gclo.Engine.Tests/AccountWizardViewModelTests.cs

@@ -280,6 +280,26 @@ public sealed class AccountWizardViewModelTests : IDisposable
 
 
 
+   [Theory]
+   [InlineData("")]
+   [InlineData("   ")]
+   public async Task TryAdvance_WithNoTokenTyped_AsksForOne_AndAsksNothingOfTheServer(string typed)
+   {
+      AccountWizardViewModel wizard = NewWizard();
+      wizard.Name = "Work";
+      await AdvanceToStepAsync(wizard, 2);
+      wizard.Token = typed;
+
+      Assert.False(await wizard.TryAdvanceAsync());
+
+      Assert.Equal(2, wizard.Step);
+      Assert.Equal("Enter a token to continue.", wizard.TokenError);
+      Assert.False(wizard.IsValidatingToken);
+      Assert.Equal(0, _orgs.Calls);
+   }
+
+
+
    [Fact]
    public async Task TryAdvance_RejectedToken_SetsTokenErrorAndStays()
    {

gclo.ViewModels/AccountWizardViewModel.cs

@@ -368,6 +368,13 @@ public sealed partial class AccountWizardViewModel : ObservableObject
                         return false;
                      }
                   }
+                  else if(candidate.Length == 0)
+                  {
+                     // Nothing to check: say so here, instead of asking the server
+                     // and showing its argument error (#172).
+                     TokenError = "Enter a token to continue.";
+                     return false;
+                  }
                }
 
                IsValidatingToken = true;