IPython/core/tests/test_alias.py

from IPython.utils.capture import capture_output

import pytest

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)
    assert am.retrieve_alias(name) == cmd
    assert (name, cmd) in 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]
        assert result == [cmd]
    finally:
        _ip.system = orig_system
    
    # Test removing the alias
    am.undefine_alias(name)
    assert not am.is_alias(name)
    with pytest.raises(ValueError):
        am.retrieve_alias(name)
    assert (name, cmd) not in 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')

    assert cap.stderr.split(":")[0] == "UsageError"


def test_alias_args_commented():
    """Check that alias correctly ignores 'commented out' args"""
    _ip.run_line_magic("alias", "commentarg echo this is %%s a commented out arg")

    with capture_output() as cap:
        _ip.run_cell("commentarg")

    # strip() is for pytest compat; testing via iptest patch IPython shell
    # in testing.globalipapp and replace the system call which messed up the
    # \r\n
    assert cap.stdout.strip() ==  'this is %s a commented out arg'

def test_alias_args_commented_nargs():
    """Check that alias correctly counts args, excluding those commented out"""
    am = _ip.alias_manager
    alias_name = 'comargcount'
    cmd = 'echo this is %%s a commented out arg and this is not %s'
    
    am.define_alias(alias_name, cmd)
    assert am.is_alias(alias_name)
    
    thealias = am.get_alias(alias_name)
    assert thealias.nargs == 1