new_contents: from i8c.tests import TestCase
  
  SOURCE = """\
  define test::externals_test returns int
      extern ptr a_symbol
      extern func int, int (ptr) a_function
      call
      return
  """
  
  class TestExternals(TestCase):
      def test_externals(self):
          """Check that externals work."""
          tree, output = self.compile(SOURCE)
          self.assertEqual(["GNU_i8call"], output.operations)
  
subject: Add a basic check for externals