# `Mutalisk`
[🔗](https://github.com/lukaszsamson/mutalisk/blob/v0.1.0/lib/mutalisk.ex#L1)

Public runtime helpers for Mutalisk.

Most users interact with Mutalisk through `mix mut`. This module exists for
diagnostics, tests, and advanced integrations that need to inspect or set the
active mutant id in the current BEAM.

The active id is stored in VM-global `:persistent_term`. If you set it
manually in tests or tools, use `try ... after Mutalisk.clear() end` so the
mutated state does not leak to other processes in the same VM.

# `active_key`

```elixir
@spec active_key() :: term()
```

Returns the `:persistent_term` key used to store the active mutant id.

Instrumented code reads this key to decide whether to execute original or
mutated code. Normal users should prefer `get_active/0`.

# `clear`

```elixir
@spec clear() :: :ok
```

Clears the active mutant id from `:persistent_term`.

After clearing, `get_active/0` returns `0` again for every process in the VM.

# `get_active`

```elixir
@spec get_active() :: non_neg_integer()
```

Returns the active mutant id for the current BEAM.

The default is `0`, meaning no mutant is active. The value is VM-global, not
process-local.

# `set_active`

```elixir
@spec set_active(non_neg_integer()) :: :ok
```

Sets the active mutant id for the current BEAM.

Passing `0` selects the original, unmutated behavior. Mutant worker processes
set this automatically; direct calls are primarily useful in diagnostics and
focused tests.

This writes VM-global `:persistent_term`, so every instrumented module in the
VM observes the new id until another `set_active/1` call or `clear/0`.

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*Consult [api-reference.md](api-reference.md) for complete listing*