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The Beginner’s Guide to Software Testing: Basics, Types, and Methodologies

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If you’ve ever assembled furniture by yourself, you probably know how important it is to actually test what you’ve created before using it - after all, you’d probably prefer to discover a bolt or screw to be loose during a checkup, instead of having a book-filled shelf fall on somebody’s head.

This is exactly what software testing is to software development - you want to make sure every part of your app/system/framework/whatever works as intended before having it published. After all, you’d rather find out any coding mistakes and incompatibilities before delivering your software to the end client, wouldn’t you?

Most software development approaches break down projects into segments, or modules, to make the development process more streamlined and easier to actually complete - but who’s to say the modules will still work when connected into a complete system? Finding that out is one of the primary objectives of software testing.

If you’re an aspiring software engineer, knowing how to go about software testing is a must - while a fun passion project might not need extensive testing, a commercial project absolutely does. Trust us - it’s nothing pleasant to receive complaints from your clients, because an end user found out an exploit that threatens the security of the whole app.

But what are the exact objectives of software testing? And what is software testing, exactly? What could go wrong if you don’t perform it well enough? What are the approaches to testing, and what are its different types?

To answer these questions, we have prepared this extensive Guide to Software Testing. Let’s dive in!

What is the purpose of Software Testing?

This one might sound self-explanatory at first - the purpose of software testing is to find defects, right?

Well, that is true - to an extent. Finding errors and inconsistencies within the software is one of the major objectives of software testing. During the development process, a lot of things might look like they’re going to work, but reality proves otherwise - testing gives you the opportunity to detect these flaws, which gives you valuable information when trying to fix those defects.

That’s the second aim of software testing - to provide you with information about the quality of your software, necessary for removing defects and fixing errors. Imagine bug fixing without testing - having to look through the entire code, guessing what works and what doesn’t. That’s an easy way to end up in an insane asylum!

When working on commercial projects, your software will have to meet specific business and user requirements. Testing lets you verify whether you are actually meeting those requirements, and whether the software is ready for delivery or still needs some touch-ups.

Is Software Testing really necessary? The benefits of Software Testing

If there is one thing that’s impossible to rule out during the software development life cycle, it’s the human error. They can be tiny or they can be catastrophic, but you can be almost certain some defects will show up in the code. Some of them might be pretty much impossible to find out without rigorous testing, which is exactly what makes software testing so important.

When trying to make a name for yourself or your brand, you want your clients to think highly of you - that will not happen if you keep delivering a faulty product. Just like Quality Assurance is necessary in manufacturing to ensure high quality of produced goods, software testing is unavoidable if you want your software to be top-notch.

Software testing is a huge contributor to the overall success of the app or system you’re working on. Without testing, the process of fixing defects can be long and expensive. It’s often best to begin testing as soon as possible - you can start involving your testers in the development process right at the requirement review, where they’ll be able to figure out possible defects in the requirements themselves, saving you time during implementation.

Testing isn’t something that you should start worrying about only after you’re finished with developing given software - in fact, the most successful IT companies keep testers involved in the development process from the start. As they work together with software engineers and system designers, testers gain a better understanding of the inner workings of your software. What’s more, they help reduce the number of serious design flaws, allowing you to properly identify and deal with defects at the earliest stages of development.

The more closely your testers are involved in the development process, the fewer bugs you’ll have to fix before the release. The software testing phase itself, which usually comes late in the development, can be significantly shortened by involving your testers early on. Not only do the testers gain the developers’ insight, but the developers also gain the testers’ insight. This helps them take care of potential defects and failures on the go, without having to go through arduous error management.

Software Testing methodologies: Agile, Waterfall, or V-Model?

Now that you know what software testing is and why it’s so important within the software development framework, we can dive in deeper and talk about different approaches to software testing. There is no single way of handling testing - different teams and different project types can benefit from different approaches. Depending on what you’re working on and who you’re working with, you should be able to pick the methodology that will promote quality and timely delivery.

But what are those methodologies? While we probably don’t have the space to describe them all right here, let’s talk about the three most common: Agile, Waterfall, and V-Model.

Agile - fast, flexible, and proven

If continuous testing and DevOps feel like a perfect description of your software development life cycle, Agile methodology might be the perfect one for you. In Agile testing, you don’t wait for the development to finish before testing begins - if you’re familiar with the iterative specificity of the Agile framework, you’ve probably guessed that testing is done at every iteration - and as much of it as possible!

In Agile, testers, developers, and designers work very closely together - teamwork and proper communication are a must. One of the core tenets of Agile development is continuous testing - the importance of testing in Agile is so vast that some teams even decide to practice TDD, or Test-Driven Development. In TDD, tests are written first, designed to check an aspect of the program that hasn’t been created yet. Of course, such a test will immediately fail - which is exactly the point! Only then will developers start writing the code, specifically to pass the test written beforehand.

In summary, let’s go over the upsides and downsides of Agile testing:

Great for projects of all sizes

✓ Helps keeping a stable delivery schedule
✓ Easy implementation of requirement changes
✓ Centered on customer satisfaction

𐄂 Less predictable than other methodologies
𐄂 Requires very good communication and teamwork
𐄂 Less detailed documentation, making it difficult to introduce new members to an ongoing project

Waterfall - separate, well-documented, solid

Agile testing is great, allowing for minimal planning and little documentation, while often providing amazing results.

However, Agile has its shortcomings. How do you introduce Agile in a team that’s used to working separately, when a tight schedule prevents you from starting with lengthy team-building workshops? Or what if a senior tester suddenly decides to leave and there’s nobody to replace him - after all, with Agile’s barebones documentation, it might take some time for a new tester to get up to speed.

Waterfall can be a great alternative when Agile doesn’t seem to work very well. While much less flexible than Agile, it might provide better results in projects that are well-defined from the get-go and have very precise client requirements that you know won’t change.

In contrast to Agile, Waterfall methodology treats testing as a separate phase, rather than having it performed along the development phase. Testing starts after the development is finished, and the two teams work mostly separately from each other. The entire process follows a linear path - it’s simple to understand and training your employees to follow it won’t be time-consuming and expensive.

How does it perform compared to Agile? That depends - let’s take a look at Waterfall’s advantages and disadvantages.

✓ Works well with small projects
✓ No need for continuous communication and strict teamwork
✓ Easy to manage
✓ Well-defined structure and very detailed documentation...

𐄂 much documentation. Really. Tons.
𐄂 Doesn’t adapt very well to requirement changes
𐄂 Gets outperformed by Agile in large-scale projects

V-Model - disciplined and productive, but also iterative

While Waterfall certainly has its applications, we can often see it as quite rigid when compared to Agile. What if you don’t want the sprint-oriented approach that Agile introduces, but you also don’t want to wait with testing until the very end of development like in Waterfall? Enter V-Model.

V-Model, or Verification and Validation Model, is an extension of the Waterfall framework - however, it breaks down testing into individual phases. Each stage of software development has its own testing stage, helping testers find issues earlier. Most often, there will be four testing stages:

  1. Unit Testing
  2. Integration Testing
  3. System Testing
  4. Acceptance Testing

V-Model is a great approach if you’re feeling comfortable in well-structured and systematic frameworks, but don’t want to pile work at the very end of your SDLC (Software Development Life Cycle). It allows you to avoid the downward flow of defects, which is a common problem with the Waterfall framework - but still allows limited communication between testers and developers, which is especially useful if you’re outsourcing.

Let’s go over some of the pros and cons of the V-Model approach:

✓ Simple and easy to learn structure
✓ Test planning and test design happens before coding
✓ Defects can be found at early stages
✓ Works wonders for small, well-defined projects

𐄂 Very poor flexibility
𐄂 No room for prototyping
𐄂 Risk management might be more difficult than in other approaches

All in all, it’s hard to say which approach is the correct, or better one. Depending on the type of project you’re working on and all the details, you should choose an approach accordingly. Small and rigid projects will benefit from a Waterfall or V-Model approach, while large projects with a high risk of requirement change will definitely do better in Agile.

Functional Testing vs. Non-functional Testing

Now that you know how to approach testing, let’s take a look at the testing process itself. The first distinction we need to cover is the difference between Functional Testing and Non-functional Testing. Most projects will require both functional tests and non-functional tests to achieve satisfactory results, which makes these two concepts very important to differentiate for a software tester.

Let’s start with Functional Testing. Some might say that functional testing is more important than non-functional testing, as it verifies the software on the basis of the requirement specification. Functional testing focuses on functions and features of your software and might involve checking the UI, various APIs, databases, and security.

Functional testing can be performed both manually and automatically. Automated tests effectively shorten the whole testing phase, allowing your testers to only test manually what can’t be tested automatically. Some areas even require automated testing, as they can’t be easily performed manually - like most non-functional tests.

In contrast to checking functionality, non-functional tests check overall Quality. Non-functional testing is usually extremely hard to perform by yourself, which is why tools like JMeter or Loadster exist, used to automate load testing and stress testing. Non-functional tests cover, as you might have guessed, non-functional aspects, or simply aspects that wouldn’t be covered in requirement specification. These most often include performance, reliability, usability, and so on.

Examples of Functional Testing

To give you a better idea of what Functional Testing is all about, let’s go over some most popular types of functional testing. We’ve chosen Unit Testing, Smoke Testing, System Testing, and Acceptance Testing, but there are dozens of other types of testing, so don’t limit yourself to just these!

Unit Testing

Unit Testing is often the first of the functional tests within a single testing phase. Instead of checking the entire software for defects and failures, the source code is divided into smaller units. These units can be most often tested using automated tests to see whether they meet their design and behave in accordance with requirements.

While Unit Testing is great for testing modules in isolation, its scope is very limited. It won’t catch any integration errors or system errors, exactly because the units are tested in isolation.

Smoke Testing

In software development, simple defects can often ruin entire projects, preventing you from a timely release. To avoid that, Smoke Testing is run to reveal such issues. Smoke tests will help you determine whether your primary functions are working as they should, or whether they’re so broken that further testing will be unnecessary at the moment.

Smoke testing helps save time and is often considered “the most cost-effective method for identifying and fixing defects” - or so at least says Microsoft.

System Testing

Once all the modules are confirmed to work independently, System Testing can verify whether they properly work together in unison. Individual units are compiled into an integrated software, which is then checked against the requirements. System tests help assess interoperability and promote enjoyable user experience.

System testing is a rather broad term, including a variety of testing subtypes. One of the subtypes definitely worth mentioning is End-to-end Testing, which allows developers to verify the functionality of end-user behavior. Such a test replicates many various user scenarios, like adding a product to the cart or creating an account. Unlike many other types of functional testing, E2E testing can be automated to quickly get through large numbers of test cases. Automation is often a necessity in testing, as performing every single test manually would take ages. Before system testing, developers often conduct Integration Testing, which is a step between Unit Testing and System Testing - it groups modules into groups, checking whether there are no incompatibilities between them and whether they communicate without issues.

Acceptance Testing

Acceptance Tests are often among the final tests performed on software, and their aim is to verify whether the final product satisfies all of the formal requirements. A passing acceptance test means that your software is ready to be delivered. Very often in acceptance testing, you’re setting up the criteria for the test from the perspective of an end user.

Examples of Non-Functional Testing

Now, let’s move on to non-functional testing. While these technically aren’t necessary to check whether your software meets requirement specification, they can tell you a lot about the quality of your system. We’ve selected Performance Testing, Load Testing, and Stress Testing, as they are some of the most commonly performed non-functional tests.

Performance Testing

By measuring response times and finding out bottlenecks in your system, Performance Testing gives you valuable insight into how well your software works. They help you validate how fast the software works for end users, and how reliable it is. Performance tests are vital if you care about the quality of your software.

Load Testing

While your software might work perfectly under regular conditions, who knows how it’ll behave under a lot of traffic. Load tests can help you achieve a stable and scalable software by giving you information about at what load point exactly does the performance begin to degrade.

Performing such a test manually would be incredibly difficult, as you would need massive amounts of testers at a single moment. That’s exactly why automated testing exists - to combat these shortcomings and help you better prepare your software for the end client.

Stress Testing

Finally, Stress Testing takes your software to abnormal levels of use - as in simulating a situation where your software is used to a larger extent than previously thought as the limit. This is very important in determining when the software breaks, how the failure is displayed to the end user, and how the system recovers.

Without stress testing, you are left clueless as to what happens when your software breaks - and that’s a genuine possibility that you can’t forget about!


Whew, now that was a lengthy one! We hope you’ve been able to expand your knowledge about software testing with this guide. Now that you know what software testing is, what are the approaches to software testing, as well as some of the common testing types, you pretty much got the hang of the basics.

However, that’s just the basics! Software testing is a massive field with tons of peculiarities and new advancements being brought up almost daily. If you want to become better at software testing, we recommend first and foremost to stay relevant - read the latest articles, follow threads on popular forums, and keep in touch with related social media channels.

If you’ve made it to the end of this article, we’re extremely grateful - you’re the inspiration that keeps us going! We wish you the best of luck on your journey with software testing. For more informative articles, we invite you to check out our blog, where we frequently post the latest news from the software development world, as well as various guides, tutorials, and explanations!

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