Tests: Adds request URI diagnostics to InitTaskThreadSafe

Captures the absolute URI of every non-metadata HTTP request observed by the mock handler and surfaces the list in the assertion message when httpCallCount is unexpected.

Addresses Fabian's review feedback: lets us distinguish an AsyncCache race (duplicate I/O for the same URI) from two different HTTP requests legitimately issued by the client (e.g. an extra collection cache resolve). The previous assertion only exposed a count, making it hard to diagnose.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: NaluTripician

Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/ClientTests.cs

@@ -84,6 +84,7 @@ public async Task InitTaskThreadSafe()
         {
             int httpCallCount = 0;
             int metadataCallCount = 0;
+            ConcurrentBag<string> httpRequestUris = new ConcurrentBag<string>();
             bool delayCallBack = true;
 
             var isInitializedField = typeof(VmMetadataApiHandler).GetField("isInitialized",
@@ -100,15 +101,17 @@ public async Task InitTaskThreadSafe()
             {
                 RequestCallBack = async (request, cancellToken) =>
                 {
-                    if(request.RequestUri.AbsoluteUri ==  VmMetadataApiHandler.vmMetadataEndpointUrl.AbsoluteUri)
+                    string requestUri = request.RequestUri?.AbsoluteUri;
+                    if (requestUri == VmMetadataApiHandler.vmMetadataEndpointUrl.AbsoluteUri)
                     {
                         Interlocked.Increment(ref metadataCallCount);
-                    } 
+                    }
                     else
                     {
                         Interlocked.Increment(ref httpCallCount);
+                        httpRequestUris.Add(requestUri ?? "<null>");
                     }
-                    
+
                     while (delayCallBack)
                     {
                         await Task.Delay(TimeSpan.FromMilliseconds(100));
@@ -149,13 +152,19 @@ public async Task InitTaskThreadSafe()
                 await Task.WhenAll(tasks);
 
                 Assert.AreEqual(1, metadataCallCount, "Only one call for VM Metadata call with be made");
-                Assert.AreEqual(1, httpCallCount, "Only the first task should do the http call. All other should wait on the first task");
+                Assert.AreEqual(
+                    1,
+                    httpCallCount,
+                    $"Only the first task should do the http call. All other should wait on the first task. Observed URIs: [{string.Join(", ", httpRequestUris)}]");
 
                 // Reset counters and retry the client to verify a new http call is done for new requests
                 tasks.Clear();
                 delayCallBack = true;
                 this.TaskStartedCount = 0;
                 httpCallCount = 0;
+                while (httpRequestUris.TryTake(out _))
+                {
+                }
             }
         }