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RSpec.shared_examples "an observer set" do
let (:observer_set) { described_class.new }
let (:observer) { double('observer') }
let (:another_observer) { double('another observer') }
describe '#add_observer' do
context 'with arguments' do
it 'should return the observer' do
expect(observer_set.add_observer(observer, :a_method)).to eq(observer)
end
end
context 'with a block' do
it 'should return the observer based on a block' do
observer = observer_set.add_observer { :block }
expect(observer.call).to eq(:block)
end
end
end
describe '#notify_observers' do
it 'should return the observer set' do
expect(observer_set.notify_observers).to be(observer_set)
end
context 'with a single observer' do
it 'should update a registered observer without arguments' do
expect(observer).to receive(:update).with(no_args)
observer_set.add_observer(observer)
observer_set.notify_observers
end
it 'should update a registered observer with arguments' do
expect(observer).to receive(:update).with(1, 2, 3)
observer_set.add_observer(observer)
observer_set.notify_observers(1, 2, 3)
end
it 'should notify an observer using the chosen method' do
expect(observer).to receive(:another_method).with('a string arg')
observer_set.add_observer(observer, :another_method)
observer_set.notify_observers('a string arg')
end
it 'should notify an observer once using the last added method' do
expect(observer).to receive(:another_method).with(any_args).never
expect(observer).to receive(:yet_another_method).with('a string arg')
observer_set.add_observer(observer, :another_method)
observer_set.add_observer(observer, :yet_another_method)
observer_set.notify_observers('a string arg')
end
it 'should notify an observer from a block' do
notification = double
expect(notification).to receive(:catch)
observer_set.add_observer {|arg| arg.catch }
observer_set.notify_observers notification
end
it 'can be called many times' do
expect(observer).to receive(:update).with(:an_arg).twice
expect(observer).to receive(:update).with(no_args).once
observer_set.add_observer(observer)
observer_set.notify_observers(:an_arg)
observer_set.notify_observers
observer_set.notify_observers(:an_arg)
end
end
context 'with many observers' do
it 'should notify all observer using the chosen method' do
expect(observer).to receive(:a_method).with(4, 'a')
expect(another_observer).to receive(:update).with(4, 'a')
observer_set.add_observer(observer, :a_method)
observer_set.add_observer(another_observer)
observer_set.notify_observers(4, 'a')
end
end
context 'with a block' do
before(:each) do
allow(observer).to receive(:update).with(any_args)
allow(another_observer).to receive(:update).with(any_args)
end
it 'calls the block once for every observer' do
counter = double('block call counter')
expect(counter).to receive(:called).with(no_args).exactly(2).times
observer_set.add_observer(observer)
observer_set.add_observer(another_observer)
observer_set.notify_observers{ counter.called }
end
it 'passes the block return value to the update method' do
expect(observer).to receive(:update).with(1, 2, 3, 4)
observer_set.add_observer(observer)
observer_set.notify_observers{ [1, 2, 3, 4] }
end
it 'accepts blocks returning a single value' do
expect(observer).to receive(:update).with(:foo)
observer_set.add_observer(observer)
observer_set.notify_observers{ :foo }
end
it 'accepts block return values that include arrays' do
expect(observer).to receive(:update).with(1, [2, 3], 4)
observer_set.add_observer(observer)
observer_set.notify_observers{ [1, [2, 3], 4] }
end
it 'raises an exception if given both arguments and a block' do
observer_set.add_observer(observer)
expect {
observer_set.notify_observers(1, 2, 3, 4){ nil }
}.to raise_error(ArgumentError)
end
end
end
context '#count_observers' do
it 'should be zero after initialization' do
expect(observer_set.count_observers).to eq 0
end
it 'should be 1 after the first observer is added' do
observer_set.add_observer(observer)
expect(observer_set.count_observers).to eq 1
end
it 'should be 1 if the same observer is added many times' do
observer_set.add_observer(observer)
observer_set.add_observer(observer, :another_method)
observer_set.add_observer(observer, :yet_another_method)
expect(observer_set.count_observers).to eq 1
end
it 'should be equal to the number of unique observers' do
observer_set.add_observer(observer)
observer_set.add_observer(another_observer)
observer_set.add_observer(double('observer 3'))
observer_set.add_observer(double('observer 4'))
expect(observer_set.count_observers).to eq 4
end
end
describe '#delete_observer' do
it 'should not notify a deleted observer' do
expect(observer).to receive(:update).never
observer_set.add_observer(observer)
observer_set.delete_observer(observer)
observer_set.notify_observers
end
it 'can delete a non added observer' do
observer_set.delete_observer(observer)
end
it 'should return the observer' do
expect(observer_set.delete_observer(observer)).to be(observer)
end
end
describe '#delete_observers' do
it 'should remove all observers' do
expect(observer).to receive(:update).never
expect(another_observer).to receive(:update).never
observer_set.add_observer(observer)
observer_set.add_observer(another_observer)
observer_set.delete_observers
observer_set.notify_observers
end
it 'should return the observer set' do
expect(observer_set.delete_observers).to be(observer_set)
end
end
describe '#notify_and_delete_observers' do
before(:each) do
observer_set.add_observer(observer, :a_method)
observer_set.add_observer(another_observer)
expect(observer).to receive(:a_method).with('args').once
expect(another_observer).to receive(:update).with('args').once
end
it 'should notify all observers' do
observer_set.notify_and_delete_observers('args')
end
it 'should clear observers' do
observer_set.notify_and_delete_observers('args')
expect(observer_set.count_observers).to eq(0)
end
it 'can be called many times without any other notification' do
observer_set.notify_and_delete_observers('args')
observer_set.notify_and_delete_observers('args')
observer_set.notify_and_delete_observers('args')
end
it 'should return the observer set' do
expect(observer_set.notify_and_delete_observers('args')).to be(observer_set)
end
end
end
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