Evict Metro bundle graphs after each Fantom test to prevent OOM

private/react-native-fantom/runner/bundling.js

@@ -28,6 +28,8 @@ export async function createBundle(options: BundleOptions): Promise<void> {
   let lastBundleResult;
   let lastBundleError;
 
+  const bundleURL = getBundleURL(options);
+
   // Retry in case Metro hasn't seen the changes in the filesystem yet.
   // TODO(T231910841): Remove this when Metro fixes consistency issues when resolving HTTP requests.
   let attemps = 0;
@@ -40,7 +42,7 @@ export async function createBundle(options: BundleOptions): Promise<void> {
     lastBundleResult = null;
 
     try {
-      lastBundleResult = await fetch(getBundleURL(options));
+      lastBundleResult = await fetch(bundleURL);
     } catch (e) {
       lastBundleError = e;
     }
@@ -72,6 +74,15 @@ export async function createBundle(options: BundleOptions): Promise<void> {
     await lastBundleResult.text(),
     'utf8',
   );
+
+  // Each test uses a unique entrypoint, so the bundle graph will never be
+  // requested again. Send DELETE to evict Metro's cached dependency graph
+  // and delta calculator for this bundle, freeing the memory.
+  try {
+    await fetch(bundleURL, {method: 'DELETE'});
+  } catch {
+    // Best-effort cleanup — don't fail the test if eviction fails.
+  }
 }
 
 export async function createSourceMap(options: BundleOptions): Promise<void> {

private/react-native-fantom/runner/global-setup/globalTeardown.js

@@ -14,6 +14,8 @@ type MetroServer = NonNullable<RunServerResult?.['httpServer']>;
 
 declare var __FANTOM_METRO_SERVER__: ?RunServerResult;
 
+const SHUTDOWN_TIMEOUT_MS = 5_000;
+
 function getMetroServer(): ?MetroServer {
   return typeof __FANTOM_METRO_SERVER__ !== 'undefined' &&
     __FANTOM_METRO_SERVER__ != null
@@ -32,7 +34,11 @@ export default async function globalTeardown(
 }
 
 async function stopMetroServer(metroServer: MetroServer): Promise<void> {
-  return new Promise((resolve, reject) => {
+  if (!metroServer.listening) {
+    return;
+  }
+
+  const closed = new Promise<void>((resolve, reject) => {
     metroServer.close(error => {
       if (error) {
         reject(error);
@@ -41,4 +47,21 @@ async function stopMetroServer(metroServer: MetroServer): Promise<void> {
       }
     });
   });
+
+  // $FlowFixMe[method-unbinding] Node 18.2+ API
+  if (typeof metroServer.closeIdleConnections === 'function') {
+    metroServer.closeIdleConnections();
+  }
+
+  const timeout = new Promise<void>(resolve => {
+    setTimeout(() => {
+      // $FlowFixMe[method-unbinding] Node 18.2+ API
+      if (typeof metroServer.closeAllConnections === 'function') {
+        metroServer.closeAllConnections();
+      }
+      resolve();
+    }, SHUTDOWN_TIMEOUT_MS);
+  });
+
+  await Promise.race([closed, timeout]);
 }