HeaderMatch: Add test

Library/Homebrew/test/livecheck/strategy/header_match_spec.rb

@@ -0,0 +1,16 @@
+# typed: false
+# frozen_string_literal: true
+
+require "livecheck/strategy/header_match"
+
+describe Homebrew::Livecheck::Strategy::HeaderMatch do
+  subject(:header_match) { described_class }
+
+  let(:url) { "https://www.example.com/" }
+
+  describe "::match?" do
+    it "returns true for any URL" do
+      expect(header_match.match?(url)).to be true
+    end
+  end
+end