Improve snake_case automatic recommendation for underscore followed b…

…y capital letter (#347)

Fixes #334

lib/elixir_analyzer/exercise_test/common_checks/variable_names.ex

@@ -75,7 +75,9 @@ defmodule ElixirAnalyzer.ExerciseTest.CommonChecks.VariableNames do
   end
 
   defp to_snake_case(name) do
-    # Macro.underscore is good enough because a module attribute name must be a valid Elixir identifier anyway
-    Macro.underscore(to_string(name))
+    name
+    |> to_string()
+    |> Macro.underscore()
+    |> String.replace(~r/_+/, "_")
   end
 end

test/elixir_analyzer/exercise_test/common_checks/variable_names_test.exs

@@ -442,6 +442,27 @@ defmodule ElixirAnalyzer.ExerciseTest.CommonChecks.VariableNamesTest do
                 }}
              ]
     end
+
+    test "it should report a violation /19" do
+      code =
+        quote do
+          defmodule CredoSampleModule do
+            def some_function(parameter1, parameter2) do
+              %{some_value: some_Value, other_value: otherValue} = parameter1
+            end
+          end
+        end
+
+      assert VariableNames.run(code) == [
+               {:fail,
+                %Comment{
+                  type: :actionable,
+                  name: Constants.solution_variable_name_snake_case(),
+                  comment: Constants.solution_variable_name_snake_case(),
+                  params: %{expected: "some_value", actual: "some_Value"}
+                }}
+             ]
+    end
   end
 
   describe "unrelated code" do