Shift the responsibility of checking profile's size to the browser.

src/mono/wasm/Wasm.Build.Tests/TestAppScenarios/MemoryTests.cs

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
+using System.Text.RegularExpressions;
 using Xunit.Abstractions;
 using Xunit;
 
@@ -47,7 +48,15 @@ public async Task RunSimpleAppWithProfiler()
         BuildProject(config, assertAppBundle: false, extraArgs: extraArgs);
 
         var result = await RunSdkStyleAppForBuild(new (Configuration: config, TestScenario: "ProfilerTest"));
-        Console.WriteLine($"Test output: {result}");
-        // ToDo: check if the file is created AND its size it bigger than 10MB - where do we look for it?
+        Regex regex = new Regex(@"Profile data of size (\d+) bytes");
+        var match = result.TestOutput
+            .Select(line => regex.Match(line))
+            .FirstOrDefault(m => m.Success);
+        Assert.True(match != null, $"TestOuptup did not contain log matching {regex}");
+        if (!int.TryParse(match.Groups[1].Value, out int fileSize))
+        {
+            Assert.Fail($"Failed to parse profile size from {match.Groups[1].Value} to int");
+        }
+        Assert.True(fileSize >= 10 * 1024, $"Profile file size is less than 10KB. Actual size: {fileSize} bytes.");
     }
 }

src/mono/wasm/testassets/WasmBasicTestApp/App/wwwroot/profiler.js

@@ -1,28 +1,35 @@
 export function saveProfile(Module) {
-    let profileData = readProfileFile(Module);
+    const fileName = "output.mlpd";
+    let profileData = readProfileFile(Module, fileName);
+
+    if (!profileData) {
+        console.error("Profile data is empty or could not be read.");
+        return;
+    }
 
     const a = document.createElement('a');
     const blob = new Blob([profileData]);
     a.href = URL.createObjectURL(blob);
-    a.download = "output.mlpd";
+    a.download = fileName;
     // Append anchor to body.
     document.body.appendChild(a);
     a.click();
 
+    console.log(`TestOutput -> Profile data of size ${profileData.length} bytes started downloading.`);
+
     // Remove anchor from body
     document.body.removeChild(a);
 }
 
-function readProfileFile(Module) {
-    let profileFilePath="output.mlpd";
+function readProfileFile(Module, fileName) {
 
-    var stat = Module.FS.stat(profileFilePath);
+    var stat = Module.FS.stat(fileName);
 
     if (stat && stat.size > 0) {
-        return Module.FS.readFile(profileFilePath);
+        return Module.FS.readFile(fileName);
     }
     else {
-        console.debug(`Unable to fetch the profile file ${profileFilePath} as it is empty`);
+        console.debug(`Unable to fetch the profile file ${fileName} as it is empty`);
         return null;
     }
 }