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test: polish invariants #237
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@andreivladbrg I've been trying to figure out an invariant that compares the total debt with the streamed amount. It goes like the following: For any non-voided stream, the total debt should be equal to the total streamed amount minus the total withdrawn amount. I chose non-voided stream because |
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left some comments for now:
// Update the streamed amounts by adding up the difference between the ongoing debt before and after. | ||
for (uint256 i = 0; i < flowStore.lastStreamId(); ++i) { | ||
uint256 streamId = flowStore.streamIds(i); | ||
flowStore.updateStreamedAmount(streamId, flow.ongoingDebtOf(streamId) - initialOngoingDebts[i]); |
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This updates an incorrect streamed amount. Because it calls ongoingDebt
and add it to streamedAmount
very frequently, given that on every update, there will be some precision loss, then after a long time, when we compare the actual ongoing debt with the streamed amount, the different would be huge.
The actual ongoing debt = streamed amount + all those small amounts we missed in every update.
An alternate way is to store corrected time here and then use rps * (corrected time - previous stored time)
to calculate streamed amount in the invariant.
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I've removed it from this PR.
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test: invariant to compare total debt, streamed amount and withdrawn amount test: calculate streamed amount from ongoing debt before and after Co-authored-by: Andrei Vlad Birgaoanu <[email protected]> test(invariant): update function calls made by stream ID test(invariant): move depositAmount to CreateParams struct to avoid stack too deep error Co-authored-by: Andrei Vlad Birgaoanu <[email protected]> test: remove incorrect invariant
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Merging this as well since the changes in this PR are minor and will be useful during testing. |
Changelog
Depends on
vm.assume
in handlers #245Note
The following implementation is incorrect. See #237 (comment) for more details.
Until now, there was no way to validate the accuracy of the streamed amount. The amount streamed is only changed whenever there is a passage of time. Therefore, the new variablestreamedAmount
in FlowStore tracks the streamed amount throughadjustTimestamp
modifier.The precision-related problems that we had been facing are mostly introduced only in the_withdraw
function. So, the new invariant aims to validate that the update in the total debt matches the difference between the streamed amount and the withdrawn amount all the time.