test exit code with csh

if available, because csh exit codes can differ from sh/bash

IPython/core/tests/test_interactiveshell.py

@@ -25,9 +25,12 b' from os.path import join'
 import nose.tools as nt
 
 from IPython.core.inputtransformer import InputTransformer
-from IPython.testing.decorators import skipif, skip_win32, onlyif_unicode_paths
+from IPython.testing.decorators import (
+    skipif, skip_win32, onlyif_unicode_paths, onlyif_cmds_exist,
+)
 from IPython.testing import tools as tt
 from IPython.utils import io
+from IPython.utils.process import find_cmd
 from IPython.utils import py3compat
 from IPython.utils.py3compat import unicode_type, PY3
 
@@ -445,6 +448,18 b' class ExitCodeChecks(tt.TempFileMixin):'
         self.system("%s %s" % (sys.executable, self.fname))
         self.assertEqual(ip.user_ns['_exit_code'], -signal.SIGALRM)
 
+    @onlyif_cmds_exist("csh")
+    def test_exit_code_signal_csh(self):
+        SHELL = os.environ.get('SHELL', None)
+        os.environ['SHELL'] = find_cmd("csh")
+        try:
+            self.test_exit_code_signal()
+        finally:
+            if SHELL is not None:
+                os.environ['SHELL'] = SHELL
+            else:
+                del os.environ['SHELL']
+
 class TestSystemRaw(unittest.TestCase, ExitCodeChecks):
     system = ip.system_raw