Skip to main content

Property based testing in C#–Part 5

This is the fifth post in my Property based testing in C# series. If you have missed my previous posts, you can check them here:

Through this series I used FsCheck to generate and run property-based tests. For every property I want to test FsCheck generates random input values. These values can be different between each test run meaning that each test run can end with different results. So if you had a bad input value that failed your test the previous time, it is possible that in a next test run you will not see this bad input again.

For simple input values this doesn’t have to be a problem, as you can have a look at the test logs to see the input that failed your test and than you can use this input to write an example-based test. But when you start using more complex inputs, it can be a lot more difficult to replicate the failed test.

Replay using the FsCheck seed

So how can we solve the problem above? If you take a look at the test output maybe you have noticed the StdGen(318823861,297138967) line. This is the seed value that FsCheck used for generating the input.

So if you want to use the exact same input in your test, you should use this value in your test by setting the Replay property on the Property attribute:

Labels:

Popular posts from this blog

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.
Read more

Kubernetes–Limit your environmental impact

Reducing the carbon footprint and CO2 emission of our (cloud) workloads, is a responsibility of all of us. If you are running a Kubernetes cluster, have a look at Kube-Green . kube-green is a simple Kubernetes operator that automatically shuts down (some of) your pods when you don't need them. A single pod produces about 11 Kg CO2eq per year( here the calculation). Reason enough to give it a try! Installing kube-green in your cluster The easiest way to install the operator in your cluster is through kubectl. We first need to install a cert-manager: kubectl apply -f https://github.com/cert-manager/cert-manager/releases/download/v1.14.5/cert-manager.yaml Remark: Wait a minute before you continue as it can take some time before the cert-manager is up & running inside your cluster. Now we can install the kube-green operator: kubectl apply -f https://github.com/kube-green/kube-green/releases/latest/download/kube-green.yaml Now in the namespace where we want t...
Read more

DevToys–A swiss army knife for developers

As a developer there are a lot of small tasks you need to do as part of your coding, debugging and testing activities.  DevToys is an offline windows app that tries to help you with these tasks. Instead of using different websites you get a fully offline experience offering help for a large list of tasks. Many tools are available. Here is the current list: Converters JSON <> YAML Timestamp Number Base Cron Parser Encoders / Decoders HTML URL Base64 Text & Image GZip JWT Decoder Formatters JSON SQL XML Generators Hash (MD5, SHA1, SHA256, SHA512) UUID 1 and 4 Lorem Ipsum Checksum Text Escape / Unescape Inspector & Case Converter Regex Tester Text Comparer XML Validator Markdown Preview Graphic Col...
Read more