On no longer wanting to depend on ExpectedConditions in my C# Selenium WebDriver tests
Those of you that have been writing tests with Selenium in C# for a while might have noticed that as of version 3.11, some often-used things have been marked as deprecated, most notably the
PageFactory implementation and the
ExpectedConditions class. For those of you that have not read the motivation behind this, here is the rationale behind it, as written by Jim Evans, core contributor to the Selenium C# bindings.
These implementations have been moved to a new location and have been made available as separate NuGet packages (
DotNetSeleniumExtras.WaitHelpers, respectively). As of the time of writing this blog post, however, there’s still no new maintainer for this GitHub repository, meaning that there’s no support available and no certainty as to its future.
And while that is no problem yet, since you can still use the deprecated classes from the Selenium bindings or use the
DotNetSeleniumExtras packages, I think it’s a risk to keep on relying on code that is effectively unsupported.
In my case, for
PageFactory, that’s not a problem, since I don’t typically use it anyway. For
ExpectedConditions, however, it’s a different story. When I’m writing and teaching Selenium automation, I’m pretty much still following the general approach I described a couple of years ago in this post. It still works, it’s readable, easy to maintain and explain and has proven to be effective in many different projects I’ve worked on over the years.
However, it also relies on the use of
ExpectedConditions, and that’s something that is bothering me more and more often.
So, while preparing for a training session I delivered recently, I started looking for an alternative way of writing my wrapper methods in C#. And it turns out that C# offers an elegant way of doing so, out of the box, in the form of lambda expressions.
Lambda expressions (also known as anonymous functions) is a function that’s not bound to an identifier, but instead can be passed as an argument to a higher-order function. The concept stems from functional programming (it has been a long while since I’ve done any of that, by the way) but has been part of C# for a while. By the way, lambda expressions are available in Java too, from Java 8 onwards, for those of you not working with C#.
Let’s look at an example. Here’s my implementation for a wrapper function around the default Selenium
SendKeys() method that takes care of synchronization and exception handling using
Here’s the same wrapper, but now passing a lambda expression of our own as an argument to the
Until() method instead of a method in
From the Selenium docs, we learn that the
Until() method repeatedly (with a default but configurable polling interval of 500 milliseconds) evaluates the lambda expression, until one of these conditions applies:
- The expression returns neither null nor false;
- The function throws an exception that is not in the list of ignored expressions;
- The specified timeout expires
This explains why I created the lambda expression like I did. Before clicking on an element, I want to wait until it is clickable, which I define as it being both visible (expressed through the
Displayed property) and enabled (the
Enabled property). If both are true, I return the element, otherwise null. If this happens within the timeout set, I’ll clear the text field and use the standard
SendKeys() method to type the specified value. If a
WebDriverTimeOutException occurs, I’ll handle it accordingly, in this case by failing the test with a readable message.
Yes, implementing my helper methods like this makes my code a little more verbose, but you could argue that this is a small price to pay for not having to rely on (part of) a library that has been deprecated and of which the future is uncertain. Plus, because I define all these helpers in a single class, there’s really only one place in my code that is affected. The Page Objects and my test code remain wholly unaffected.
This GitHub repository contains a couple of runnable example tests that are written against the ParaBank demo application. This is an updated version of the solution described here. An updated version of this last blog post is coming soon, by the way, so that it reflects some opinions and preferences of mine that have changed since I wrote that one. No longer having to rely on
ExpectedConditions, as I discussed here, is but one of those changes.