Swap base class instead of redefinign the tearDown method

IPython/core/tests/test_interactiveshell.py

@@ -546,11 +546,8 b' class ExitCodeChecks(tt.TempFileMixin):'
             else:
                 del os.environ['SHELL']
 
-    def tearDown(self):
-        tt.TempFileMixin.tearDown(self)
-
 
-class TestSystemRaw(unittest.TestCase, ExitCodeChecks):
+class TestSystemRaw(ExitCodeChecks, unittest.TestCase):
     system = ip.system_raw
 
     @onlyif_unicode_paths
@@ -570,16 +567,10 b' class TestSystemRaw(unittest.TestCase, ExitCodeChecks):'
                       "keyboard interrupt from subprocess.call")
         self.assertEqual(ip.user_ns['_exit_code'], -signal.SIGINT)
 
-    def tearDown(self):
-        ExitCodeChecks.tearDown(self)
-
 # TODO: Exit codes are currently ignored on Windows.
-class TestSystemPipedExitCode(unittest.TestCase, ExitCodeChecks):
+class TestSystemPipedExitCode(ExitCodeChecks, unittest.TestCase):
     system = ip.system_piped
 
-    def tearDown(self):
-        ExitCodeChecks.tearDown(self)
-
     @skip_win32
     def test_exit_code_ok(self):
         ExitCodeChecks.test_exit_code_ok(self)
@@ -592,7 +583,7 b' class TestSystemPipedExitCode(unittest.TestCase, ExitCodeChecks):'
     def test_exit_code_signal(self):
         ExitCodeChecks.test_exit_code_signal(self)
 
-class TestModules(unittest.TestCase, tt.TempFileMixin):
+class TestModules(tt.TempFileMixin, unittest.TestCase):
     def test_extraneous_loads(self):
         """Test we're not loading modules on startup that we shouldn't.
         """
@@ -604,9 +595,6 b' class TestModules(unittest.TestCase, tt.TempFileMixin):'
         out = "False\nFalse\nFalse\n"
         tt.ipexec_validate(self.fname, out)
 
-    def tearDown(self):
-        tt.TempFileMixin.tearDown(self)
-
 class Negator(ast.NodeTransformer):
     """Negates all number literals in an AST."""
     def visit_Num(self, node):

IPython/core/tests/test_shellapp.py

@@ -24,12 +24,9 b" sqlite_err_maybe = dec.module_not_available('sqlite3')"
 SQLITE_NOT_AVAILABLE_ERROR = ('WARNING: IPython History requires SQLite,'
                               ' your history will not be saved\n')
 
-class TestFileToRun(unittest.TestCase, tt.TempFileMixin):
+class TestFileToRun(tt.TempFileMixin, unittest.TestCase):
     """Test the behavior of the file_to_run parameter."""
 
-    def tearDown(self):
-        tt.TempFileMixin.tearDown(self)
-
     def test_py_script_file_attribute(self):
         """Test that `__file__` is set when running `ipython file.py`"""
         src = "print(__file__)\n"