Check max possible keys in NVStore tests

[davidsaada]

Check max possible keys in NVStore tests: Boards that have large flash pages and small sectors may not be able to hold many NVStore keys. NVStore tests didn't take this into account and set a fixed number of keys. This PR checks the maximal number of keys before doing that, and if insufficient - the test is skipped.
Fixes #7649.

Pull request type

[x] Fix
[ ] Refactor
[ ] New target
[ ] Feature
[ ] Breaking change

[yossi2le]

Looks fine for me. Approved.

[0xc0170]

Looks fine, just a question that is not answered:

skipping this test does not have any coverage impact - all is fine?

[davidsaada]

skipping this test does not have any coverage impact - all is fine?

Good question. Skipping tests is a policy enforced in very extreme lack of resource cases. In our specific case, the test is skipped if the flash can't hold 20 NVStore keys, which is very extreme (and happened due to another bug, if you follow the issue). Now, we can dilute our tests to make them fit all low end boards, but then it would harm the test quality. We can also have a fixed list of boards, ones which we know that can handle the test (I know this is done in LittleFS tests). However, this will form a sort of a "white list", which covers less boards at the end of the day. So skipping tests in extreme cases seems like the right thing to do.

[0xc0170]

Thanks for the answer for testing also upper limit that not all boards can make. 👍

[cmonr]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2792
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7670/

Triggering tests

/morph test
/morph uvisor-test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2422
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7670/

[cmonr]

/morph test

[mbed-ci]

Test : FAILURE

Build number : 2527
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7670/2527

[cmonr]

Wat. There are no test results...

/morph test

[mbed-ci]

Test : FAILURE

Build number : 2537
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7670/2537

[davidsaada]

Yet another DNS test error. Everything else looks fine.

[adbridge]

Looks like this has failed due to some networking issues in CI. Suggest we re-run this once the CI is less heavily loaded.

[cmonr]

@davidsaada This particular test is also being moved out of the regular CI since it's causing so many false issues.

[cmonr]

/morph test

[mbed-ci]

Test : SUCCESS

Build number : 2553
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7670/2553