diff --git a/Note-testsuite.md b/Note-testsuite.md
index d843e38..2f7804e 100644
--- a/Note-testsuite.md
+++ b/Note-testsuite.md
@@ -153,13 +153,19 @@ run-pass/cci_iter_exe.rs:
 
 ## Unit Tests
 
-Most crates include <a href="https://github.com/mozilla/rust/wiki/Doc-unit-testing">unit tests</a> which are part of the crate they test. These crates are built with the --test flag and run as part of `make check`.
+Most crates include <a href="https://github.com/mozilla/rust/wiki/Doc-unit-testing">unit tests</a> which are part of the crate they test. These crates are built with the --test` flag and run as part of `make check`.
 
-Tests should go near the code they test. If a module's tests require additional helper functions then they should be enclosed in a conditionally-compiled test module:
+All tests in a module should go in an inner module named `test`, with the attribute `#[cfg(test)]`. Placing tests in their own module is a practical issue - because test cases are not included in normal builds, building with `--test` require a different set of imports than without, and that causes 'unused import' errors.
 
 ```
+use std::option;
+
+fn do_something() { ... }
+
 #[cfg(test)]
 mod test {
+   use std::vec;
+
    fn helper_fn() { ... }
 
    #[test]