What do you mean by that exactly?
The builds and tests can’t depend on external sources comming from the network or user input: all dependencies and inputs must be specified before running the entire vm. But any nondeterminism in tests or builds (e.g. tests depending on local time or randomness or concurrency) will be deterministinc since the VM emulator is deterministic: providing mock functions for randomness and time, also linearization of multiple threads is done deterministically so all builds and tests will provide the same outputs for the same inputs, with no special requirements from the users.