Add unit test that proof setting TabIndex before all views are added, will have unexpected result.

UnitTests/View/NavigationTests.cs

@@ -1312,6 +1312,32 @@ public class NavigationTests
         Assert.True (r.Subviews.IndexOf (v3) == 2);
     }
 
+    [Fact]
+    public void TabIndex_Invert_Order_Added_One_By_One_Does_Not_Do_What_Is_Expected ()
+    {
+        var r = new View ();
+        var v1 = new View () { Id = "1", CanFocus = true };
+        r.Add (v1);
+        v1.TabIndex = 2;
+        var v2 = new View () { Id = "2", CanFocus = true };
+        r.Add (v2);
+        v2.TabIndex = 1;
+        var v3 = new View () { Id = "3", CanFocus = true };
+        r.Add (v3);
+        v3.TabIndex = 0;
+
+        Assert.False (r.TabIndexes.IndexOf (v1) == 2);
+        Assert.True (r.TabIndexes.IndexOf (v1) == 1);
+        Assert.False (r.TabIndexes.IndexOf (v2) == 1);
+        Assert.True (r.TabIndexes.IndexOf (v2) == 2);
+        // Only the last is in the expected index
+        Assert.True (r.TabIndexes.IndexOf (v3) == 0);
+
+        Assert.True (r.Subviews.IndexOf (v1) == 0);
+        Assert.True (r.Subviews.IndexOf (v2) == 1);
+        Assert.True (r.Subviews.IndexOf (v3) == 2);
+    }
+
     [Fact]
     public void TabIndex_Invert_Order_Mixed ()
     {