add tests

test/feed_reader/url_test.exs

@@ -0,0 +1,45 @@
+defmodule FeedReader.URLTest do
+  use ExUnit.Case, async: true
+
+  alias FeedReader.URL
+
+  test "returns nil for a missing URL" do
+    assert URL.resolve_root_relative(nil, ["https://example.com"]) == nil
+  end
+
+  test "returns absolute and other non-root-relative URLs unchanged" do
+    absolute = "https://cdn.example.com/story"
+
+    assert URL.resolve_root_relative(absolute, ["https://example.com"]) == absolute
+    assert URL.resolve_root_relative("story", ["https://example.com"]) == "story"
+  end
+
+  test "resolves a root-relative URL against the first absolute base" do
+    assert URL.resolve_root_relative("/story", ["relative", nil, "https://example.com/feed"]) ==
+             "https://example.com/story"
+  end
+
+  test "keeps a root-relative URL when no absolute base exists" do
+    assert URL.resolve_root_relative("/story", [nil, "relative", 123]) == "/story"
+  end
+
+  test "requires a list of bases for root-relative resolution" do
+    assert URL.resolve_root_relative("/story", nil) == "/story"
+    assert URL.resolve_root_relative("/story", "https://example.com") == "/story"
+  end
+
+  test "accepts only absolute bases with both a scheme and host" do
+    bases = [
+      "/relative",
+      "mailto:reader@example.com",
+      "https:///missing-host",
+      "https://example.com"
+    ]
+
+    assert URL.resolve_root_relative("/story", bases) == "https://example.com/story"
+  end
+
+  test "preserves the URL when URI parsing receives a non-binary base" do
+    assert URL.resolve_root_relative("/story", [42]) == "/story"
+  end
+end