Add test for alias creation, use and destruction

IPython/core/tests/test_alias.py

@@ -0,0 +1,41 b''
+from IPython.utils.capture import capture_output
+
+import nose.tools as nt
+
+def test_alias_lifecycle():
+    name = 'test_alias1'
+    cmd = 'echo "Hello"'
+    am = _ip.alias_manager
+    am.clear_aliases()
+    am.define_alias(name, cmd)
+    assert am.is_alias(name)
+    nt.assert_equal(am.retrieve_alias(name), cmd)
+    nt.assert_in((name, cmd), am.aliases)
+    
+    # Test running the alias
+    orig_system = _ip.system
+    result = []
+    _ip.system = result.append
+    try:
+        _ip.run_cell('%{}'.format(name))
+        result = [c.strip() for c in result]
+        nt.assert_equal(result, [cmd])
+    finally:
+        _ip.system = orig_system
+    
+    # Test removing the alias
+    am.undefine_alias(name)
+    assert not am.is_alias(name)
+    with nt.assert_raises(ValueError):
+        am.retrieve_alias(name)
+    nt.assert_not_in((name, cmd), am.aliases)
+    
+
+def test_alias_args_error():
+    """Error expanding with wrong number of arguments"""
+    _ip.alias_manager.define_alias('parts', 'echo first %s second %s')
+    # capture stderr:
+    with capture_output() as cap:
+        _ip.run_cell('parts 1')
+
+    nt.assert_equal(cap.stderr.split(':')[0], 'UsageError')
  No newline at end of file

IPython/core/tests/test_interactiveshell.py

@@ -106,17 +106,6 b' class InteractiveShellTestCase(unittest.TestCase):'
         ip.run_cell('a = """\n%exit\n"""')
         self.assertEqual(ip.user_ns['a'], '\n%exit\n')
     
-    def test_alias_crash(self):
-        """Errors in prefilter can't crash IPython"""
-        ip.run_cell('%alias parts echo first %s second %s')
-        # capture stderr:
-        save_err = io.stderr
-        io.stderr = StringIO()
-        ip.run_cell('parts 1')
-        err = io.stderr.getvalue()
-        io.stderr = save_err
-        self.assertEqual(err.split(':')[0], 'ERROR')
-    
     def test_trailing_newline(self):
         """test that running !(command) does not raise a SyntaxError"""
         ip.run_cell('!(true)\n', False)