I am glad to present simplest mocks for Pharo.
mock := Mock new.
mock stub someMessage willReturn: 1000.
mock someMessage should be: 1000.
mock should got someMessage.
mock should not got anotherMessage.
rect := 0@0 corner: 2@3.
rect stub width willReturn: 1000.
rect area should be: 3000 "area = width * height".
rect should got width.