From df95d86c8e98392b97db0b7ac4ed615148ba795d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rub=C3=A9n=20Norte?= <rubennorte@meta.com>
Date: Tue, 14 Apr 2026 04:19:25 -0700
Subject: [PATCH 1/2] Skip reporting benchmark results in test mode

Summary:
Avoid printing the result summary table when benchmarks are executed in
test mode. In test mode, benchmarks run only a single iteration with no
warmup, so the timing results are not meaningful for comparison.

The per-suite results table (console.table) was already skipped in test
mode, but the benchmark result was still reported to the runner, which
could cause the cross-variant comparison table to be printed with
meaningless data. This change skips the reportBenchmarkResult call
entirely when running in test mode.

Changelog: [Internal]

Differential Revision: D100795458
---
 private/react-native-fantom/src/Benchmark.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/private/react-native-fantom/src/Benchmark.js b/private/react-native-fantom/src/Benchmark.js
index a4b8af047b79..f93912bc967e 100644
--- a/private/react-native-fantom/src/Benchmark.js
+++ b/private/react-native-fantom/src/Benchmark.js
@@ -215,7 +215,9 @@ export function suite(
         'Failing focused test to prevent it from being committed',
       );
     }
-    reportBenchmarkResult(createBenchmarkResultsObject(bench, tasks));
+    if (!isTestOnly) {
+      reportBenchmarkResult(createBenchmarkResultsObject(bench, tasks));
+    }
   });
 
   const test = (name: string, fn: SyncFn, options?: FnOptions): SuiteAPI => {

From aa03ec017a54f15b934086dc53b4bd0b74d8e2e6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rub=C3=A9n=20Norte?= <rubennorte@meta.com>
Date: Tue, 14 Apr 2026 04:19:25 -0700
Subject: [PATCH 2/2] Automatically set --runInBand when running benchmarks

Summary:
When `--benchmarks` is passed to `yarn fantom`, automatically append
`--runInBand` to the Jest arguments. This ensures benchmarks run
sequentially in the same process, avoiding parallel test execution that
would introduce noise in performance measurements.

Changelog: [Internal]

Differential Revision: D100796022
---
 scripts/fantom.sh | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/fantom.sh b/scripts/fantom.sh
index 0b34f9807d28..5d4be07aa77c 100755
--- a/scripts/fantom.sh
+++ b/scripts/fantom.sh
@@ -27,4 +27,8 @@ for arg in "$@"; do
   esac
 done
 
+if [[ -n "$FANTOM_RUN_BENCHMARKS" ]]; then
+  ARGS+=("--runInBand")
+fi
+
 yarn jest --config private/react-native-fantom/config/jest.config.js "${ARGS[@]}"