Add Kino.start_child!/1

[jonatanklosko]

🐈

[josevalim]

Let’s steal the reason formatting from this function: https://github.com/elixir-lang/elixir/blob/v1.15.5/lib/ex_unit/lib/ex_unit/callbacks.ex#L568

:) probably worth adding a start_child! to Elixir itself.

[jonatanklosko]

ExUnit does {:start_spec, reason}, but I think it is confusing since it doesn't really have to do with the child spec itself:

** (RuntimeError) failed to start child with the spec Foo.
Reason: bad child specification, got: {:already_started, #PID<0.330.0>}

[josevalim]

Your call if you want to change it here. :)