arena tests might fail on mac OS due to unsafe memory handling

[Fullstop000]

Get result from cargo test:

test db::filename::tests::test_generate_filename ... ok
test db::format::tests::test_pack_seq_and_type ... ok
test db::filename::tests::test_parse_filename ... ok
test db::format::tests::test_internal_key_encode_decode ... ok
wickdb-4ab306f68f44e64d(32405,0x700008904000) malloc: *** error for object 0x11147a038: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
test mem::arena::tests::test_alloc_nodes ... ok
error: process didn't exit successfully: `/Users/fullstop000/rust/wickdb/target/debug/deps/wickdb-4ab306f68f44e64d` (signal: 6, SIGABRT: process abort signal)

But it is confused that all the tests are green if you use cargo test <mod name> for every mod.

And this only happens in mac OS.