add Recovery.Encoding module

test/feed_reader/recovery/encoding_test.exs

@@ -0,0 +1,32 @@
+defmodule FeedReader.Recovery.EncodingTest do
+  use ExUnit.Case, async: true
+
+  alias FeedReader.Recovery.Encoding
+
+  test "passes UTF-8 input through unchanged" do
+    chunks = ["<title>", "café", "</title>"]
+
+    assert Encoding.transcode(chunks, :utf8) == chunks
+    assert Encoding.normalize_declaration(chunks, :utf8) == chunks
+  end
+
+  test "transcodes Latin-1 chunks to UTF-8" do
+    chunks = ["<title>caf", <<0xE9>>, "</title>"]
+
+    assert chunks |> Encoding.transcode(:latin1) |> Enum.join() == "<title>café</title>"
+  end
+
+  test "rewrites a Latin-1 declaration to UTF-8" do
+    chunks = ["<?xml version=\"1.0\" encoding=\"ISO-8859-1\"?>", "<rss/>"]
+
+    assert chunks |> Encoding.normalize_declaration(:latin1) |> Enum.join() ==
+             "<?xml version=\"1.0\" encoding=\"UTF-8\"?><rss/>"
+  end
+
+  test "rewrites declarations split across chunks" do
+    chunks = ["<?xml version=\"1.0\" enc", "oding=\"latin1\"?>", "<rss/>"]
+
+    assert chunks |> Encoding.normalize_declaration(:latin1) |> Enum.join() ==
+             "<?xml version=\"1.0\" encoding=\"UTF-8\"?><rss/>"
+  end
+end