Add check_complete test for exit.

Co-Authored-By: Nicholas Bollweg <[e-mail]>

IPython/core/tests/test_inputtransformer2.py

@@ -215,6 +215,8 b' def test_check_complete():'
     nt.assert_equal(cc("def a():\n x=1\n global x"), ('invalid', None))
     nt.assert_equal(cc("a \\ "), ('invalid', None))  # Nothing allowed after backslash
     nt.assert_equal(cc("1\\\n+2"), ('complete', None))
+    nt.assert_equal(cc("1\\\n+2"), ('complete', None))
+    nt.assert_equal(cc("exit"), ('complete', None))
 
     example = dedent("""
         if True: