chore: Test COBS functions

[zfields]

No description provided.

[Copilot]

Pull request overview

Adds Catch2 unit coverage for COBS helper functions and adjusts COBS sizing helpers to better handle edge cases (notably zero-length inputs) and centralize constants.

Changes:

• Added new Catch2 test suites covering _cobsDecode, _cobsEncode, _cobsEncodedLength, _cobsEncodedMaxLength, and _cobsGuaranteedFit.
• Registered the new COBS tests in the test CMake target list.
• Updated n_cobs.c to introduce COBS_MAX_PACKET_SIZE and revise _cobsEncodedMaxLength / _cobsGuaranteedFit calculations.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
test/src/_cobsGuaranteedFit_test.cpp	Adds unit tests for _cobsGuaranteedFit across boundary conditions.
test/src/_cobsEncodedMaxLength_test.cpp	Adds unit tests for _cobsEncodedMaxLength, including length=0.
test/src/_cobsEncodedLength_test.cpp	Adds unit tests for _cobsEncodedLength correctness and input immutability.
test/src/_cobsEncode_test.cpp	Adds unit tests for _cobsEncode, including in-place encoding and non-zero EOP.
test/src/_cobsDecode_test.cpp	Adds unit tests for _cobsDecode, including in-place decoding and non-zero EOP.
test/CMakeLists.txt	Registers the new COBS unit test executables with CTest discovery.
n_cobs.c	Centralizes max packet size constant and updates worst-case sizing/fit computations.

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[zfields]

Unit-test error generated by Valgrind:

GIVEN A specified EOP byte of 0x00
AND_GIVEN An array capable of being COBS-encoded in-place
WHEN The array is COBS-encoded in-place

==32108== Memcheck, a memory error detector
==32108== Copyright (C) 2002-2024, and GNU GPL'd, by Julian Seward et al.
==32108== Using Valgrind-3.24.0 and LibVEX; rerun with -h for copyright info
==32108== Command: /workspaces/note-c/build/test/_cobsEncode_test Scenario:\ _cobsEncode
==32108== Parent PID: 32096
==32108== 
==32108== Source and destination overlap in memcpy(0xfef05a86, 0xfef05a86, 1)
==32108==    at 0x484DE20: memcpy (vg_replace_strmem.c:1150)
==32108==    by 0x486E863: _cobsEncode (n_cobs.c:149)
==32108==    by 0x112954: (anonymous namespace)::CATCH2_INTERNAL_TEST_0() (_cobsEncode_test.cpp:35)
==32108==    by 0x182D73: Catch::TestInvokerAsFunction::invoke() const (in /workspaces/note-c/build/test/_cobsEncode_test)
==32108==    by 0x1777E3: Catch::TestCaseHandle::invoke() const (in /workspaces/note-c/build/test/_cobsEncode_test)
==32108==    by 0x176BDB: Catch::RunContext::invokeActiveTestCase() (in /workspaces/note-c/build/test/_cobsEncode_test)
==32108==    by 0x17692F: Catch::RunContext::runCurrentTest(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&) (in /workspaces/note-c/build/test/_cobsEncode_test)
==32108==    by 0x1751D7: Catch::RunContext::runTest(Catch::TestCaseHandle const&) (in /workspaces/note-c/build/test/_cobsEncode_test)
==32108==    by 0x12BAFC: Catch::(anonymous namespace)::TestGroup::execute() (in /workspaces/note-c/build/test/_cobsEncode_test)
==32108==    by 0x12CEEB: Catch::Session::runInternal() (in /workspaces/note-c/build/test/_cobsEncode_test)
==32108==    by 0x12CA66: Catch::Session::run() (in /workspaces/note-c/build/test/_cobsEncode_test)
==32108==    by 0x129122: int Catch::Session::run<char>(int, char const* const*) (in /workspaces/note-c/build/test/_cobsEncode_test)
==32108== 
==32108== 
==32108== HEAP SUMMARY:
==32108==     in use at exit: 0 bytes in 0 blocks
==32108==   total heap usage: 4,786 allocs, 4,786 frees, 485,384 bytes allocated
==32108== 
==32108== All heap blocks were freed -- no leaks are possible
==32108== 
==32108== For lists of detected and suppressed errors, rerun with: -s
==32108== ERROR SUMMARY: 6 errors from 1 contexts (suppressed: 0 from 0)

UPDATE: memcpy -> memmove (resolved this issue)