Background

[SC-67432]

Sometimes (2 in 1000 runs) this test fails with:

Expected completedTask.Count(x => x != *******) to be less than 400, but found 400.

This might be because:

cancelling the cancellation token on the tuple is relatively slow, while de-queueing from the queue is relatively fast.
the count of cancelled requests was incremented before the CancellationTokenSource was cancelled.
the number of completed tasks could legitimately be 400 if exactly 100 requests were cancelled. (total request count is 500)

this means it might be possible to be in a state in which only:

tasks are cancelled!

Thus 400 tasks (or technically even 401 tasks) could have completed successfully. Explaining the to be less than 400, but found 400. error.

The fix is to:

check that completed is smaller than or equal to total tasks - cancelled tasks.
the count of cancelled request to only be incremented if the request is actually cancelled.

Pre-requisites

[ ] I have read How we use GitHub Issues for help deciding when and where it's appropriate to make an issue.
[ ] I have considered informing or consulting the right people, according to the ownership map.
[ ] I have considered appropriate testing for my change.