Add some unit tests (rustc copy)

[phansch]

Same as rust-lang/rust#56841

[laumann]

I take it we want this merged before #151?

[phansch]

It's independent of #151 so can be merged whenever =)

[phansch]

I added the unit test execution to CI but it looks like running the unit tests on stable causes:

error[E0308]: mismatched types
   --> src/util.rs:116:1
    |
116 | / fn test_get_arch_failure() {
117 | |     get_arch("abc");
118 | | }
    | |_^ expected struct `test::TestDescAndFn`, found reference
    |
    = note: expected type `test::TestDescAndFn`
               found type `&test::TestDescAndFn`

[phansch]

I'm not really sure how to fix it. I guess the tester crate needs an update?

[laumann]

@phansch Thanks for you contributions, and I'm sorry for acting so slow on them. It is not my intention! Oh, and happy New Year :-)

Hmm, the tester crate might need an update, @messense what do you think?

Otherwise, we could opt to omit the last commit in this PR, and add the testing later.

[messense]

Hmm, the tester crate might need an update.

Sure thing. The repository is here: https://github.com/messense/rustc-test if any of you guys want to update it.

[phansch]

Maybe not 100% related, but would it make sense to depend on https://github.com/rust-lang/libtest instead of the tester crate in the future?

[laumann]

Maybe not 100% related, but would it make sense to depend on https://github.com/rust-lang/libtest instead of the tester crate in the future?

Hmm, libtest seems to be targeted at nightly only, the tester crate is specifically to add stable support. I could be wrong though.

I tried a couple of times to dig into the error with the tester crate, but never got to the bottom of it (mostly due to lack of time).

[phansch]

I won't have time to dig into this either, so I'm going ahead and close this PR. If someone want's to pick it up, feel free to take it =)