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require 'spec_helper'
require 'concurrent/atomics'
describe Immutable::List do
it 'ensures each node of a lazy list will only be realized on ONE thread, even when accessed by multiple threads' do
counter = Concurrent::Atom.new(0)
list = (1..10000).to_list.map { |x| counter.swap { |count| count + 1 }; x * 2 }
threads = 10.times.collect do
Thread.new do
node = list
node = node.tail until node.empty?
end
end
threads.each(&:join)
counter.value.should == 10000
list.sum.should == 100010000
end
it "doesn't go into an infinite loop if lazy list block raises an exception" do
list = (1..10).to_list.map { raise 'Oops!' }
threads = 10.times.collect do
Thread.new do
-> { list.head }.should raise_error(RuntimeError)
end
end
threads.each(&:join)
end
it "doesn't give horrendously bad performance if thread realizing the list sleeps" do
start = Time.now
list = (1..100).to_list.map { |x| sleep(0.001); x * 2 }
threads = 10.times.collect do
Thread.new do
node = list
node = node.tail until node.empty?
end
end
threads.each(&:join)
elapsed = Time.now - start
elapsed.should_not > 0.3
end
end
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