / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
 /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
                |___/
    

Angular CLI: 12.0.5
Node: 16.3.0
Package Manager: npm 7.15.1
OS: win32 x64

Angular: 12.0.5
... animations, cli, common, compiler, compiler-cli, core, forms
... platform-browser, platform-browser-dynamic, router

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.1200.5
@angular-devkit/build-angular   12.0.5
@angular-devkit/core            12.0.5
@angular-devkit/schematics      12.0.5
@schematics/angular             12.0.5
rxjs                            6.6.7
typescript                      4.2.4

Anything else relevant?

Just happens with IE11.

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