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module Concurrent
RSpec.describe TVar do
context '#initialize' do
it 'accepts an initial value' do
t = TVar.new(14)
expect(t.value).to eq 14
end
end
context '#value' do
it 'gets the value' do
t = TVar.new(14)
expect(t.value).to eq 14
end
end
context '#value=' do
it 'sets the value' do
t = TVar.new(14)
t.value = 2
expect(t.value).to eq 2
end
end
end
RSpec.describe '#atomically' do
it 'raises an exception when no block given' do
expect { Concurrent::atomically }.to raise_error(ArgumentError)
end
it 'raises the same exception that was raised in Concurrent::atomically' do
expect {
Concurrent::atomically do
raise StandardError, 'This is an error!'
end
}.to raise_error(StandardError, 'This is an error!')
end
it 'retries on abort' do
count = 0
Concurrent::atomically do
if count == 0
count = 1
Concurrent::abort_transaction
else
count = 2
end
end
expect(count).to eq 2
end
it 'commits writes if the transaction succeeds' do
t = TVar.new(0)
Concurrent::atomically do
t.value = 1
end
expect(t.value).to eq 1
end
it 'undoes writes if the transaction is aborted' do
t = TVar.new(0)
count = 0
Concurrent::atomically do
if count == 0
t.value = 1
count = 1
Concurrent::abort_transaction
end
end
expect(t.value).to eq 0
end
it 'provides atomicity' do
t1 = TVar.new(0)
t2 = TVar.new(0)
count = 0
Concurrent::atomically do
if count == 0
count = 1
t1.value = 1
Concurrent::abort_transaction
t2.value = 2
end
end
expect(t1.value).to eq 0
expect(t2.value).to eq 0
end
it 'provides weak isolation' do
t = TVar.new(0)
a = CountDownLatch.new
b = CountDownLatch.new
in_thread do
Concurrent::atomically do
t.value = 1
a.count_down
b.wait
Concurrent.leave_transaction
end
end
Concurrent::atomically do
a.wait
expect(t.value).to eq 0
b.count_down
Concurrent.leave_transaction
end
end
it 'is implemented with lazy writes' do
t = TVar.new(0)
a = CountDownLatch.new
b = CountDownLatch.new
in_thread do
Concurrent::atomically do
t.value = 1
a.count_down
b.wait
end
end
a.wait
expect(t.value).to eq 0
b.count_down
end
it 'nests' do
t = TVar.new(0)
Concurrent::atomically do
expect(t.value).to eq 0
t.value = 1
Concurrent::atomically do
expect(t.value).to eq 1
t.value = 2
Concurrent::atomically do
expect(t.value).to eq 2
t.value = 3
end
expect(t.value).to eq 3
t.value = 4
end
expect(t.value).to eq 4
t.value = 5
end
expect(t.value).to eq 5
end
it 'reflects transactional writes from within the same transaction' do
t = TVar.new(0)
Concurrent::atomically do
expect(t.value).to eq 0
t.value = 14
expect(t.value).to eq 14
t.value = 2
expect(t.value).to eq 2
end
end
end
RSpec.describe '#abort_transaction' do
it 'raises an exception outside an #atomically block' do
expect { Concurrent::abort_transaction }.to raise_error(Concurrent::Transaction::AbortError)
end
end
RSpec.describe '#leave_transaction' do
it 'raises an exception outside an #atomically block' do
expect { Concurrent::leave_transaction }.to raise_error(Concurrent::Transaction::LeaveError)
end
it 'neither commits nor aborts a transaction' do
t = TVar.new(0)
Concurrent::atomically do
expect(t.value).to eq 0
t.value = 14
Concurrent::leave_transaction
end
expect(t.value).to eq 0
end
end
end
|
