text: """test the inspection registry system."""
  
  from sqlalchemy import Column
  from sqlalchemy import inspect
  from sqlalchemy import Integer
  from sqlalchemy import MetaData
  from sqlalchemy import Table
  from sqlalchemy.sql import ClauseElement
  from sqlalchemy.testing import fixtures
  from sqlalchemy.testing import is_
  
  
  class TestCoreInspection(fixtures.TestBase):
      def test_table(self):
          t = Table("t", MetaData(), Column("x", Integer))
  
          is_(inspect(t), t)
          assert t.is_selectable
          is_(t.selectable, t)
  
      def test_select(self):
          t = Table("t", MetaData(), Column("x", Integer))
          s = t.select()
  
          is_(inspect(s), s)
          assert s.is_selectable
          is_(s.selectable, s)
  
      def test_column_expr(self):
          c = Column("x", Integer)
          is_(inspect(c), c)
          assert not c.is_selectable
          assert not hasattr(c, "selectable")
  
      def test_no_clause_element_on_clauseelement(self):
          # re [ticket:3802], there are in the wild examples
          # of looping over __clause_element__, therefore the
          # absence of __clause_element__ as a test for "this is the clause
          # element" must be maintained
  
          class Foo(ClauseElement):
              pass
  
          assert not hasattr(Foo(), "__clause_element__")
  
      def test_col_now_has_a_clauseelement(self):
  
          x = Column("foo", Integer)
  
          assert hasattr(x, "__clause_element__")
  