adjust install tests

script/test-gem-installation

@@ -50,24 +50,17 @@ describe gemspec.full_name do
   let(:commonmarker_include_dir) { File.join(commonmarker_ext_dir, "include") }
 
   # representative sample of the files
-  let(:commonmarker_header_files) { ["commonmarker.h"] }
-  let(:packaged_library_header_files) { ["comrak_ffi.h"] }
+  let(:commonmarker_files) { ["Cargo.toml"] }
 
   it "loads the same version as the spec we've loaded" do
     assert_equal(Commonmarker::VERSION, gemspec.version.to_s)
   end
 
   describe "cruby" do
-    it "installs commonmarker headers" do
-      commonmarker_header_files.each do |header|
-        assert(File.file?(File.join(commonmarker_ext_dir, header)),
-          "expected #{header} to be installed in #{commonmarker_ext_dir}")
-
-        found = false
-        headers_dirs.each do |header_dir|
-          found = true if File.file?(File.join(header_dir, "commonmarker.h"))
-        end
-        assert(found, "expected to find commonmarker.h in one of: #{headers_dirs.inspect}")
+    it "installs commonmarker files" do
+      commonmarker_cargo_toml.each do |file|
+        assert(File.file?(File.join(commonmarker_ext_dir, file)),
+          "expected #{file} to be installed in #{commonmarker_ext_dir}")
       end
     end
   end