When to Use Manual and Automation Testing: A Quick Guide

Timothy Joseph Timothy Joseph | February 21, 2019

When to Use Manual and Automation Testing: A Quick Guide

The existence of both manual and automation testing gives the illusion of choice.

Technically, you can view them as interchangeable, that one is the faster version of the other. Once you understand how each QA testing approach operates, its strengths and weaknesses, you find there is no choice. Instead, the idea is to know when to apply them, not if you should choose one over the other.

Knowing when to use manual and automation testing is really just an understanding of your product. If you know the parameters and scope of the QA process ahead of you, then knowing when to deploy each method becomes obvious.

We have put together a quick guide to understanding each approach that should help you identify the approach that best suits the components of your testing process.

When to Use Manual and Automation Testing

You can access the relative strengths of automation and manual testing only if you have a comprehensive understanding of your product. Every QA process begins with a scoping study, selecting the right framework, and employing the right metrics. You have to understand where it is possible and practical to apply each testing approach before making decisions related to ROI.

With that groundwork in place, you are ready to maximize the strengths of manual and automation testing.

When to Use Manual Testing

Manual testing is the best way to get the impressions, demands, and reactions of human beings. Even when your test scripts are written by domain experts, the process falls short of the human engineer’s ability to see through bugs into fixes, or to realize the difference between what is functional and what is optimal. Manual testing is best when simulating the user experience. As long as your end-users are humans, there is an advantage to using human QA engineers.

The same mental gymnastics a human engineer can perform while standing in the user’s shoes can also be brought to bear on the security aspects of the QA process. It is recommended that the majority of your cybersecurity simulations, from DDoS attacks to penetration testing, be carried out manually. Human engineers are better at determining where attacks are likely to succeed.

Essentially, manual testing is a preference to qualitative testing. Where the release cycle permits, you want to have human engineers completing the following test phases:

  • User Interface Testing

  • Usability Testing

  • Installation Testing

  • Security Testing

  • User Acceptance Testing

The conclusion to understanding when to use manual and automation testing is acknowledging that your QA process is stronger when you use both.

When to Use Automated Testing

Automation puts more power in the hands of your developers and QA engineers. It is proven to increase the accuracy and coverage of your test cases and saves time in your release cycle. Those benefits let your engineers focus their time and your resources on higher-value tasks. It keeps QA teams lean and allows you to control costs by removing repetitive tasks from human hands—and test scripts don’t suffer from fatigue.

It sounds perfect, but there is a catch. Automation cannot be applied to every test case or to every test phase. Automation trails manual testing in user acceptance, interface, and usability testing.

There is still a way to use automation to produce ROI quickly. You just have to know when it should be applied. Automation can reduce testing time by up to 95% when used to analyze huge quantities of data. It is built for scale and speed, and the more information you can feed, the more efficiencies you create.

As such, automation is best for the following test phases:

  • Regression testing

  • API integration;

  • Repetitive smoke tests;

  • Scalability;

  • Build acceptance testing: Tests that need to be run with every build of the application, which will save a great deal of time if automated (e.g., smoke tests, sanity tests);

  • Frequent testing areas: Areas that need frequent testing (e.g., smoke, sanity, and regression tests) are best automated. This leads to faster feedback and shortened release cycles;

  • High business-relevance tests: Regression Tests with high business relevance should be targeted for automation. Tests that target revenue areas (i.e., payments, transactions, etc.);

  • API and DB automation: Automating API and DB tests would increase product robustness and reliability;

  • Failure-prone areas: Areas that have high probability of failures should be automated, as should those which will get heavy use;

  • Time-consuming areas: Automation of time-consuming tests, such as those that require bulk data generation;

  • Data-driven tests: Automate tests that need to be run identically on different sets of data. That will reduce the risk of failures from human error;

  • Precision-testing: Tests requiring a great deal of precision should be automated and will also reduce the risk of mistakes (e.g., Finance calculations);

  • All customer-reported defects also need to be automated on priority to avoid any future occurrence; and

  • Any test cases across multiple configurations need to be automated on priority, as this leads to time saving.

Theoretically, you can apply automation testing to any phase of your QA process, especially if you have skilled QA engineers who can write successful test scripts. However, you are unlikely to achieve 100% test coverage. To meet that goal, you need manual testing as well.

Combining the Strengths of Manual and Automation Testing

Knowing when to use manual and automation testing together is at the core of your QA process. Essentially, the approaches split on a qualitative versus quantitative basis.

You want to use automation testing on those aspects of your product that require repetitive testing of large quantities of data. It works release cycle wonders in functionality and core stability testing.

Manual testing, on the other hand, is best deployed when your engineers can simulate the user experience. You do not have to wait until the GUI phase to implement it either. Human engineers can make a valued contribution by catching bugs as early as possible.

Every QA process includes phases that favor one or the other test approach. The trick is to have the support and talent on hand to implement each when needed.

QASource’s engineers are experts in both automation and manual testing. With more than 1,000 years of collective experience, our engineers can show you how to optimize your QA process by utilizing the strengths of each approach. Contact us today for a free quote: Email info@qasource.com or call +1.925.271.5555 to get started.


This publication is for informational purposes only and nothing contained in it should be considered legal advice. We expressly disclaim any warranty or responsibility for damages arising out of this information and encourage you to consult with legal counsel regarding your specific needs. We do not undertake any duty to update previously posted materials.

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