Why?

Testing is a crucial aspect of modern software engineering and therefore it is important in Network Automation. FakeNOS solves the problem of testing scripts in a lightweight and easy to use manner. It allows to create a test environment with multiple devices running different Network Operating Systems (NOS) in a matter of minutes.

Problem with integration testing

A crucial aspect of writing applications or scripts for Network Automation is testing. Often testing is done using physical or virtual instances of network appliances running certain version of Network Operating System (NOS). That approach, while gives best integration results, in many cases carries a lot of overhead to setup, run and tear down as well as putting significant burden on compute and storage resource utilization.

As well, many times it happens that the vendor does not give access to the device for testing purposes or that you do not have the image to run in a virtual environment. In such cases, it is very difficult to test the application or script that you have written.

As well, in case that we want to create a test environment with multiple devices running different NOS, it is very difficult to setup and run such environment. Even though tools like GNS3 or EVE-NG exist, they are not always the best solution for testing purposes.

Problem with Unit testing

Another approach is to mock underlying libraries methods to fool applications under testing into believing that it is getting output from real devices. That approach works very well for unit testing, but fails to simulate such aspects as connection establishment and handling.

Also, the main problem with such approach is that you need to specify the output for each command that you want to test. This is very time consuming and not always the best solution.

Our approach

FakeNOS positions itself somewhere in the middle between full integration testing and testing that mocks device interactions. FakeNOS allows to create NOS plugins to produce pre-defined output to test applications behavior while running servers to establish connections with.

It does so in a lightweight and easy to use manner. You can create a test environment with multiple devices running different NOS in a matter of minutes. It is simply a python library which spin up SSH server and fakes the output of the commands that you specify.

Note

In the current approach, the output is predefined and will always be the same and replies to the same exact command. There is on going effort to infer the commands (similar to ntc-templates) and make the output dynamic (using Jinja2).