Timestamp snapshot name to use seven digits precision for fraction of a second (#655)

* Increase fraction of a second to seven digits precision when creating a snapshot name from a time stamp

* Update tests to validate snapshot names created 1 microsecond apart

Author: Francisco-Gamino

src/DependencyManagement/DependencySnapshotFolderNameTools.cs

@@ -20,7 +20,7 @@ internal static class DependencySnapshotFolderNameTools
 
         public static string CreateUniqueName()
         {
-            var uniqueBase = DateTime.UtcNow.ToString("yyMMddHHmmssfff");
+            var uniqueBase = DateTime.UtcNow.ToString("yyMMddHHmmssfffffff");
             return uniqueBase + InstalledPostfix;
         }
 
@@ -29,9 +29,9 @@ public static string CreateUniqueName()
         /// appending a postfix, so that that the resulting path follows a different
         /// pattern and can be discovered using a different file mask.
         /// For example, for the _installed_ path
-        ///     ".../1907101234567.r"
+        ///     ".../2107131600546921703.r"
         /// the _installing_ path will be:
-        ///     ".../1907101234567.ri"
+        ///     ".../2107131600546921703.ri"
         /// This makes it possible to enumerate all the installed snapshots by using ".../*.r" mask,
         /// and all the installing snapshots by using ".../*i" mask.
         /// </summary>

test/Unit/DependencyManagement/DependencySnapshotFolderNameToolsTests.cs

@@ -10,14 +10,19 @@ namespace Microsoft.Azure.Functions.PowerShellWorker.Test.DependencyManagement
     using Xunit;
 
     using Microsoft.Azure.Functions.PowerShellWorker.DependencyManagement;
+    using System;
 
     public class DependencySnapshotFolderNameToolsTests
     {
         [Fact]
         public void CreatesUniqueEnoughNames()
         {
+            // ticks = microseconds * (TimeSpan.TicksPerMillisecond / 1000)
+            // A snapshot name created 1 microsecond (10 ticks) later must be different
+            var waitTime = new TimeSpan(10);
+
             var name1 = DependencySnapshotFolderNameTools.CreateUniqueName();
-            Thread.Sleep(2); // A snapshot name created 2 milliseconds later must be different
+            Thread.Sleep(waitTime);
             var name2 = DependencySnapshotFolderNameTools.CreateUniqueName();
             Assert.NotEqual(name1, name2);
         }
@@ -40,8 +45,11 @@ public void NamesConvertedFromInstalledToInstallingDoNotHaveInstalledPostfix()
         [Fact]
         public void UniqueNamesConvertedFromInstalledToInstallingAreStillUnique()
         {
+            // A snapshot name created 1 microsecond (10 ticks) later must be different
+            var waitTime = new TimeSpan(10);
+
             var name1 = DependencySnapshotFolderNameTools.CreateUniqueName();
-            Thread.Sleep(2); // A snapshot name created 2 milliseconds later must be different
+            Thread.Sleep(waitTime);
             var name2 = DependencySnapshotFolderNameTools.CreateUniqueName();
 
             var convertedToInstalling1 = DependencySnapshotFolderNameTools.ConvertInstalledToInstalling(name1);