def test_lexer_newlines():
assert list(lexer.lex('\n')) == [Token('NL', '\n')]
assert list(lexer.lex('\n\n\n')) == [Token('NL', '\n\n\n')]
def test_lexer_id():
assert list(lexer.lex('new_var')) == [Token('ID', 'new_var')]
def test_sub():
assert list(lexer.lex('-')) == [Token('SUB', '-')]
def test_add():
assert list(lexer.lex('+')) == [Token('ADD', '+')]
def test_assign():
assert list(lexer.lex('=')) == [Token('ASSIGN', '=')]
def test_nospace():
assert list(lexer.lex(' ')) == []
def test_int():
assert list(lexer.lex('1')) == [Token('INT', '1')]
