Software Testing Methodologies Explained

Just like software development, software testing is done through a variety of specific methodologies that combine various concepts and ideas to help facilitate the process. Of course, with so many different types of software testing methodologies to choose from, it’s sometimes a challenge to make sure you’ve selected the right one.

 An overview of software testing models:

1.     Waterfall Model (Linear Sequential Life Cycle Model)

One of the oldest methods that can be used, the Waterfall Model, aims to follow a sequence of steps, only allowing the tester to move forward to the next phase of testing after the previous step has been successfully completed.

Waterfall’s advantages lie in its simplicity of use. However, should problems or bugs be discovered during the testing process, it should result in changes being made to the software. Returning to the previous step (i.e. development) is prohibited in this methodology.

2.     V-Model (Verification and Validation model)

The V-Model is also based on a sequential flow of steps. Unlike the Waterfall methodology, testing is done in parallel with development.

According to this testing methodology, “static testing” is done right at the beginning of the process when requirements are ready. This “verification and validation” helps to prevent defects arising later. Test plans are then created for every single one of the software development phases, and usually follow the steps below:

·        The requirements phase of development is done with the acceptance testing 

·        System testing is then done in the high-level design phase 

·        As the design into the “detailed phase”, integration testing is conducted alongside

·        Unit testing of the individual parts is done after the coding stage of development.

Unfortunately, V-Model doesn’t provide clear solutions to eliminate any software defects should they be found in testing.

3.     Incremental Model

This methodology is a bit like the waterfall model of software testing on steroids, as each iteration is divided into even further numbers of cycles, and those cycles divided into even smaller modules.

As per most models, each iteration adds further functionality to the software. An increment in the Incremental Model includes three cycles, which involve:

                   i.           Software designing and realization,

                  ii.           Testing, and

                iii.           Implementation.

The major advantage of the Incremental Model is that it allows for the development of different product versions simultaneously, with each version being one phase behind the first until the project is finished. With such intense testing going on throughout the product life cycle, it’s obvious that this method is targeted at finding errors as fast as possible.

Compared to other methodologies, the Incremental Model is more flexible. It is cheaper to change requirements because it’s easier to debug if you use smaller iterations.

4.     Spiral Model

The Spiral Model is also based on an incremental approach but it makes use of prototypes as well. It consists of four phases:

                   i.           planning,

                  ii.           risk analysis,

                iii.           engineering, and

                iv.           Evaluation.

Although the spiral method is quite old, it remains useful both for testing and software development due to its cyclical nature: the first cycle starts in planning, then the second starts, and so on until the evaluation phase.

The main advantage of this methodology is the test feedback available at the third stage of each cycle, which helps to guarantee the quality of the evaluation.

5.     Agile Model

Interactive, dynamic and true to its name, agile software development and testing is reliant on teams self-organising and ensuring the implementation of revisions in response to requirement changes.

Working in short sprints (or iterations) agile software development methodologies, therefore, minimise risk by developing information in short timeboxes that can be assessed at regular scrum meetings. This approach allows teams to stay flexible. It facilitates quick response to any possible requirement changes that may arise, rather than being bound by long-term planning and extended development.

6.     Extreme Programming (XP)

A flexible software development methodology, a distinctive feature of Extreme Programming, is “pair programming” where one developer works with the code while a software tester reviews the newly written code in parallel.

Importantly, the test determines the code, which means a piece of code can only be considered as complete if all the tests are passed successfully. Otherwise, it will be rejected. As part of this process, every application module should have a unit test to ensure that errors are identified and fixed as part of that phase of coding.

The constant, ongoing testing and small releases ensure the high quality of the code and present the major advantages of such a methodology. Defect documentation, however, is not always high level, so this lack of software quality can present problems in the future.

7.     Scrum

Perhaps the most well-known Agile methodology, Scrum, is an iterative and incremental framework using short sprints or timeboxes for release planning and the management of software application development.

Highly collaborative with both the customer and the product owner, the Scrum QA team must be present at all daily scrum meetings to:

·        Define acceptance criteria,

·        Share with the team at large what was tested the day before,

·        What will be tested today, and

·        How the overall software and automation testing is progressing.

It’s worth bearing in mind that the principles of Scrum’s agile methodology can cause testing challenges due to the often-changing product requirements, which means the tester must stay involved and up to date with latest developments all the time.

The right method for you?

In today’s day and age, the decision regarding which software testing methodology to choose depends on many different factors, such as:

·        The type of project,

·        Requirements, and

·        Project schedule.

There’s no such thing as one methodology that is suitable for all types of projects.

From a software testing point of view, the decision as to which route is best to take is also often influenced by budget and time constraints, as some methods are focused on providing testing input early in the development lifecycle, while others prefer to wait until later when a working model or prototype of the system is ready.

It’s also important to remember that the goal of many software test methodologies has changed recently. No longer simply intended for finding defects in applications, testing methodologies are now also used for figuring out exactly what causes bugs. Working collaboratively with developers in this way, therefore, ensures a more efficient way of work and the quick eradication of errors.

Based in Cape Town, South Africa, our Global Testing Centre provides managed outsourced services for software testing to clients around the globe. So, if you want to turn an idea into a software product fast and need the quality assurance that should go along with it, then contact us today to find out how we can help you.

FAQ's we regularly come up in this space:

Q1: What is software testing methodology?

A1: Standard development methodologies describe a set of general testing mechanisms which must be incorporated in the product development lifecycle. These mechanisms start from testing very small of code piece by piece to testing the whole application functionality in the end.

- Unit Tests

This is the most basic testing mechanism at the developer level. This covers very narrow and well defined scope. We isolate the code from any outside interaction or any dependency on any module.

- Integration Tests

Integration Test forms the next class of tests at the developer level. They provide a mechanism to test the interoperation of smaller units. Integration test involve testing the modules which access network, databases and file systems.  

- Functional Tests

After the integration tests are performed, higher level tests are used. Functional tests check for the correctness of the output with respect to the input defined in the specification. Not much emphasis is given on the intermediate values but more focus is given on the final output delivered.

- Smoke Tests

Smoke Tests analogy comes from the electronics where a mistake means the circuit board giving out smoke. After functional tests are done a simple test is done from the start typically after a fresh installation and newer input values. Luckily there is no smoke in software industry but yeah, crashes are there to indicate trouble.

- Regression Tests

Whenever complex bugs are patched in a system, typically which affect the core areas of the system, regression tests are used to re test all the modules of the system.

- Acceptance Tests

These form the final level of test plan. Every feature is checked from the user’s perspective by the testing team and the feature is marked accepted or rejected. These tests test the application from end user’s perspective like detecting crashes after going through a certain flow.

Q2:  What is software testing approach?

A2: Implementation of test strategy for a particular project is known as "test approach". The test approach is usually defined in all test plans and test designs. Test approach refers to the commencement of various project activities such as planning the testing process, selecting the designs, defining the entry and exit criteria etc.

There are two approaches in testing:

Preventative approach.

Reactive approach.

In preventative approach, tests are designed at an early stage, i.e. before the commencement of software development.

In Reactive approach, tests are designed after software development.

Before selecting a 'test approach', we should consider the following factors:

Analyse the various risks associated with failure of the project - to the people,the environment, and the company.

Analyse the expertise and efficiency of the people in the proposed tools and techniques.

The nature of product and the business.

Q3: How to choose a software testing methodology?

A3: Testing technique refers to the method or way to test a software or a part of software. Each testing technique has its own benefits. Different techniques target different types of defects. So, it would be wrong to call one technique best. Based on the software and its requirements, one test technique may suit better than the other to serve the purpose. And sometimes, a combination of different testing technique might be a good way to test a software.

The various factors that determine which testing technique should be used:

Time constraint – It helps in eliminating and/or selecting testing types, depending on the timeline allotted for testing. For ex, a software with a small timeline for testing will more likely skip Endurance Testing.

Budget – Budget might put a restraint on the different aspects of testing which may impact the choice of testing technique.

Specifications provided by Client – Sometimes client can provide clear guidelines as to what testing needs to be done. They can also intervene to eliminate the testing types identified during planning too.

Q4: When software testing should start?

A4: It has been observed that most of the errors are identified in the testing phase which is already introduced in the requirement or design phase. Defects identified later in SDLC are expensive to fix than defects identified in early stage. So testing should start early to avoid the introduction of defects in the early phase.

So start testing early in the software development would solve the problem, as the earlier you find a bug, the cheaper it is to fix it.

In the requirement phase if we found issue or conflict in the requirements itself then it won’t take to much time to fix the issue. But if bug found in early stage of SDLC then to fix this bug would take 50 times cheaper than fixing bug in actual testing. It would be more costly if bug is found in maintenance phase means after going to product live.

Q5: When to end software testing?

A5: During the software development process, there are various questions on which management have to take decision. One such crucial question is deciding onto the release policies and the optimal time to stop software testing. In order to decide software release time, management is dependent upon its testing team which is responsible for finding bugs in the software and their removal before the software is unveiled in the market. Hence testing can prove to be corrective as well as innovative phase of a software lifecycle. Bugs that are found during the testing phase can be used as ideas for feature enhancement.

Bugs found in the earlier stages of the development reduce the cost of production. Hence it is very important to find the errors as early as possible. Early release of a software can result in uncovered faults which might cost heavily on the vendor. On the other hand, a late release leads to consumption of more resources and hence increase the production cost. Moreover, late release might end up in the loss of market opportunities. Hence, both, economic factors and technical factors have to be taken care of while deciding the optimal release time of the software product.