RSpec tips and tricks

rspec.rb

# Run specs with a given random seed
# rspec --seed <seed>

# Returning different values from consecutive stub invocations
allow(thing).to receive(:message).and_return(1, 2, 3, 4)

# Yielding multiple times from a test double
allow(thing).to receive(:each).and_yield(1).and_yield(2).and_yield(3).and_yield(4)

# Lightweight custom matcher
class Matcher
  def initialize(&match_proc)
    @match_proc = match_proc
  end
  
  def ==(value)
    @match_proc.call(value)
  end  
end

match = Matcher.new do |value|
  value == expected
end
allow(thing).to receive(:msg).with(match)