Fixing download 304 tests again. (Azure#33425)

* Fix for Download 304 live tests

* Removing mistake test

sdk/storage/Azure.Storage.Blobs/tests/BlobBaseClientTests.cs

@@ -1553,14 +1553,14 @@ public async Task DownloadTo_Initial304()
                 uploadResponse = await blob.UploadAsync(stream);
             }
 
-            CheckModifiedSinceAndWait(uploadResponse);
+            DateTimeOffset modifiedSince = CheckModifiedSinceAndWait(uploadResponse);
 
             // Add conditions to cause a failure and ensure we don't explode
             Response result = await blob.DownloadToAsync(
                 Stream.Null,
                 new BlobRequestConditions
                 {
-                    IfModifiedSince = Recording.UtcNow
+                    IfModifiedSince = modifiedSince
                 });
             Assert.AreEqual(304, result.Status);
         }
@@ -1580,14 +1580,14 @@ public async Task DownloadContent_Initial304()
                 uploadResponse = await blob.UploadAsync(stream);
             }
 
-            CheckModifiedSinceAndWait(uploadResponse);
+            DateTimeOffset modifiedSince = CheckModifiedSinceAndWait(uploadResponse);
 
             // Add conditions to cause a failure and ensure we don't explode
             Response<BlobDownloadResult> result = await blob.DownloadContentAsync(new BlobDownloadOptions
             {
                 Conditions = new BlobRequestConditions
                 {
-                    IfModifiedSince = Recording.UtcNow
+                    IfModifiedSince = modifiedSince
                 }
             });
             Assert.AreEqual(304, result.GetRawResponse().Status);
@@ -1608,14 +1608,14 @@ public async Task DownloadStreaming_Initial304()
                 uploadResponse = await blob.UploadAsync(stream);
             }
 
-            CheckModifiedSinceAndWait(uploadResponse);
+            DateTimeOffset modifiedSince = CheckModifiedSinceAndWait(uploadResponse);
 
             // Add conditions to cause a failure and ensure we don't explode
             Response<BlobDownloadStreamingResult> result = await blob.DownloadStreamingAsync(new BlobDownloadOptions
             {
                 Conditions = new BlobRequestConditions
                 {
-                    IfModifiedSince = Recording.UtcNow
+                    IfModifiedSince = modifiedSince
                 }
             });
             Assert.AreEqual(304, result.GetRawResponse().Status);
@@ -1636,13 +1636,13 @@ public async Task Download_Initial304()
                 uploadResponse = await blob.UploadAsync(stream);
             }
 
-            CheckModifiedSinceAndWait(uploadResponse);
+            DateTimeOffset modifiedSince = CheckModifiedSinceAndWait(uploadResponse);
 
             // Add conditions to cause a failure and ensure we don't explode
             Response<BlobDownloadInfo> result = await blob.DownloadAsync(
                 conditions: new BlobRequestConditions
                 {
-                    IfModifiedSince = Recording.UtcNow
+                    IfModifiedSince = modifiedSince
                 });
             Assert.AreEqual(304, result.GetRawResponse().Status);
         }

sdk/storage/Azure.Storage.Blobs/tests/BlobTestBase.cs

@@ -586,13 +586,17 @@ public void Handle(BlobQueryError blobQueryError)
         ///
         /// At most it's a 1 second difference wait. But most of the time there's no wait.
         /// </summary>
-        public void CheckModifiedSinceAndWait(Response<BlobContentInfo> uploadResponse)
+        /// <returns>Returns the time the IfModifiedSince should be for the Download Request to cause a 304</returns>
+        public DateTimeOffset CheckModifiedSinceAndWait(Response<BlobContentInfo> uploadResponse)
         {
             DateTimeOffset offsetNow = Recording.UtcNow;
             if (DateTimeOffset.Compare(uploadResponse.Value.LastModified, offsetNow) > 0)
             {
+                // Wait the difference plus 2 second
                 Thread.Sleep(uploadResponse.Value.LastModified.Subtract(offsetNow));
+                offsetNow = uploadResponse.Value.LastModified;
             }
+            return offsetNow;
         }
     }
 }