It's possible to test corner cases around HostEnsureCanCompileStrings from a browser or command line using tricks like those in tc39/ecma262 issue #1495:

<meta http-equiv="Content-Security-Policy" content="script-src 'nonce-test'">
<script nonce="test">
// Code to run with HostEnsureCanCompileStrings is false
</script>

or

$ npx node@10 --disallow_code_generation_from_strings -e '// Code to run'

Quite a few of these interactions could be tested if there was simply a way to get HostEnsureCanCompileStrings to throw for a particular testcase without breaking tests that assumes it returns normally like those under test/language/eval-code.

Even more interactions could be tested if it could be turned off only for particular values of calleeRealm.