03 Automated Tests.md

Add an automated test

I'd already begun moving on to the next stages when I realised that I was failing at one of my objectives. I had tested the Azure Function locally with the func command, and a web browser - but of course I wouldn't remember to do that every time I made a change. I need to have checks like that done automatically (or at least automated).

So, time to add a test project.

mkdir WordValues.Azure.Tests
cd WordValues.Azure.Tests
dotnet new xunit --language F#

That produces an F# project using xUnit as the test framework.

Testing under func.exe

Http-triggered functions can be tested by connecting to the endpoint that is created when func start is used in the Azure Function project's source folder.

To do this, we can use xUnit's class fixtures

• Run func start in the class fixture with a known port.
• When a test needs to access the function, check the func.exe process has not exited, and try to connect to that port. If all is ok, return some connection context.
• When the fixture is disposed, kill the process we started.

Testing the Http-Triggered function

In the test case, we can use the class fixture to get the base Url (which will check that the hosting process hasn't gone away)

FsHttp provides helpers to make the request/response code simple, and then the status code and response body can be checked in the test.

It's a slow test to run compared to real unit-tests, but it's faster than running func manually and pasting urls into the web browser, and it can be done automatically by just running dotnet test