Backtraces

As mentioned in the output, we can set the environment variable RUST_BACKTRACE to 1 in order to get more information about where the test failed. Let's do so:

export RUST_BACKTRACE=1

    Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs
     Running target/debug/deps/ftp_server-452667ddc2d724e8

running 2 tests
test codec::tests::test_encoder ... ok
test codec::tests::test_dummy ... FAILED

failures:

---- codec::tests::test_dummy stdout ----
    thread 'codec::tests::test_dummy' panicked at 'Always fail', src/codec.rs:102:8
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /checkout/src/libstd/sys_common/backtrace.rs:68
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/sys_common/backtrace.rs:57
             at /checkout/src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:391
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:577
   5: std::panicking::begin_panic
             at /checkout/src/libstd/panicking.rs:538
   6: ftp_server::codec::tests::test_dummy
             at src/codec.rs:102
   7: <F as test::FnBox<T>>::call_box
             at /checkout/src/libtest/lib.rs:1491
             at /checkout/src/libcore/ops/function.rs:223
             at /checkout/src/libtest/lib.rs:142
   8: __rust_maybe_catch_panic
             at /checkout/src/libpanic_unwind/lib.rs:99


failures:
    codec::tests::test_dummy

test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out

error: test failed, to rerun pass '--bin ftp-server'

The important part here is the following:

6: ftp_server::codec::tests::test_dummy
             at src/codec.rs:102

This shows the file, function, and line where the code panicked.

This variable is useful even outside of testing code: when debugging a problem with a code that panics, we can use this variable as well.