Automated vs Manual Testing: Pros, Cons, and Which Is Better
Testing is an irreplaceable part of software development. Quality testing helps to battle security breaches, which currently cost companies about $25 per minute according to RiskIQ. In Agile methodologies, testing is a continuous process that starts right at the beginning of development. Today, testing can be done either manually or automatically. Let’s look into the manual testing vs automated testing dilemma. You’ll learn the advantages of automation testing over manual testing and vice versa, and get advice on where to use which testing approach.
1. What’s the difference between manual testing and automation testing?
Manual testing is performed directly by a quality assurance (QA) specialist who runs software through test scenarios built on requirements. QAs test one scenario at a time.
In automated testing, test scenarios are run by software, which often enables multiple scenarios to be tested simultaneously. However, for automated testing to work, the test scenarios need to be prepared by an automation quality assurance specialist, so automated testing isn’t free from human involvement. To enable automated testing, a QA writes scripts in a programming language of their choice — generally Python, C#, or Java. Those scripts are then launched using tools such as TestComplete, Selenium, or Appium. Software runs tests faster than a human but needs a human to work.
Finally, not all tests can be run by software.
2. Benefits of automation testing
Why do we strive to automate everything in the first place? Because it (a) frees our time to do more fun and more important things and (b) lets us accomplish our goals faster. This applies to software development as well. However, there’s more to software testing automation.
2.1. Automation saves time on otherwise time-consuming tasks
Testing software can take a lot of time and is often repetitive — for example, when checking if an application acts the way it’s supposed to after an update to the app itself or the operating system. Both iOS and Android are updated frequently, and sometimes those updates affect features in applications. If an update affects features your app uses, you need to test those features to make sure your app works properly with the latest version of the operating system.
Such repetitive tasks can be done manually, of course, but they take a lot of time from QAs. Instead, a QA can create algorithms to run these repetitive tests automatically while the QA works on testing new features. A script can run tests up to five times faster than a person — and the QA will complete some none-automated tasks or write more scripts at the same time.
Moreover, automated tests can run 24/7, whereas manual testing specialists generally work a traditional eight-hour day five days a week.
Example: Regression tests are repeated after each update to a feature, an app, or an operating system. These tests check if the update creates a bug or conflict between features. It takes a lot of time for a QA to manually run and re-run these tests after each update.
A QA automation specialist can write a test script once and run tests as many times as necessary. While these tests are running, your manual and automation QAs can be busy testing other features.
2.2. Automation can help battle human error
People make mistakes and may miss things. Machines, when correctly programmed, don’t make mistakes. And when there’s a mistake in test code or its execution, you’ll instantly know it as the test will fail. With automated testing, there’s no “it seems to work as expected” — it either works or it doesn’t.
Example: Due to a lack of time or specialists, manual QAs can miss small signs of bugs in features. Such bugs can lead to truly epic failures, and fixing them at later stages of development will cost much more time (and money) than fixing them early on.
This scenario can’t happen when a computer runs the tests because computers (a) run tests faster than people and (b) don’t get distracted, tired, or too used to the code.
2.3. Automation can save money (if applied correctly)
This one is seemingly simple — when a QA spends less time on a task, it costs less. In debates on manual vs automated testing, this fact often comes up. And it’s true to an extent: in the long run, automating what can be automated will most likely save you a lot of QA work hours and, hence, a lot of money.
However, there’s another side to the coin, as automated testing software costs money as well. For this reason, testing automation is often used on big projects rather than short-term projects where there’s little to gain with it.
2.4. Some tests can only be performed with automated testing
When it comes to testing big applications that are supposed to be used by lots of people at the same time — video conferencing or streaming software, online educational tools, or popular games — manually testing their performance under stress is practically impossible. Tests that check if an application can withstand a load of several hundred users simultaneously without glitching would need hundreds of testers. Doesn’t look like a logical or economically viable solution, does it?
However, a script can emulate such a load with ease. Automated testing is required for load, stress, and performance tests. However, these tests aren’t necessary for each and every app you develop. You’ll need to decide whether to perform them for each product separately.
3. Shortcomings of automated testing
3.1. Automated testing is more complex than manual testing
Scripts don’t write themselves. QAs write them manually for each task, and this means a QA automation engineer needs programming skills and knowledge of at least one programming language (the most popular for automated testing being Python, Java, and C#). To set up automated testing, a QA compiles a test scenario for a script to run. Each scenario is handwritten, which takes time on the part of a QA.
Still, with repetitive tasks and tasks that can be automated, in the long run, automation is the better option.
3.2. Automated tests aren’t the answer to all issues
There are things automated tests can’t do with current technologies. For example, they can’t replace manual tests when it comes to testing design or user-friendliness — these things require human insights. However, tests of an app’s design and user-friendliness aren’t always performed by QAs either: user feedback can be acquired from a test group of users in addition to company employees. This test group may or may not be paid.
Another case where automated testing falls short is the testing of completely new functionality. For a QA specialist to know how to program a test script, they need to know what results they should expect.
Most software tests can be automated. But not all. There are still cases where manual testing is the preferred method. Let’s talk a little about the advantages of manual testing over automated testing.
4. Benefits of manual testing
The reality of modern software development is that most tests are still performed manually. The reasons vary from one company to another. We’ll highlight just some of them here.
4.1. Manual testing is easier to implement
It’s fairly simple to equip your company with qualified manual QA specialists as opposed to automation experts. Many manual testing tasks can be done with no access to code and no knowledge of coding. That’s why testing is sometimes considered the entryway into software development — you can start with the bare minimum of knowledge and gain skills along the way. This means there are more good manual QAs on the market than there are automation specialists.
4.2. Manual testing is the right choice for extremely complex tasks
When testing exceptionally complex features, the time to run manual tests and the cost of doing so can sometimes be less than the time and money necessary to write automation scripts. Besides, these kinds of tasks are usually only completed once due to their specifics. This makes automation cost-inefficient.
However, this will also depend at least in part on your QA’s skills, as a highly qualified automation specialist is able to create complex scenarios faster and with more precision than a junior QA. You’ll also need to calculate the usefulness of creating each automation script.
4.3. Manual testing is more suitable for certain tasks
Interface design, user experience, and usability still cannot be tested by scripts. These tests require human feedback — sometimes from quality assurance specialists, other times from a test group of users.
Another case is when extra attention must be paid to specific parts of a test — writing a script for such a test is too complicated and usually not as reliable as using a specialist who knows what to look for.
Sometimes, QAs also perform tests spontaneously, in an unusual way, and without preparation. This is called ad-hoc testing. Ad-hoc testing can help you find unexpected flaws. For such tests, writing a script is impossible since you don’t know what outcome to expect. Besides, such scripts would probably only be used once.
Example: One type of ad-hoc testing, called monkey testing, aims to find out what needs to be done to break the system. Random actions are performed to see if anything triggers the system to crash.
5. Shortcomings of manual testing
Here’s why automation testing is now often preferred over manual testing.
5.1. Manual testing is inherently slower
The same task that might take a human QA several hours or even days to complete will take mere minutes or even seconds for a machine. Computerized systems and scripts analyze data faster than a human. Manual testing is tedious and time-consuming, especially with repetitive tasks, while test automation conducted with proper preparation is swift and simple.
5.2. Manual testing is prone to errors
People can miss details when it comes to tasks that are run over and over, like retesting a feature after each update.
Distributing attention over multiple points in a single task can also spell trouble for a QA, making test results less reliable. With complex features, you’ll need to decide between manual and automated testing on a case-by-case basis. Sometimes, automation can be irrationally costly and time-consuming due to the complexity of scripts, especially if a test is only run once.
5.3. In the long run, having only manual testing can be more expensive
It’s true that with automated testing a company needs to invest a sometimes considerable sum from the get-go, both on software and to hire qualified personnel (automation QAs cost more than manual specialists).
However, depending on the type and number of tests required for the project, manual testing can also be a financial burden. When a project is big and tests take a lot of time to complete or are repeated multiple times, the cost skyrockets. This issue should be addressed at the beginning of project planning to evaluate the cost of both options and find out which is most economically feasible. Usually, the best decision is to combine manual and automated testing.
6. Manual testing vs automated testing — the showdown
Now let’s see a side-by-side comparison of manual testing vs automated testing.
|Manual testing||Automated testing|
Takes a lot of time to complete
Takes way less time to complete
Does not require programming skills
Requires programming skills
Lower initial cost but the longer the tests are run, the higher the cost
Requires higher initial investment but is more profitable for long-term projects with a lot of repetitive tests
Higher possibility of errors due to the human factor
More precise and reliable if tests are well built
Complex tasks require additional specialists
Complex tasks require additional preparation time
Isn’t suitable for performance, load, or stress testing
Isn’t suitable for usability, user interface, or user experience testing
7. Where should you use manual testing?
Here are some tests that are better run manually:
Exploratory testing. This is initial testing of completely new features. Since the functionality involved is new and no ready-made test cases are available, automating this kind of test is impossible.
Visual GUI and usability testing. Testing user interfaces and user experiences includes a visual evaluation and requires human observation.
Ad-hoc testing. These are spontaneous tests done without adhering to requirements or documentation and aimed at unveiling unexpected bugs.
8. Where should you use automated testing?
Test automation is used more and more today, and new cases appear that automated testing can handle. Here are just some examples of where automated testing is recommended:
Smoke testing checks core functionality. It’s usually somewhat standardized and reusable.
Regression testing retests existing functionality after updates to either the application itself or the operating system and is designed to find out whether any conflicts occur.
Performance/load testing is used to test applications intended for heavy use by numerous users at the same time. Load testing simulates a high load to see if the application crashes.
Stress testing is similar to load testing and entails creating a virtual load on the application. However, while load testing is performed to see if the app is able to withstand a specific load, stress testing aims to find out where the limit of the load lies. In other words, it gets the app to the breaking point.
Repeated execution. Some tests are run repeatedly at certain points of development or are standard tests reusable for different applications.
After comparing manual and automated testing, we can’t say with any certainty whether automated testing is better than manual testing.
Software testing is a complex and greatly varied process. Depending on what’s being tested, at which stage, and for what purpose, different tests will be carried out. And this, of course, affects the choice between manual and automated testing. Some tests are better off automated and others should still be conducted manually.
The best way for software development companies to up their skills is to combine manual and automated testing specialists, divide test tasks between them wisely, and make the best of both methods. Each project can combine manual and automated testing in different proportions, and it’s best to create a project’s testing strategy from the start.