diff --git a/test/feed_reader/language_test.exs b/test/feed_reader/language_test.exs
index a9aa2a2..557be75 100644
--- a/test/feed_reader/language_test.exs
+++ b/test/feed_reader/language_test.exs
@@ -7,7 +7,43 @@ defmodule FeedReader.LanguageTest do
     assert is_atom(FeedReader.Language.detect(text))
   end
 
+  test "stops adding list entries after the detection limit" do
+    text = String.duplicate("This is English text. ", 2_000)
+
+    assert is_atom(FeedReader.Language.detect([text, "This entry is ignored."]))
+  end
+
   test "ignores non-text values when building a detection sample" do
     assert FeedReader.Language.detect([nil, 123]) == :en
   end
+
+  test "detects English from plain text" do
+    text = "The quick brown fox jumps over the lazy dog."
+
+    assert FeedReader.Language.detect(text) == :en
+  end
+
+  test "detects Portuguese from text and ignores markup" do
+    text = "<p>Este é um texto em português com palavras suficientes para detectar o idioma.</p>"
+
+    assert FeedReader.Language.detect(text) == :pt
+  end
+
+  test "combines binary list entries and skips non-text values" do
+    texts = [nil, "Este é um texto em português", 42, " com palavras suficientes para detectar."]
+
+    assert FeedReader.Language.detect(texts) == :pt
+  end
+
+  test "falls back to English for empty and unsupported input" do
+    assert FeedReader.Language.detect([]) == :en
+    assert FeedReader.Language.detect("") == :en
+    assert FeedReader.Language.detect(%{}) == :en
+  end
+
+  test "falls back to English when the detector exits on invalid UTF-8" do
+    ExUnit.CaptureLog.capture_log(fn ->
+      assert FeedReader.Language.detect(<<0xFF>>) == :en
+    end)
+  end
 end