Top Hard Skills for Quality Assurance Engineers

The in-demand QA engineer has to deal with modern application architectures that resemble a layered pie. And the number of layers varies depending on the application's functionality and how the current team decides to implement it.

What skills are needed for QA projects? A specialist needs to be familiar with the architecture of applications that can work separately and as a whole. Otherwise, the QA engineer will not be able to do comprehensive testing.

We will discuss the vital complex skills of QA with an example of a three-tier architecture model. 


Quality assurance skills list for presentation layer testing

A poor user experience can cost you new customers who won't want to interact with your web or mobile app. Presentation layer testing allows you to find graphical user interface (GUI) defects and fix them in time.

When testing the presentation layer, a professional QA engineer can't do without the following:

  • Knowing the recommendations of platforms and client companies
  • Keeping abreast of the latest GUI trends
  • Understanding of site structure, HTML/CS, and JavaScript basics
  • Experience with multiple browsers and devices
  • Understanding of system development life cycle processes (SDLC).
  • Mastery of all of these skills is vital to a quality QA professional, but why?

The GUI testing process defines mandatory skills and competencies, as a QA engineer must address a number of specific tasks:

  • Verify the structure of system elements
  • Verify compliance with platform guidelines
  • Approve the page layout and how it displays on different devices with different settings
  • Ensure compliance with approved design and requirements
  • Evaluate the usability of the interface
  • Perform localization testing
  • Perform A/B testing

You can handle these tasks with test cases written based on the approved page design and updated requirements. I have practical tips for you in my article on how to write test cases that will work for you.

For writing simple automation scripts for presentation-level testing, I recommend using recorders such as Katalon, TestCraft, and TestingWhiz. Each option has a graphical interface, supports real-time script creation, and allows you to dive into the code and become familiar with the automation.

Using recorders, you can create sequences of user actions as a script, similar to the way you create macros in MS Word applications or actions in Adobe Photoshop. These scripts can be replayed later.

But there are more complex tasks. A professional QA engineer must master skills specific to object-oriented programming. So your basic skill set should include Java, C, or Python along with various frameworks including Appium, Selenide, TestNG, Maven, Zebrunner, or others.

Manual QA engineers use a "black box" approach to test the quality of data processing modules. They focus on verifying that all modules, including server, database, and services, are working correctly. The data and specifications they get in the task documentation are all they have as input. And they use that data to evaluate test results.

Black-box testing allows QA professionals to look at an application from the perspective of the average user. But sometimes, diving into the details is just necessary.

You may need to scrutinize the source code to trace a bug back to its root cause. White-box and gray-box methods allow you to drill down into the details of the source code. Using these approaches, you can reduce testing and debugging time if your coding skills and knowledge of object-oriented programming allow it.

How can white-box or gray-box testing change the game?

For example, you need to test a data entry field using black-box testing. You make a matrix of possible input choices, both correct and incorrect, and try that matrix as soon as the build is complete.

Is the wait too long? You can use the "gray box" testing method. It allows you to narrow down the number of input options depending on the variable used in the code - int, double, or others in Java. You can also check to see if there is an error handling block before you start building. This way, you will save time fixing bugs, performing acceptance testing, and completing regressions.

What about API and microservice testing?

To test APIs, professional quality assurance and testing engineers must understand REST and SOAP, which underlie the mechanics of modern applications. They must also know the pros and cons of data exchange formats such as JSON and XML and data transfer protocols such as HTTP and HTTPS.

If you need to test a microservice, you should focus on studying the documentation thoroughly. Before testing, I highly recommend reading the technical data on the developer's website to determine the specifics of the service. Study how the technology is implemented in reality and do not rely on theoretical knowledge.

Top 3 skills for QA professionals when testing databases

If you're looking to hire QA engineers or are on your way to becoming a database testing QA specialist, these skills are what you need:

  • The principle of how application components work together
  • Types and models of database management systems and principles of database construction and use
  • Basic commands and who uses them when working with SQL

How can this help you? Essentially, you have to do "black box" testing when your task is to check the parameters in the database. These parameters are displayed on the GUI or in the body of the query/response.

For example, your task is to test the users' email database. You may want to ensure that the form for adding emails works correctly and stores the email data in the pre-run step.

Test system functionality to detect and correct system errors when adding a new entity or other data through the user interface.

Use visual database design tools like Workbench or PostgreSQL to test how smoothly data entry and accessibility work.

You can also test the operation of data input and output using CRUD, although this will require some training or previous experience.


The best quality assurance engineers must keep up with current technology and methodologies. You need to develop a set of critical, necessary skills and in demand in the marketplace. This will make you an invaluable part of almost any QA team.

Remember, don't leave quality assurance skills just for your resume - you need to develop them. A quality focus on complex skills can allow you to spot opportunities to build a sustainable career in QA.

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