def test_empty_expression():
from stilus.nodes.null import null
from stilus.nodes.boolean import false
expression = Expression()
assert len(expression) == 0
assert expression.is_empty()
assert expression.first() is null
assert expression.to_boolean() is false
def test_expression_string_first_boolean():
from stilus.nodes.boolean import true
from stilus.nodes.boolean import false
from stilus.nodes.null import null
expression = Expression()
expression.append(true)
expression.append(false)
expression.append(null)
assert str(expression) == "(true false null)"
expression.is_list = True
assert str(expression) == "(true, false, null)"
assert expression.first() is true
assert expression.to_boolean().value is True