Yeah, should be doable with sourceror, given the following plain elixir poc:
"""
defmodule MyApp.Test do
test "abc" do
y = 15
assert %{a: ^y, b: 8} = call()
end
end
"""
|> Code.string_to_quoted!(
literal_encoder: &{:ok, {:__block__, &2, [&1]}},
token_metadata: true,
unescape: false
)
|> Macro.postwalk(fn
{:assert, assert_meta, [{:=, assign_meta, [{:%{}, _, pairs}, call]}]} ->
checks =
Enum.map(pairs, fn {{:__block__, _meta, [key]}, value} ->
quote do
assert unquote(value) = response.unquote(key)
end
end)
{:__block__, [],
[
{:assert, assert_meta, [{:=, assign_meta, [Macro.var(:response, nil), call]}]} | checks
]}
other ->
other
end)
|> Code.quoted_to_algebra(
literal_encoder: &{:ok, {:__block__, &2, [&1]}},
token_metadata: true,
unescape: false
)
|> Inspect.Algebra.format(:infinity)
|> IO.iodata_to_binary()
|> IO.puts()
# defmodule MyApp.Test do
# test "abc" do
# y = 15
# (assert response = call()
# assert ^y = response.a
# assert 8 = response.b)
# end
# end
Not sure how to best get rid of the parenthesis for the block there though.
Sourceror should take care of the parens, no? Not actually sure. I guess not because we’re writing new code 
Removing them manually wouldn’t be the biggest deal considering the time-savings of code-rewriting (though I shouldn’t say that as it’s not my project we’re talking about).
