Continuous Development – OPA and Postman, Newman and Jenkins #3
Following on from the two previous episodes, (part one / part two) the stage is almost set to move to automation over and above the simple concept of a Postman Collection. In this chapter we will see how to use data files in Postman to facilitate making use of CSV or JSON data in a dynamic way, and we will get Newman up and running. So let’s start with the first element.
In our Collection, we currently have one request which is sending information to OPA and getting a journey time and plan back in response. Great. But we want to test our journey planner with more than one journey. And we want to be able to easily change the journeys without having to mess with our request. So this is where the ability to load data into a Collection from a text (CSV or JSON) file comes in very handy in deed. In pictures
- Create a CSV file with your data in it. For the project used in this example we would need to have something like this
Notice the headers are origin and destination. They will become variables that we need to add to our request.
- Make sure that the request is updated
So now my request looks like this:
Don’t forget to save your request. Now if you go to Collection Runner and run your Collection, you can use the Select File button and select your file:
As soon as you select the file, you will see that the number of iterations changes to take into account all the rows in your file. Now when you want to push a new set of journey tests all you need is to change that file. Awesome!
Armed with all of this, we can now move to the next challenge. Postman is great but not everyone wants to use the graphical user interface all the time. How about the ability to run a Collection from the command line? That would be great AND would open up lots of options to running Windows Scripts and the like. Well, the news is good. Newman is the CLI (Command Line Interface) for Postman. Setting it up if you are not familiar with Node.js can be a bit daunting, but let’s just make a shopping list first:
- Install Node.js (here)
- Install Newman using the Node Package Manager
This step should be as easy as opening the Node Command Prompt (which got installed in your Windows Start Menu in the first part) and typing something like the following:
- Run Newman from the Node.js prompt to use Postman Runner with your chosen Collection and Data File using the ultra simple command line.
So the last step might look a little like the following – notice that in the command line you specify the Collection (which you must first export to a file from inside Postman) and the Data File (wherever it is – I put both files in the same location for ease of use. And once the job is done, Newman reports back with it’s own inimitable, Teletext-style display of the output. A word of advice – before exporting a Collection make sure you have saved all the recent changes!
Once the Collection is exported, you might run it like this. This is just a simple example. It is possible to also load environment variables and more to fine tune it.
After a few seconds we get the output from Newman. Note the 4 iterations, and that iteration 3 failed due to an excessively long journey time.
Now this is of course a major step forward – running Collections from the command line, feeding in data sets just by using a simple command line switch – these features mean we can really now start to think of automation in our approach to testing this project. But we are not done yet. The output from Newman is pretty ugly and we need to change that. By installing Newman HTML Reporter, we can get a much nicer file. Follow the steps in the link and then change your example command line to something like this:
Note the new command line option -r html (which means, use the HTML reporter) and the –reporter-html-export option (with two dashes) which ensures the output file is stored in the folder of my choice. And the HTML output is so much better:
What a nice document. So far so good. We can spin these collections with just a command line. But wait a minute, what about running tests when you are not in the office – sure, you could write yourself some sort of Powershell Script in Windows. But what if you wanted to run a set of tests every day at 3pm, then again on Tuesdays, then once on the first Monday of every second month…it would get quite hard. And what if you wanted to send the HTML Report automatically to all your colleagues on the testing team…but only if there were failures?
And so, we march onward to the next phase. See you shortly!