Testing

Three layers

Layer	What	Where	Command
Unit	Pure logic (path canonicalizer, `FixedPath`, `compare_paths`)	`#[cfg(test)]` in `src/`	`cargo test`
Smoke	Binary boots, binds, fakes root	CI `smoke test` step	`proot -0 id -u`, `proot -b …`
Reference suite	The C implementation’s full integration suite run against the Rust binary	`proot/tests/` in the C checkout	`make -C tests`

The third layer is the real contract — BoxKernel exists to be a drop-in replacement, so the C suite is the specification.

Running the reference suite

You need a checkout of the C reference next to this repo:

$ git clone https://github.com/termux/proot.git ../proot
$ cargo build --release
$ cd ../proot/tests
$ make test PROOT=/abs/path/to/BoxKernel/target/release/proot

Expected result (x86-64 host):

113 tests ok, 0 failed
8 skipped — tests requiring QEMU/rootfs artifacts not present
9 xfail/xpass — upstream-expected anomalies, identical to C

A change is done only when this suite is green — the same suite the C implementation passes.

Unit tests

In-file #[cfg(test)] modules cover the pieces with real specifications of their own:

fpath.rs — FixedPath NUL semantics, push/pop/chop, substitute_prefix branches
path/canon.rs — compare_paths (binding-prefix matching rules)

Add tests next to the code; keep them safe and fast. cargo test runs in CI on every push/PR.

Debugging a failing suite test

Each test is a shell or C program asserting a guest-visible behavior. Workflow:

$ cd ../proot/tests
$ ./test-0228fbe7.sh              # see the failure directly
$ PROOT=/path/to/proot ./test-0228fbe7.sh
$ PROOT_VERBOSE=9 …               # syscall-level trace if needed

Then bisect the pipeline: tracee/event stop → syscall/enter translation → path/canon → write-back → syscall/exit post- processing. The C source is the oracle for what each stage should produce.

Performance sanity

No formal benchmark yet. Quick sanity:

$ time proot -r rootfs /bin/sh -c 'for i in $(seq 1000); do /bin/true; done'
$ time proot -r rootfs /bin/sh -c 'cat large_file >/dev/null'

I/O-bound work should be near-native; syscall storms show the ptrace cost (seccomp helps where enabled).