Test YARP.parse_file by using it in tests

Author: eregon

test/newline_test.rb

@@ -25,7 +25,7 @@ def visit(node)
       source = File.read(filepath, binmode: true, external_encoding: Encoding::UTF_8)
       expected = rubyvm_lines(source)
 
-      result = YARP.parse(source, relative)
+      result = YARP.parse_file(filepath)
       assert_empty result.errors
 
       result.mark_newlines