README.md

Basics

# create a double
obj = double()

# expect a message
obj.should_receive(:message)

# specify a return value
obj.should_receive(:message) { :value }
obj.should_receive(:message => :value)
obj.should_receive(:message).and_return(:value)

These forms are somewhat interchangeable. The difference is that the block contents are evaluated lazily when the obj receives the message message, whereas the others are evaluated as they are read.

Fake implementation

obj.should_receive(:message) do |arg1, arg2|
  # set expectations about the args in this block
  # and set a return value
end

Using the original implementation

obj.should_receive(:message).and_call_original

Raising/Throwing

obj.should_receive(:message).and_raise("this error")
obj.should_receive(:message).and_throw(:this_symbol)

You can also use the block format:

obj.should_receive(:message) { raise "this error" }
obj.should_receive(:message) { throw :this_symbol }

Argument constraints

Explicit arguments

obj.should_receive(:message).with('an argument')
obj.should_receive(:message).with('more_than', 'one_argument')

Argument matchers

obj.should_receive(:message).with(anything())
obj.should_receive(:message).with(an_instance_of(Money))
obj.should_receive(:message).with(hash_including(:a => 'b'))

Regular expressions

obj.should_receive(:message).with(/abc/)

Counts

obj.should_receive(:message).once
obj.should_receive(:message).twice
obj.should_receive(:message).exactly(3).times

obj.should_receive(:message).at_least(:once)
obj.should_receive(:message).at_least(:twice)
obj.should_receive(:message).at_least(n).times

obj.should_receive(:message).at_most(:once)
obj.should_receive(:message).at_most(:twice)
obj.should_receive(:message).at_most(n).times

Ordering

obj.should_receive(:one).ordered
obj.should_receive(:two).ordered