I know I am joining the party quite late, but I have seen a way in which you can actually execute an alias with a given ENV set, without having to manually type “MIX_ENV=blabla” before the command.
You can do it like they do in ecto, use a test_with_env function that does a lot of dark magic 
:
defp aliases do
[
"test.all": ["test.unit", "test.integration"],
"test.unit": &run_unit_tests/1,
"test.integration": &run_integration_tests/1
]
end
def run_integration_tests(args), do: test_with_env("integration", args)
def run_unit_tests(args), do: test_with_env("test", args)
def test_with_env(env, args) do
args = if IO.ANSI.enabled?(), do: ["--color" | args], else: ["--no-color" | args]
IO.puts("==> Running tests with `MIX_ENV=#{env}`")
{_, res} =
System.cmd("mix", ["test" | args],
into: IO.binstream(:stdio, :line),
env: [{"MIX_ENV", to_string(env)}]
)
if res > 0 do
System.at_exit(fn _ -> exit({:shutdown, 1}) end)
end
end
You can read more about this in the blog:
Basically, the hardcore part is the command:
System.cmd("mix", ["test" | args],
into: IO.binstream(:stdio, :line),
env: [{"MIX_ENV", to_string(env)}]
)
Which executes a command at system level and executes the given command with any variable you pass it, setting the ENV explicitly but without you having to care about it.
A clever use of aliases IMHO.
