test: avoid panic if node is not properly encoded

[gabriele-0201]

It could happen that a leaf or branch node is not properly encoded,
causing the first key to be larger than the last one.
This could have led to a panic during the validation of the output.

[gabriele-0201]

• test: avoid panic if node is not properly encoded #573 👈 (View in Graphite)
• test: print branch/leaf_stage seed on stderr #570
• refactor: follow-up to leaf updater uses binary search #565 : 1 other dependent PR (#566 )
• fix: update BaseLeaf when keep_up_to jumps to end #564
• master

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[rphmeier]

The PR description isn't clear to me.

Why would we not want to panic if the btree node is not properly encoded? That sounds like a bug, and something we'd want tests to catch, no?

Can you add some context on the motivation?

[gabriele-0201]

Totally, that is a bug. This pr is not removing this check, but just making it explicit within the validation of the output, instead of possibly leaving expected_values.range(first..=last) to panic because last < first.

If an error like this currently occurs the output is something like

running 1 test
thread 'beatree::ops::update::tests::leaf_stage' panicked at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/alloc/src/collections/btree/search.rs:120:21:
range start is greater than range end in BTreeMap
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'beatree::ops::update::tests::leaf_stage' panicked at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/alloc/src/collections/btree/search.rs:120:21:
range start is greater than range end in BTreeMap
thread 'beatree::ops::update::tests::leaf_stage' panicked at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/alloc/src/collections/btree/search.rs:120:21:
range start is greater than range end in BTreeMap
...

while the check added in this pr becomes an explicit property required for the nodes, and the test output not passing becomes:

running 1 test
thread 'beatree::ops::update::tests::leaf_stage' panicked at /home/gabriele/.cargo/registry/src/index.crates.io-6f17d22bba15001f/quickcheck-1.0.3/src/tester.rs:165:28:
[quickcheck] TEST FAILED. Arguments: ({}, [0])
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
lead_stage failed with seed: [168, 16, 49, 83, 106, 24, 11, 24, 0, 0, 0, 0, 0, 0, 0, 0]
test beatree::ops::update::tests::leaf_stage ... FAILED