This turned out to be much simpler than I imagined. Once you’ve worked out how to use parameters (see last post), its as simple as creating two parameters: one for ‘username’ and one for ‘password’, and pointing JMeter to the login form’s POST URI.
For this particular test I used the ASX “MyASX” portal, due to it having a simple RESTful API and still using SSL.
A bit of digging at the home page with Chrome Developer Tools uncovers the RESTful URI: “https://myasx.asx.com.au/home/login”. Pointing JMeter to this URI, and setting parameters for username & password gives us a successful login.
Easy enough for someone with four years experience in web development, not so much for a small business owner trying to find bottlenecks in their website.