ConfigureWindowModel.GetErrors C# (CSharp) Method

    public string GetErrors()
    {
        var stringBuilder = new StringBuilder();
        if (IncludeAttributeAssembly)
        {
            if (string.IsNullOrWhiteSpace(DependenciesDirectory))
            {
                stringBuilder.AppendLine("DependenciesDirectory is required if you have selected IncludeAttributeAssembly.");
            }
        }
        if (!DeriveTargetPathFromBuildEngine)
        {
            if (string.IsNullOrWhiteSpace(TargetPath))
            {
                stringBuilder.AppendLine("TargetPath is required if you have selected DeriveTargetPathFromBuildEngine.");
            }
        }
        if (string.IsNullOrWhiteSpace(EventInvokerName))
        {
            stringBuilder.AppendLine("EventInvokerName is required.");
        }
        if (string.IsNullOrWhiteSpace(ToolsDirectory))
        {
            stringBuilder.AppendLine("ToolsDirectory is required.");
        }
        if (string.IsNullOrWhiteSpace(TargetNode))
        {
            stringBuilder.AppendLine("TargetNode is required.");
        }
        if (stringBuilder.Length == 0)
        {
            return null;
        }
        return stringBuilder.ToString();
    }

 public void ValidateTargetPath()
 {
     var model = new ConfigureWindowModel
                     {
                         TargetPath = null,
                         DeriveTargetPathFromBuildEngine = false,
                         ToolsDirectory = "foo,"
                     };
     Assert.IsNotNullOrEmpty(model.GetErrors());
     model.TargetPath = string.Empty;
     Assert.IsNotNullOrEmpty(model.GetErrors());
     model.TargetPath = "a";
     Assert.IsNull(model.GetErrors());
 }