Isolated Component Test

This is a test of the launch_component_in_nested_environment function in fuchsia_app. Its goal is to ensure the following:

• A nested environment is successfully created.
• The add_proxy_service function successfully proxies a loader for the new environment, allowing components to be launched.
• Components can be brought up in the nested environment.
• Components inside the nested environment only have access to the specific set of services granted by their parent, and cannot access other services within their parents' environment. Services added to the nested environment must also be visible to the components inside the nested environment.

The test ensures this by running three separate components.

• fuchsia_app_test_outer_component simulates the “outer world”. It runs fuchsia_app_test_middle_component in a nested environment containing EchoExposedByParent and EchoHiddenByParent, each of which echos a number and returns it to the client.
• fuchsia_app_test_middle_component simulates a parent component attempting to create an isolated child. After confirming that it can successfully access EchoExposedByParent and EchoHiddenByParent, it launches fuchsia_app_test_inner_component in a nested environment that only has access to EchoExposedByParent, which has been overridden to always return ‘42’.
• fuchsia_app_test_inner_componnent simulates the isolated child component. It confirms that it can't access EchoHiddenByParent and that EchoExposedByParent has been successfully overwritten, always returning ‘42’.