Spanner: "before all" hook for "should have created an instance" failed

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commit: ffb88bb
buildURL: Build Status, Sponge
status: failed

Test output

Cannot read property 'filter' of undefined
TypeError: Cannot read property 'filter' of undefined
    at /workspace/samples/system-test/spanner.test.js:111:12
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
    at async Promise.all (index 0)
    at async deleteStaleInstances (system-test/spanner.test.js:97:3)
    at async Context. (system-test/spanner.test.js:197:5)

[skuruppu]

This is what used to happen to me locally on #866 when I tried to run the samples tests. Now it seems to be happening on Kokoro as well.

[AVaksman]

It seems the current behavior has to do with an old instance that doesn't have any logs of the operations.
We couldn't find any documentation regarding how long do logs/operation stay and when they are removed.

The code responsible for such unstable behavior will be removed and a slightly different verification routine will be put in place.
We will rather use another label created instead. Similar logic is already in place in system-tests.

@laljikanjareeya will rase a PR soon.