def test_no_tokens_should_return_empty_root_node(self):
node = build_tree([])
assert isinstance(node, RootNode)
assert node.eval() is None
def test_nested_expression(self):
lexer = Lexer()
tokens = lexer.analyze('(+ 1 (+ 1 (+ 1 1)))')
node = build_tree(tokens)
assert 4 == node.eval()
def test_empty_expression(self):
lexer = Lexer()
tokens = lexer.analyze('()')
node = build_tree(tokens)
assert node.eval() is None
def test_simple_expression(self):
lexer = Lexer()
tokens = lexer.analyze('(+ 1 1)')
node = build_tree(tokens)
assert 2 == node.eval()
def eval(expr):
lexer = Lexer()
node = build_tree(lexer.analyze(expr))
return node.eval()