tamer: Ensure debug_assert! takes effect in test profile

I'd feel rather silly if I used `debug_assert!` for the sake of tests and
they weren't actually being run due to optimization settings.

This is just to catch potential future regressions; all is well today.

DEV-7145

tamer/src/test/mod.rs

@@ -18,3 +18,18 @@
 //  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 pub mod quick_xml;
+
+/// Ensures that tests will hit debug assertions.
+///
+/// Debug assertions are used to enforce invariants that would certainly be
+///   hit by tests if violated,
+///     and so have no need to be included in release builds.
+///
+/// If this test fails,
+///   then optimization settings are inhibiting debug assertions.
+/// See the documentation for [`debug_assert!`] for more information.
+#[test]
+#[should_panic]
+fn uses_debug_assertions() {
+    debug_assert!(false, "should panic");
+}