Testing is the process of evaluating a system or its component(s) with the intent to find whether it satisfies the specified requirements or not.
Testing is executing a system in order to identify any gaps, errors, or missing requirements is contrary to the actual requirements.
This tutorial will give you a basic understanding of software testing, its types, methods, levels, and other related terminologies.
Testing is the process of evaluating a system or its component(s) with the intent to find whether it satisfies the specified requirements or not. In simple words, testing is executing a system in order to identify any gaps, errors, or missing requirements is contrary to the actual requirements.
According to ANSI/IEEE 1059 standard, Testing can be defined as - A process of analyzing a software item to detect the differences between existing and required conditions (that is defects/errors/bugs) and to evaluate the features of the software item.
Who does Testing?
It depends on the process and the associated stakeholders of the project(s). In the IT industry, large companies have a team with responsibilities to evaluate the developed software in the context of the given requirements. Moreover, developers also conduct testing which is called Unit Testing. In most cases, the following professionals are involved in testing a system within their respective capacities:
- Software Tester
- Software Developer
- Project Lead/Manager
- End User
Different companies have different designations for people who test the software on the basis of their experience and knowledge such as Software Tester, Software Quality Assurance Engineer, QA Analyst, etc.
It is not possible to test the software at any time during its cycle. The next two sections state when testing should be started and when to end it during the SDLC.
When to Start Testing?
An early start to testing reduces the cost and time to rework and produce error-free software that is delivered to the client. However, in the Software Development Life Cycle (SDLC), testing can be started from the Requirements Gathering phase and continued until the deployment of the software. It also depends on the development model that is being used. For example, in the Waterfall model, formal testing is conducted in the testing phase; but in the incremental model, testing is performed at the end of every increment/iteration and the whole application is tested at the end.
Testing is done in different forms at every phase of SDLC:
- During the requirement gathering phase, the analysis and verification of requirements are also considered as testing.
- Reviewing the design in the design phase with the intent to improve the design is also considered as testing.
- Testing performed by a developer on completion of the code is also categorized as testing.
When to Stop Testing?
It is difficult to determine when to stop testing, as testing is a never-ending process and no one can claim that a software is 100% tested. The following aspects are to be considered for stopping the testing process:
- Testing Deadlines
- Completion of test case execution
- Completion of functional and code coverage to a certain point
- Bug rate falls below a certain level and no high-priority bugs are identified
- Management decision
Verification & Validation
These two terms are very confusing for most people, who use them interchangeably. The following table highlights the differences between verification and validation.
| S.N. | Verification | Validation |
|---|---|---|
| 1 | Verification addresses the concern: "Are you building it right?" | Validation addresses the concern: "Are you building the right thing?" |
| 2 | Ensures that the software system meets all the functionality. | Ensures that the functionalities meet the intended behavior. |
| 3 | Verification takes place first and includes the checking for documentation, code, etc. | Validation occurs after verification and mainly involves the checking of the overall product. |
| 4 | Done by developers. | Done by testers. |
| 5 | It has static activities, as it includes collecting reviews, walkthroughs, and inspections to verify a software. | It has dynamic activities, as it includes executing the software against the requirements. |
| 6 | It is an objective process and no subjective decision should be needed to verify a software. | It is a subjective process and involves subjective decisions on how well a software works. |
Software Testing - QA, QC & Testing
Most people get confused when it comes to pin down the differences among Quality Assurance, Quality Control, and Testing. Although they are interrelated and to some extent, they can be considered as same activities, but there exist distinguishing points that set them apart. The following table lists the points that differentiate QA, QC, and Testing.
| Quality Assurance | Quality Control | Testing |
|---|---|---|
| QA includes activities that ensure the implementation of processes, procedures and standards in context to verification of developed software and intended requirements. | It includes activities that ensure the verification of a developed software with respect to documented (or not in some cases) requirements. | It includes activities that ensure the identification of bugs/error/defects in a software. |
| Focuses on processes and procedures rather than conducting actual testing on the system. | Focuses on actual testing by executing the software with an aim to identify bug/defect through the implementation of procedures and process. | Focuses on actual testing. |
| Process-oriented activities. | Product-oriented activities. | Product-oriented activities. |
| Preventive activities. | It is a corrective process. | It is a preventive process. |
| It is a subset of Software Test Life Cycle (STLC). | QC can be considered as the subset of Quality Assurance. | Testing is the subset of Quality Control. |
Testing and Debugging
Testing : It involves identifying a bug/error/defect in a software without correcting it. Normally professionals with a quality assurance background are involved in bugs identification. Testing is performed in the testing phase.
Debugging : It involves identifying, isolating, and fixing the problems/bugs. Developers who code the software conduct debugging upon encountering an error in the code. Debugging is a part of White Box Testing or Unit Testing. Debugging can be performed in the development phase while conducting Unit Testing or in phases while fixing the reported bugs.
This section describes the different types of testing that may be used to test a software during SDLC.
Manual Testing
Manual testing includes testing a software manually, i.e., without using any automated tool or any script. In this type, the tester takes over the role of an end-user and tests the software to identify any unexpected behavior or bug. There are different stages for manual testing such as unit testing, integration testing, system testing, and user acceptance testing.
Testers use test plans, test cases, or test scenarios to test a software to ensure the completeness of testing. Manual testing also includes exploratory testing, as testers explore the software to identify errors in it.
Automation Testing
Automation testing, which is also known as Test Automation, is when the tester writes scripts and uses another software to test the product. This process involves automation of a manual process. Automation Testing is used to re-run the test scenarios that were performed manually, quickly, and repeatedly.
Apart from regression testing, automation testing is also used to test the application from load, performance, and stress point of view. It increases the test coverage, improves accuracy, and saves time and money in comparison to manual testing.
What is Automate?
It is not possible to automate everything in a software. The areas at which a user can make transactions such as the login form or registration forms, any area where large number of users can access the software simultaneously should be automated.
Furthermore, all GUI items, connections with databases, field validations, etc. can be efficiently tested by automating the manual process.
When to Automate?
Test Automation should be used by considering the following aspects of a software:
- Large and critical projects
- Projects that require testing the same areas frequently
- Requirements not changing frequently
- Accessing the application for load and performance with many virtual users
- Stable software with respect to manual testing
- Availability of time
How to Automate?
Automation is done by using a supportive computer language like VB scripting and an automated software application. There are many tools available that can be used to write automation scripts. Before mentioning the tools, let us identify the process that can be used to automate the testing process:
- Identifying areas within a software for automation
- Selection of appropriate tool for test automation
- Writing test scripts
- Development of test suits
- Execution of scripts
- Create result reports
- Identify any potential bug or performance issues
Software Testing Tools
The following tools can be used for automation testing:
- HP Quick Test Professional
- Selenium
- IBM Rational Functional Tester
- SilkTest
- TestComplete
- Testing Anywhere
- WinRunner
- LoadRunner
- Visual Studio Test Professional
- WATIR
There are different methods that can be used for software testing. This chapter briefly describes the methods available.
Black-Box Testing
The technique of testing without having any knowledge of the interior workings of the application is called black-box testing. The tester is oblivious to the system architecture and does not have access to the source code. Typically, while performing a black-box test, a tester will interact with the system's user interface by providing inputs and examining outputs without knowing how and where the inputs are worked upon.
The following table lists the advantages and disadvantages of black-box testing.
| Advantages | Disadvantages |
|---|---|
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White-Box Testing
White-box testing is the detailed investigation of internal logic and structure of the code. White-box testing is also called glass testing or open-box testing. In order to perform white-box testing on an application, a tester needs to know the internal workings of the code.
The tester needs to have a look inside the source code and find out which unit/chunk of the code is behaving inappropriately.
The following table lists the advantages and disadvantages of white-box testing.
| Advantages | Disadvantages |
|---|---|
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Grey-Box Testing
Grey-box testing is a technique to test the application with having a limited knowledge of the internal workings of an application. In software testing, the phrase the more you know, the better carries a lot of weight while testing an application.
Mastering the domain of a system always gives the tester an edge over someone with limited domain knowledge. Unlike black-box testing, where the tester only tests the application's user interface; in grey-box testing, the tester has access to design documents and the database. Having this knowledge, a tester can prepare better test data and test scenarios while making a test plan.
| Advantages | Disadvantages |
|---|---|
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A Comparison of Testing Methods
The following table lists the points that differentiate black-box testing, grey-box testing, and white-box testing.
| Black-Box Testing | Grey-Box Testing | White-Box Testing |
|---|---|---|
| The internal workings of an application need not be known. | The tester has limited knowledge of the internal workings of the application. | Tester has full knowledge of the internal workings of the application. |
| Also known as closed-box testing, data-driven testing, or functional testing. | Also known as translucent testing, as the tester has limited knowledge of the insides of the application. | Also known as clear-box testing, structural testing, or code-based testing. |
| Performed by end-users and also by testers and developers. | Performed by end-users and also by testers and developers. | Normally done by testers and developers. |
| Testing is based on external expectations - Internal behavior of the application is unknown. | Testing is done on the basis of high-level database diagrams and data flow diagrams. | Internal workings are fully known and the tester can design test data accordingly. |
| It is exhaustive and the least time-consuming. | Partly time-consuming and exhaustive. | The most exhaustive and time-consuming type of testing. |
| Not suited for algorithm testing. | Not suited for algorithm testing. | Suited for algorithm testing. |
| This can only be done by trial-and-error method. | Data domains and internal boundaries can be tested, if known. | Data domains and internal boundaries can be better tested. |
There are different levels during the process of testing. In this chapter, a brief description is provided about these levels.
Levels of testing include different methodologies that can be used while conducting software testing. The main levels of software testing are:
- Functional Testing
- Non-functional Testing
Functional Testing
This is a type of black-box testing that is based on the specifications of the software that is to be tested. The application is tested by providing input and then the results are examined that need to conform to the functionality it was intended for. Functional testing of a software is conducted on a complete, integrated system to evaluate the system's compliance with its specified requirements.
There are five steps that are involved while testing an application for functionality.
| Steps | Description |
|---|---|
| I | The determination of the functionality that the intended application is meant to perform. |
| II | The creation of test data based on the specifications of the application. |
| III | The output based on the test data and the specifications of the application. |
| IV | The writing of test scenarios and the execution of test cases. |
| V | The comparison of actual and expected results based on the executed test cases. |
An effective testing practice will see the above steps applied to the testing policies of every organization and hence it will make sure that the organization maintains the strictest of standards when it comes to software quality.
Unit Testing
This type of testing is performed by developers before the setup is handed over to the testing team to formally execute the test cases. Unit testing is performed by the respective developers on the individual units of source code assigned areas. The developers use test data that is different from the test data of the quality assurance team.
The goal of unit testing is to isolate each part of the program and show that individual parts are correct in terms of requirements and functionality.
Limitations of Unit Testing
Testing cannot catch each and every bug in an application. It is impossible to evaluate every execution path in every software application. The same is the case with unit testing.
There is a limit to the number of scenarios and test data that a developer can use to verify a source code. After having exhausted all the options, there is no choice but to stop unit testing and merge the code segment with other units.
Integration Testing
Integration testing is defined as the testing of combined parts of an application to determine if they function correctly. Integration testing can be done in two ways: Bottom-up integration testing and Top-down integration testing.
| S.N. | Integration Testing Method |
|---|---|
| 1 |
Bottom-up integration
This testing begins with unit testing, followed by tests of progressively higher-level combinations of units called modules or builds.
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| 2 |
Top-down integration
In this testing, the highest-level modules are tested first and progressively, lower-level modules are tested thereafter.
|
In a comprehensive software development environment, bottom-up testing is usually done first, followed by top-down testing. The process concludes with multiple tests of the complete application, preferably in scenarios designed to mimic actual situations.
System Testing
System testing tests the system as a whole. Once all the components are integrated, the application as a whole is tested rigorously to see that it meets the specified Quality Standards. This type of testing is performed by a specialized testing team.
System testing is important because of the following reasons:
- System testing is the first step in the Software Development Life Cycle, where the application is tested as a whole.
- The application is tested thoroughly to verify that it meets the functional and technical specifications.
- The application is tested in an environment that is very close to the production environment where the application will be deployed.
- System testing enables us to test, verify, and validate both the business requirements as well as the application architecture.
Regression Testing
Whenever a change in a software application is made, it is quite possible that other areas within the application have been affected by this change. Regression testing is performed to verify that a fixed bug hasn't resulted in another functionality or business rule violation. The intent of regression testing is to ensure that a change, such as a bug fix should not result in another fault being uncovered in the application.
Regression testing is important because of the following reasons:
- Minimize the gaps in testing when an application with changes made has to be tested.
- Testing the new changes to verify that the changes made did not affect any other area of the application.
- Mitigates risks when regression testing is performed on the application.
- Test coverage is increased without compromising timelines.
- Increase speed to market the product.
Acceptance Testing
This is arguably the most important type of testing, as it is conducted by the Quality Assurance Team who will gauge whether the application meets the intended specifications and satisfies the client’s requirement. The QA team will have a set of pre-written scenarios and test cases that will be used to test the application.
More ideas will be shared about the application and more tests can be performed on it to gauge its accuracy and the reasons why the project was initiated. Acceptance tests are not only intended to point out simple spelling mistakes, cosmetic errors, or interface gaps, but also to point out any bugs in the application that will result in system crashes or major errors in the application.
By performing acceptance tests on an application, the testing team will reduce how the application will perform in production. There are also legal and contractual requirements for acceptance of the system.
Alpha Testing
This test is the first stage of testing and will be performed amongst the teams (developer and QA teams). Unit testing, integration testing and system testing when combined together is known as alpha testing. During this phase, the following aspects will be tested in the application:
- Spelling Mistakes
- Broken Links
- Cloudy Directions
- The Application will be tested on machines with the lowest specification to test loading times and any latency problems.
Beta Testing
This test is performed after alpha testing has been successfully performed. In beta testing, a sample of the intended audience tests the application. Beta testing is also known as pre-release testing. Beta test versions of software are ideally distributed to a wide audience on the Web, partly to give the program a "real-world" test and partly to provide a preview of the next release. In this phase, the audience will be testing the following:
- Users will install, run the application and send their feedback to the project team.
- Typographical errors, confusing application flow, and even crashes.
- Getting the feedback, the project team can fix the problems before releasing the software to the actual users.
- The more issues you fix that solve real user problems, the higher the quality of your application will be.
- Having a higher-quality application when you release it to the general public will increase customer satisfaction.
Non-Functional Testing
This section is based upon testing an application from its non-functional attributes. Non-functional testing involves testing a software from the requirements which are nonfunctional in nature but important such as performance, security, user interface, etc.
Some of the important and commonly used non-functional testing types are discussed below.
Performance Testing
It is mostly used to identify any bottlenecks or performance issues rather than finding bugs in a software. There are different causes that contribute in lowering the performance of a software:
- Network delay
- Client-side processing
- Database transaction processing
- Load balancing between servers
- Data rendering
Performance testing is considered as one of the important and mandatory testing type in terms of the following aspects:
- Speed (i.e. Response Time, data rendering and accessing)
- Capacity
- Stability
- Scalability
Performance testing can be either qualitative or quantitative and can be divided into different sub-types such as Load testing and Stress testing.
Load Testing
It is a process of testing the behavior of a software by applying maximum load in terms of software accessing and manipulating large input data. It can be done at both normal and peak load conditions. This type of testing identifies the maximum capacity of software and its behavior at peak time.
Most of the time, load testing is performed with the help of automated tools such as Load Runner, AppLoader, IBM Rational Performance Tester, Apache JMeter, Silk Performer, Visual Studio Load Test, etc.
Virtual users (VUsers) are defined in the automated testing tool and the script is executed to verify the load testing for the software. The number of users can be increased or decreased concurrently or incrementally based upon the requirements.
Stress Testing
Stress testing includes testing the behavior of a software under abnormal conditions. For example, it may include taking away some resources or applying a load beyond the actual load limit.
The aim of stress testing is to test the software by applying the load to the system and taking over the resources used by the software to identify the breaking point. This testing can be performed by testing different scenarios such as:
- Shutdown or restart of network ports randomly
- Turning the database on or off
- Running different processes that consume resources such as CPU, memory, server, etc.
Usability Testing
Usability testing is a black-box technique and is used to identify any error(s) and improvements in the software by observing the users through their usage and operation.
According to Nielsen, usability can be defined in terms of five factors, i.e. efficiency of use, learn-ability, memory-ability, errors/safety, and satisfaction. According to him, the usability of a product will be good and the system is usable if it possesses the above factors.
Nigel Bevan and Macleod considered that usability is the quality requirement that can be measured as the outcome of interactions with a computer system. This requirement can be fulfilled and the end-user will be satisfied if the intended goals are achieved effectively with the use of proper resources.
Molich in 2000 stated that a user-friendly system should fulfill the following five goals, i.e., easy to Learn, easy to remember, efficient to use, satisfactory to use, and easy to understand.
In addition to the different definitions of usability, there are some standards and quality models and methods that define usability in the form of attributes and sub-attributes such as ISO-9126, ISO-9241-11, ISO-13407, and IEEE std.610.12, etc.
UI vs Usability Testing
UI testing involves testing the Graphical User Interface of the Software. UI testing ensures that the GUI functions according to the requirements and tested in terms of color, alignment, size, and other properties.
On the other hand, usability testing ensures a good and user-friendly GUI that can be easily handled. UI testing can be considered as a sub-part of usability testing.
Security Testing
Security testing involves testing a software in order to identify any flaws and gaps from security and vulnerability point of view. Listed below are the main aspects that security testing should ensure:
- Confidentiality
- Integrity
- Authentication
- Availability
- Authorization
- Non-repudiation
- Software is secure against known and unknown vulnerabilities
- Software data is secure
- Software is according to all security regulations
- Input checking and validation
- SQL insertion attacks
- Injection flaws
- Session management issues
- Cross-site scripting attacks
- Buffer overflows vulnerabilities
- Directory traversal attacks
Portability Testing
Portability testing includes testing a software with the aim to ensure its reusability and that it can be moved from another software as well. Following are the strategies that can be used for portability testing:
- Transferring an installed software from one computer to another.
- Building executable (.exe) to run the software on different platforms.
Portability testing can be considered as one of the sub-parts of system testing, as this testing type includes overall testing of a software with respect to its usage over different environments. Computer hardware, operating systems, and browsers are the major focus of portability testing. Some of the pre-conditions for portability testing are as follows:
- Software should be designed and coded, keeping in mind the portability requirements.
- Unit testing has been performed on the associated components.
- Integration testing has been performed.
- Test environment has been established.
