arg_matching_with_a_block.rb

# you can pass an implementation block, and use expectations in the block:
expect(MyClass).to receive(:method) do |arg_1, arg_2|
  expect(arg_1).to eq(2)
  expect(arg_2).to eq(3)
end

# or you can wrap any block in the `satisfy` (also aliased to `an_object_satisfying`) to turn it into a matcher:

expect(MyClass).to receive(:method).with(an_object_satisfying { |arg| arg.even? })