test-renderers: Add timeout.

test-renderers/Cargo.toml

@@ -79,7 +79,7 @@ tempfile = { workspace = true }
 # so let's use it for our output report template.
 tinytemplate = "1.2.1"
 # Using tokio for async test-running.
-tokio = { workspace = true, features = ["macros", "rt", "rt-multi-thread", "parking_lot", "sync"] }
+tokio = { workspace = true, features = ["macros", "rt", "rt-multi-thread", "parking_lot", "sync", "time"] }
 wgpu = { workspace = true }
 
 [lints]

test-renderers/src/harness.rs

@@ -322,8 +322,16 @@ where
                         image_serial: 0,
                     };
 
+                    // Run the test case; its pass or fail (if it doesn't panic) is determined
+                    // by the comparison_log contents.
+                    // The timeout is in case the renderer hangs, so that we get a faster and more
+                    // specific answer than an entire CI job timeout. (Generally, renders should
+                    // finish in fractions of a second, but CI can be very slow; the large timeout
+                    // is to avoid flakiness under edge cases of high machine load.)
                     let case_start_time = Instant::now();
-                    (test_case.function)(context).await;
+                    tokio::time::timeout(Duration::from_secs(30), (test_case.function)(context))
+                        .await
+                        .expect("render test case timed out");
                     case_start_time.elapsed()
                 });
                 let outcome: Result<Duration, tokio::task::JoinError> = test_case_handle.await;