diff --git a/update-engine/src/buffer.rs b/update-engine/src/buffer.rs
index f3395e4667..1779ef7da6 100644
--- a/update-engine/src/buffer.rs
+++ b/update-engine/src/buffer.rs
@@ -1391,6 +1391,7 @@ mod tests {
                 "all events passed in",
                 |buffer, event| {
                     buffer.add_event(event.clone());
+                    true
                 },
                 WithDeltas::No,
             )
@@ -1402,8 +1403,9 @@ mod tests {
                 |buffer, event| match event {
                     Event::Step(event) => {
                         buffer.add_step_event(event.clone());
+                        true
                     }
-                    Event::Progress(_) => {}
+                    Event::Progress(_) => false,
                 },
                 WithDeltas::Both,
             )
@@ -1416,11 +1418,13 @@ mod tests {
                     Event::Step(event) => match event.kind.priority() {
                         StepEventPriority::High => {
                             buffer.add_step_event(event.clone());
+                            true
                         }
-                        StepEventPriority::Low => {}
+                        StepEventPriority::Low => false,
                     },
                     Event::Progress(event) => {
                         buffer.add_progress_event(event.clone());
+                        true
                     }
                 },
                 WithDeltas::Both,
@@ -1434,11 +1438,13 @@ mod tests {
                     Event::Step(event) => match event.kind.priority() {
                         StepEventPriority::High => {
                             buffer.add_step_event(event.clone());
+                            true
                         }
-                        StepEventPriority::Low => {}
+                        StepEventPriority::Low => false,
                     },
                     Event::Progress(_) => {
                         // Don't add progress events.
+                        false
                     }
                 },
                 WithDeltas::Both,
@@ -1570,7 +1576,10 @@ mod tests {
         fn run_filtered_test(
             &self,
             event_fn_description: &str,
-            mut event_fn: impl FnMut(&mut EventBuffer<TestSpec>, &Event<TestSpec>),
+            mut event_fn: impl FnMut(
+                &mut EventBuffer<TestSpec>,
+                &Event<TestSpec>,
+            ) -> bool,
             with_deltas: WithDeltas,
         ) -> anyhow::Result<()> {
             match with_deltas {
@@ -1595,7 +1604,10 @@ mod tests {
 
         fn run_filtered_test_inner(
             &self,
-            mut event_fn: impl FnMut(&mut EventBuffer<TestSpec>, &Event<TestSpec>),
+            mut event_fn: impl FnMut(
+                &mut EventBuffer<TestSpec>,
+                &Event<TestSpec>,
+            ) -> bool,
             with_deltas: bool,
         ) -> anyhow::Result<()> {
             let description = format!("with deltas = {with_deltas}");
@@ -1613,7 +1625,8 @@ mod tests {
             let mut last_seen_opt = with_deltas.then_some(None);
 
             for (i, event) in self.generated_events.iter().enumerate() {
-                (event_fn)(&mut buffer, event);
+                // Going to use event_added in an upcoming commit.
+                let _event_added = (event_fn)(&mut buffer, event);
 
                 let report = match last_seen_opt {
                     Some(last_seen) => buffer.generate_report_since(last_seen),