How can I avoid running some tests in parallel?

Question

I have a collection of tests. There are a few tests that need to access a shared resource (external library/API/hardware device). If any of these tests run in parallel, they

Answer 1

You can always provide your own test harness. You can do that by adding a [[test]] entry to Cargo.toml:

[[test]]
name = "my_test"
# If your test file is not `tests/my_test.rs`, add this key:
#path = "path/to/my_test.rs" 
harness = false

In that case, cargo test will compile my_test.rs as a normal executable file. That means you have to provide a main function and add all the "run tests" logic yourself. Yes, this is some work, but at least you can decide everything about running tests yourself.

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You can also create two test files:

tests/
  - sequential.rs
  - parallel.rs

You then would need to run cargo test --test sequential -- --test-threads=1 and cargo test --test parallel. So it doesn't work with a single cargo test, but you don't need to write your own test harness logic.