Guard browser OPFS machine file readback helper

wasm-port/tests/browser/interp_smoke.html

@@ -4539,6 +4539,11 @@
       verifyExpectedOutput(label, await loadTextFile(opfsPath), expectedText);
     }
 
+    async function verifyOpfsMachineFileReadback(label, machineId, fileKey, expectedText) {
+      const machineFiles = await loadMachineTextFiles(machineId);
+      verifyExpectedOutput(label, machineFiles[fileKey], expectedText);
+    }
+
     async function writeOpfsMachineFile(machineId, filename, text) {
       const opfsPath = opfsMachineFilePath(machineId, filename);
       await saveTextFile(opfsPath, text);
@@ -9237,10 +9242,10 @@
           "parameter_5399=66.6",
         ].join("\n"),
       );
-      const machineFiles = await loadMachineTextFiles(browserInterpMachineId);
-      verifyExpectedOutput(
+      await verifyOpfsMachineFileReadback(
         "opfs_saved_parameter_text",
-        machineFiles.parameters,
+        browserInterpMachineId,
+        "parameters",
         [
           "5161\t12.340000",
           "5162\t56.780000",
@@ -9281,10 +9286,10 @@
           "tool_1.pocketno=7",
         ].join("\n"),
       );
-      const savedMachineFiles = await loadMachineTextFiles(browserInterpMachineId);
-      verifyExpectedOutput(
+      await verifyOpfsMachineFileReadback(
         "opfs_saved_tool_table_text",
-        savedMachineFiles.toolTable,
+        browserInterpMachineId,
+        "toolTable",
         [
           "T2",
           "P7",
@@ -9391,12 +9396,10 @@
           "tool_pocket_9.toolno=5",
         ].join("\n"),
       );
-      const savedRandomMachineFiles = await loadMachineTextFiles(
-        browserRandomMachineId,
-      );
-      verifyExpectedOutput(
+      await verifyOpfsMachineFileReadback(
         "opfs_saved_random_tool_table_text",
-        savedRandomMachineFiles.toolTable,
+        browserRandomMachineId,
+        "toolTable",
         [
           "T2",
           "P7",