A tester just needs to master the art of understanding their product & then file bugs based on their findings right? Wishful thinking! You better have the technical understanding of the code your developer is writing if you intend to properly test it.
So understanding how your product works is a good start, but as mentioned earlier a tester needs to have breath & be able to go deep. Part of that depth is understanding the code behind their product.
There are a couple examples of why you will need to have this depth:
While development is designing & implementing the product you will need to figure out how you are going to test the product, while also being involved in the product design itself. Understanding how the code is implemented is going to help with designing your automation. For example if you have a typical 3 tier application, how is the UI talking to the middle tier? Are those APIs public? Do they give you what you need to write automation? How can you extend them for what you need? Is there a better way to design the product to make it more testable?
Part of being a tester means you are one of the first customers of your product. You are developing tests against a moving target as developers are implementing new features & making changes. One day a test may be passing & the next it fails. Is it a test issue or a product issue that is causing it to fail? Your product may not have much manageability yet so there are no good events in the log that you can use. The only thing left is being ready to strap a debugger to the product & step through the code to understand where things are going wrong. If it is a product change that broke your tests you may need to understand how to update your tests to work again. Oh & when you are done, you’ll want to file a bug to improve the manageability of the product. You are doing something a customer would be doing and they won’t be able to strap a debugger to it. You’ll want enough information in the logs that ideally a customer could resolve the problem.
So you now know your product’s code inside & out. You are able to debug & even provide your developer with proposed fixes. You might even have helped write some of the features in your product. Now forget everything you know about the code.
What?! You might say, I worked so hard to figure it all out. Yep & if you are not careful you may make some of the same assumptions that the developer did when they wrote the feature. That means you run the risk of designing your test cases around the code & missing some juicy bugs. You need to step back & challenge any and all assumptions that you might be making.
Along with challenging the assumptions made in the code, don’t forget to challenge & look at everything from the customer’s eyes. Does the instructions we provide in the UI make sense to the end user or are we using 3 different terms to reference something because it’s name has changed over the course of development. One powerful tool here is to swap features with another tester & try each other’s area out. If they can’t figure out how to use your feature, don’t dismiss it as they are new & don’t understand the product enough. They are likely stumbling over some areas that a real customer would & since you are neck deep in your feature & code, of course how to use it is obvious to you. It likely won’t be obvious to your customer, so look for how you can improve that also.