Top-5 reasons to use both manual testing and test automation: when and what type to use

Testing is an essential part of any software development project. The quality of the application and accordingly its success with the end-user depends on it. Testing is divided into two key types: manual and automation. Nowadays the most effective way to ensure the quality of an application is to combine both types of testing. In this article, we explain why this is the best option for product testing, as well as look at the features, advantages, and disadvantages of each type of testing, and find out when to use which type of testing.

Why do you need both manual testing and test automation?

Most companies, even having implemented and set up test automation, still use manual testing. Here are 5 key reasons why:

1. Manual testing and test automation are not 100% interchangeable. There are types of testing that are too difficult or impossible to do manually. There are also a number of tests that cannot be automated.
2. The combination of manual and automated testing provides maximum test coverage. So many companies have two test teams, one for manual testing and one for test automation.
3. A mix of two types of testing allows you to speed up the release without sacrificing quality. Automation allows you to increase the speed of testing at times. In turn, manual testing complements the process of test automation by discovering issues from the user’s perspective.
4. Maximum test coverage of various aspects of the same functionality is possible only with both manual testing and test automation.
5. Insurance against errors in automated test scripts. These errors can lead to false positive or false negative results. Manual testing allows you to check everything that is in doubt.

Now let’s figure out what manual testing and test automation are in detail.

What is manual testing

Manual testing is a process where software is tested manually, without any automation tools or scripts. Manual testers check whether the functionality of the application and its design corresponds to the test plans. Testers also develop test cases and implement them manually, and prepare reports based on the results of their execution. As a result, visible and hidden software defects are identified.

Pros and cons of manual testing

They say test automation will soon completely replace manual testing. Despite this fact, it is very likely that manual testing will never go away. Here are proofs:

• Not all tests can be automated. So manual testing will exist. 
• Manual testing is very flexible. Modern teams need to be flexible and work as quickly and productively as possible. They must have the capacity to respond to the slightest demand for change immediately. Manual testing allows you to quickly adapt to any emergency.  
• You do not need to invest in additional tools. Manual testing can be performed by team members or hired specialists. It does not require large upfront costs and simplifies budget management. 
• Feedback. Everyone knows that application code can contain bugs. Automated test code can also be imperfect. If a QA automation engineer writes tests with bugs, then the team will get false positive/negative results in return. For this reason, manual testing is ideal for the early stages of development. Errors in automated tests and scripts in the early stages of development cause great problems and inconvenience for both the development team and end-users. 
• Manual testers interact with the application like real users. Thus, they are more likely to find critical problems in the functionality and interface. 
• Deeper testing of the user interface. Manual testing allows you to more reliably assess how well the application works in terms of visual aspects. Manual testers check how the application’s pages/screens look after a series of user actions. They also help reduce the chance that certain visual elements may be misleading to users.

Despite these advantages, manual testing is not a universal testing type. The main disadvantages of this type of testing are:

• Higher error rate compared to automated testing. Due to the human factor, many bugs can go undetected and then affect the end-user experience. This is especially true for repetitive tests. They are very time-consuming, so they are difficult to perform manually. 
  
• Time-consuming process. The speed of manual testing directly depends on how many people are involved in testing. In the long run, manual testing can be more resource intensive. 
• Not suitable for many types of testing. For example, regression and performance testing are types of testing that are not suitable for manual execution.

What is test automation 

Test automation is a type of testing in which tests are executed using automation tools and scripts.  Automation allows you to carry out in cases where manual testing is too time-consuming or not suitable for other reasons. 

Pros and cons of a test automation 

As you know, automation increases the efficiency of software development in terms of saving time and human resources. Here is a list of the key benefits of test automation:

• Cost-efficiency for large projects. In the long run, test automation is more cost-effective than manual testing. This is despite the fact that it requires a higher initial investment. If you apply test automation correctly, ROI will be more pleasant for stakeholders in the long run. 
• Test coverage. Automation provides more accurate and relevant results, and allows you to distribute workload across the team better. You can run tests on different versions of the application (mobile, web, desktop), on different devices with different configurations, on different browsers. Automated scripts unnoticed execute thousands of complex test cases during each test run. All this provides a level of test coverage that is not possible with manual testing alone.  
• Faster results. Since test automation is performed by software tools, it is completed much faster than manual testing. In addition, you can save test sessions to reuse them in other scenarios.  
• Simple reporting. Creating reports can be very time-consuming if you do it manually. Test automation tools generate beautiful and understandable reporting within minutes. 
• Tools for execution and analytics. When you implement test automation, there are numerous tools and platforms that can maximize the benefits of automation. Zebrunner is one of the best examples of such tools. It helps you to implement test automation in a project without much difficulty and achieve significant savings in time and money. The support team will advise you which tool functions are most convenient and beneficial for your product. A flexible payment system allows you to pay only for the time you use the tool. Beautiful and convenient reporting helps you to understand the state of the testing process not only for QA specialists but also for people without a testing background.

However, test automation faces certain challenges that you need to be aware of in order to ensure the highest possible quality of the project.

• High price for small projects. Test automation tools have various capabilities and limitations. In addition, it is necessary to constantly maintain automated tests, their maintenance, which also entails additional costs. The cost-effectiveness of test automation is not something you get instantly. It takes time and effort to get it, and it can be costly for smaller projects. 
• Lack of human expertise. Human expertise is invaluable when it comes to product usability and user interface feedback. When automated tests are performed, very little human intervention is required. In turn, the test script can only act as it is configured. So sometimes script can omit mistakes that would be obvious to a manual tester.

The difference between manual testing and test automation 

In manual testing, the tester executes test cases manually. He describes scenarios and edge cases and then tests them.

In test automation, this work is automated. Scripts and tools are used that, once configured, automatically perform the steps required to test the script.

Key differences between the two types of testing by parameters:

Parameter	Manual testing	Test automation
Time	Time-consuming.	Execute tests much faster than manual testing.
Accuracy	High probability of errors due to the human factor.	More accurate and reliable results for automated tools and scripts.
Human observation	Human observation and usability assessment from the end-user’s point of view.	Human intervention in test execution is minimal, which can eventually lead to usability issues.
Investment	Not high or absent. Expenses go to pay for human resources.	High initial investment required to pay for automated testing tools and for human resources.
Programming skills	Manual testers may not have programming knowledge.	Programming knowledge is required.
Test report visibility	Manual test results are usually recorded in Excel or Word, results are not always available.	The reporting is clear to all stakeholders, any of the managers can check the test results even if they do not have a technical background.
Parallel execution	It can be executed in parallel only if more people are involved in testing.	They can be executed in parallel on different operating platforms, devices, browsers.

When you should use manual testing and test automation 

As a summary, let’s consider when manual testing is preferable, and when test automation (here we agree with how Vilmate blog looks at it).

Manual testing is the best for:

Exploratory testing. Studying the functionality of a new product from different perspectives is only possible through manual testing. This allows you to inspect a wide range of paths, thus identifying defects that would otherwise be missed by scripts. Exploration is a manual process, any member of the project team can contribute to it. Specialized knowledge for test automation is not required here, but the opinions of different team members are welcome. New functionality that is still in development and is gradually evolving and changing needs testing, but automated tests are not yet viable here.

Usability testing. Testing for usability is something that can potentially be automated, but the execution by a human is more effective in this case. The absence of disappointment is the main criterion that helps to decide whether a product is convenient or not. And this is a subjective assessment that should follow specific guidelines for making decisions about usability issues.

Random (monkey) testing.  It is performed informally, with the aim to find out any loophole in the system. Random testing can only be performed manually. Unlike test automation, which only tests what is predictable and proves that the program works as expected through the combined efforts of automated test developers, manual random testing is convenient in a different way. It allows the tester to act as a real user who can find bugs through (pre)guessing bugs. If applied individually, specialized testing will not be sufficient to ensure software quality, but it will add support for other QA activities. Sometimes this method can be mixed with exploratory testing. The former, however,  focuses more on negative testing.

Short-term project testing. It’s not a good idea to start automated tests when the project is planned as a short-term effort. Manual testing will be enough to meet the basic needs of such a project. This can lead to wasted resources and automation becomes useless. Automation means higher maintenance and management costs, as well as additional man-hours, scripting, rewriting, which may not balance with the potential ROI of a small project.

Test automation is the best for:

Regression testing. Test automation is a good option to check if already existing versions of an application can work after a new version of the application is released. By automating regression testing, the QA team can count on benefits such as increased test coverage, recurring test results, increased test efficiency due to faster test execution, and continuous use of regression tests. 

Performance testing. The execution of load tests should be supported by automation tools. For example, if you need to simulate the use of an application by any number of concurrent users, automate this process. There are no viable manual alternatives here. The QA team creates load test scripts and develops the corresponding test scripts. End-user behavior is simulated with scaling loads up to thousands of concurrent users. This way you understand how well the application performs under load, and see the problems that the end-user may have.

Repeatable functional test cases. The ability to spare manual testers from repetitive execution of the same tests is the basis for the cost-effectiveness of automation. Routine, repetitive tests should not be performed manually. This is time-consuming and a resource for many bugs. If the task does not change on different test cycles, then it can be executed by scripts.