The TempTestEnv library helps with host testing. A temporary environment is set up to isolate tests which work with the process global environment. This is for testing convenience only, it is not a secure sandbox by any means.
When working on TempTestEnv lib, consider using:
$ fx set [...] --with-host //src/lib/testing/temp_test_env:tests
Unit tests can be run with:
$ fx test temp_test_env_lib_test