Selenium is a common integration test framework popular with C# developers. With the MailSlurp DotNet SDK you can send and receive emails from code and tests.

If you write .NET applications you probably deal with email addresses at some point: for user sign-up, email newsletters, password resets and more. If you want to test this functionality end-to-end you need test email accounts.

MailSlurp is a free API that lets you create email addresses in C# then send and receive emails with them. This article will show you how to test a web applications user sign-up using Nunit, .NET Core 2.1, Selenium and Firefox Gecko Driver.

Example application

For an example of using emails in selenium with .NET we will use a dummy web app hosted at

This app has a real sign-up process. It lets users sign-up with an email address, then it sends them a confirmation code via email. The user can then submit the confirmation code and confirm their account. Finally the user can sign in and see a welcome screen.

We'll test this process end to end. Full source code available on GitHub.

Writing a test

To test the Playgrounds authentication process with real email addresses lets set up a .NET Core 2.1 project.

MailSlurp's CSharp Package on NuGet supports .Net Core 2.x and 3.x. If You need another target consider the REST API.


First you need Firefox and the Selenium Gecko Driver. You can install them with or download them manually and add them to your Path.

Add project dependencies

Create a new .NET Core project and add the following dependencies in :

Create test file

Next create an Nunit test:

Next we need to configure Selenium. We will add a FirefoxDriver and tell it to start before our tests. Then we'll add a shutdown method after the tests have finished. Put the following inside the class:

Test loading the playground

Now we can write some tests. So let's load the playground app and click the sign-up button:

Create test email accounts

Next we need to start a user sign-up. We will need a new test email account first. Create one with MailSlurp then use it to fill the sign-up form:

If we run the test the result should look like this:

Receive confirmation email

Once the sign-up form is submitted the playground app will send a confirmation code to the email address. We can wait for the email to arrive using MailSlurp.

Extract content and confirm

Next let's find the verification code in the email and submit it to the confirmation screen:

Running the test should look as follows:

Sign in with confirmed user

Finally we can test that a confirmed user can sign in. Load the playground again and sign in.

The login should look like this:

Once logged in the user will be greeted with a welcome message.

Next steps

Selenium is a powerful testing tool. When combined with test email accounts you can test email related processes end-to-end. MailSlurp is free email API with C# bindings. Check out the documentation to get started.