WIP: Test the elixir functions

.gitignore

@@ -23,4 +23,9 @@ erl_crash.dump
 id3-*.tar
 
 # Rustler creates native files inside /priv. We'll ignore that.
-/priv/native/*
+/priv/native/*
+
+native/id3/.cargo/config
+
+.DS_Store
+priv/.DS_Store

test/id3v2_test.exs

@@ -1,8 +1,55 @@
 defmodule ID3Test do
   use ExUnit.Case
-  doctest ID3
+  # doctest ID3
+  @path_to_sample_mp3 "priv/sample_mp3/WAKADINALI-Morio-Anzenza-Ft-Dyana-Cods.mp3"
 
-  test "greets the world" do
-    assert ID3.hello() == :world
+  describe "get_tag" do
+    test "get_tag!/1: return ID3_struct when valid mp3 path provided" do
+      assert %ID3.Tag{} = ID3.get_tag!(@path_to_sample_mp3)
+    end
+
+    test "get_tag/1: return {:ok, ID3_struct} when valid mp3 path provided" do
+      assert {
+               :ok,
+               %ID3.Tag{}
+             } = ID3.get_tag(@path_to_sample_mp3)
+    end
+
+    test "get_tag/1: return error tuple when invalid path provided" do
+      assert {:error, :file_open_error} = ID3.get_tag("")
+    end
+  end
+
+  describe "write_tag" do
+    test "write_tag/2" do
+      # get file with year: nil
+      assert {
+               :ok,
+               %ID3.Tag{
+                 year: nil
+               } = tag
+             } = ID3.get_tag(@path_to_sample_mp3)
+
+      # write tag year: 2020
+      ID3.write_tag(%{tag | year: 2020}, @path_to_sample_mp3)
+      # assert tag year: 2020
+      assert {
+               :ok,
+               %ID3.Tag{year: 2020} = tag
+             } = ID3.get_tag(@path_to_sample_mp3)
+
+      on_exit(fn ->
+        IO.puts(
+          "#{__MODULE__}.on_exit/1 cleaning up test: write_tag/2 -> resetting test file to initial tag"
+        )
+
+        ID3.write_tag(%{tag | year: nil}, @path_to_sample_mp3)
+
+        assert {
+                 :ok,
+                 %ID3.Tag{year: nil}
+               } = ID3.get_tag(@path_to_sample_mp3)
+      end)
+    end
   end
 end