Pass test: "opens file and writes each line to a list of strings"

(Remember that filepaths in Elixir projects are from the root and are not relative to the source code reading the file)

lib/day1/day1.ex

@@ -30,4 +30,13 @@ defmodule Day1 do
 
     {List.first(numbers), List.last(numbers)}
   end
+
+  def parse_file(file_path, return_type) do
+    case return_type do
+      :string ->
+        file_path
+        |> File.read!()
+        |> String.split("\n", trim: true)
+    end
+  end
 end

lib/day1/day1_test.exs

@@ -7,7 +7,7 @@ defmodule Day1Test do
   end
 
   test "opens file and writes each line to a list of strings" do
-    assert Day1.parse_file("test/day1_test.txt", :string) == [
+    assert Day1.parse_file("./lib/day1/mocks/lines_of_text.txt", :string) == [
              "first line of the file",
              "second line of the file",
              "third line of the file"