Added test code for 'commenting out' feature of alias magic

IPython/core/tests/test_alias.py

@@ -38,4 +38,13 b' def test_alias_args_error():'
     with capture_output() as cap:
         _ip.run_cell('parts 1')
 
-    nt.assert_equal(cap.stderr.split(':')[0], 'UsageError')
  No newline at end of file
+    nt.assert_equal(cap.stderr.split(':')[0], 'UsageError')
+    
+def test_alias_args_commented():
+    """Check that alias correctly ignores 'commented out' args"""
+    _ip.alias_manager.define_alias('commetarg', 'echo this is %%s a "commented out" arg')
+    
+    with capture_output as cap:
+        _ip.run_cell('commetarg')
+    
+    nt.assert_equal(cap.stdout, 'this is %s a "commented out" arg')
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