Software Testing Fundamentals—Concepts, Roles, and Terminology

SOFTWARE TESTING—WHAT, WHY, AND WHO

WHAT IS SOFTWARE TESTING?
Software testing is a process of verifying and validating that a software application or program
1. Meets the business and technical requirements that guided its design and development, and
2. Works as expected.

Software testing also identifies important defects, flaws, or errors in the application code that must be fixed. The modifier “important” in the previous sentence is, well, important because defects must be categorized by severity
(more on this later).

During test planning we decide what an important defect is by reviewing the requirements and design documents with an eye towards answering the question “Important to whom?” Generally speaking, an important defect is one that
from the customer’s perspective affects the usability or functionality of the application. Using colors for a traffic lighting scheme in a desktop dashboard may be a no-brainer during requirements definition and easily implemented during development but in fact may not be entirely workable if during testing we discover that the primary business sponsor is color blind. Suddenly, it becomes an important defect. (About 8% of men and .4% of women have some form of color blindness.)

The quality assurance aspect of software development—documenting the degree to which the developers followed corporate standard processes or best practices—is not addressed in this paper because assuring quality is not a responsibility of the testing team. The testing team cannot improve quality; they can only measure it, although it can be argued that doing things like designing tests before coding begins will improve quality because the coders can then use that information while thinking about their designs and during coding and debugging.

Software testing has three main purposes: verification, validation, and defect finding.
♦ The verification process confirms that the software meets its technical specifications. A “specification” is a description of a function in terms of a measurable output value given a specific input value under specific
preconditions. A simple specification may be along the line of “a SQL query retrieving data for a single account against the multi-month account-summary table must return these eight fields ordered by month within 3 seconds of submission.”
♦ The validation process confirms that the software meets the business requirements. A simple example of abusiness requirement is “After choosing a branch office name, information about the branch’s customer account managers will appear in a new window. The window will present manager identification and summary information about each manager’s customer base: .” Other requirements
provide details on how the data will be summarized, formatted and displayed.
♦ A defect is a variance between the expected and actual result. The defect’s ultimate source may be traced to a fault introduced in the specification, design, or development (coding) phases.

WHY DO SOFTWARE TESTING?

“A clever person solves a problem. A wise person avoids it." - Albert Einstein

Why test software? “To find the bugs!” is the instinctive response and many people, developers and programmers included, think that that’s what debugging during development and code reviews is for, so formal testing is redundant at best. But a “bug” is really a problem in the code; software testing is focused on finding defects in the final product.

Here are some important defects that better testing would have found.
♦ In February 2003 the U.S. Treasury Department mailed 50,000 Social Security checks without a beneficiary name. A spokesperson said that the missing names were due to a software program maintenance error.
♦ In June 1996 the first flight of the European Space Agency's Ariane 5 rocket failed shortly after launching, resulting in an uninsured loss of $500,000,000. The disaster was traced to the lack of exception handling for a floating-point error when a 64-bit integer was converted to a 16-bit signed integer.

Software testing answers questions that development testing and code reviews can’t.
♦ Does it really work as expected?
♦ Does it meet the users’ requirements?
♦ Is it what the users expect?
♦ Do the users like it?
♦ Is it compatible with our other systems?
♦ How does it perform?
♦ How does it scale when more users are added?
♦ Which areas need more work?
♦ Is it ready for release?

What can we do with the answers to these questions?
♦ Save time and money by identifying defects early
♦ Avoid or reduce development downtime
♦ Provide better customer service by building a better application
♦ Know that we’ve satisfied our users’ requirements
♦ Build a list of desired modifications and enhancements for later versions
♦ Identify and catalog reusable modules and components
♦ Identify areas where programmers and developers need training

WHAT DO WE TEST?
First, test what’s important. Focus on the core functionality—the parts that are critical or popular—before looking at the ‘nice to have’ features. Concentrate on the application’s capabilities in common usage situations before going on
to unlikely situations. For example, if the application retrieves data and performance is important, test reasonable queries with a normal load on the server before going on to unlikely ones at peak usage times. It’s worth saying again: focus on what’s important. Good business requirements will tell you what’s important.

The value of software testing is that it goes far beyond testing the underlying code. It also examines the functional behavior of the application. Behavior is a function of the code, but it doesn’t always follow that if the behavior is “bad”
then the code is bad. It’s entirely possible that the code is solid but the requirements were inaccurately or incompletely collected and communicated. It’s entirely possible that the application can be doing exactly what we’re
telling it to do but we’re not telling it to do the right thing.

A comprehensive testing regime examines all components associated with the application. Even more, testing provides an opportunity to validate and verify things like the assumptions that went into the requirements, the appropriateness of the systems that the application is to run on, and the manuals and documentation that accompany the application. More likely though, unless your organization does true “software engineering” (think of Lockheed- Martin, IBM, or SAS Institute) the focus will be on the functionality and reliability of application itself.

Testing can involve some or all of the following factors. The more, the better.
♦ Business requirements
♦ Functional design requirements
♦ Technical design requirements
♦ Regulatory requirements
♦ Programmer code
♦ Systems administration standards and restrictions
♦ Corporate standards
♦ Professional or trade association best practices
♦ Hardware configuration
♦ Cultural issues and language differences

WHO DOES THE TESTING?
Software testing is not a one person job. It takes a team, but the team may be larger or smaller depending on the size and complexity of the application being tested. The programmer(s) who wrote the application should have a reduced role in the testing if possible. The concern here is that they’re already so intimately involved with the product and “know” that it works that they may not be able to take an unbiased look at the results of their labors.

Testers must be cautious, curious, critical but non-judgmental, and good communicators. One part of their job is to ask questions that the developers might find not be able to ask themselves or are awkward, irritating, insulting or even
threatening to the developers.

♦ How well does it work?
♦ What does it mean to you that “it works”?
♦ How do you know it works? What evidence do you have?
♦ In what ways could it seem to work but still have something wrong?
♦ In what ways could it seem to not work but really be working?
♦ What might cause it to not to work well?

A good developer does not necessarily make a good tester and vice versa, but testers and developers do share at least one major trait—they itch to get their hands on the keyboard. As laudable as this may be, being in a hurry to start can cause important design work to be glossed over and so special, subtle situations might be missed that would otherwise be identified in planning. Like code reviews, test design reviews are a good sanity check and well worth the time and effort.

Testers are the only IT people who will use the system as heavily an expert user on the business side. User testing almost invariably recruits too many novice business users because they’re available and the application must be usable by them. The problem is that novices don’t have the business experience that the expert users have and might not recognize that something is wrong. Testers from IT must find the defects that only the expert users will find because the experts may not report problems if they’ve learned that it's not worth their time or trouble.



THE V-MODEL OF SOFTWARE TESTING
Software testing is too important to leave to the end of the project, and the V-Model of testing incorporates testing into the entire software development life cycle. In a diagram of the V-Model, the V proceeds down and then up, from
left to right depicting the basic sequence of development and testing activities. The model highlights the existence of different levels of testing and depicts the way each relates to a different development phase.

Like any model, the V-Model has detractors and arguably has deficiencies and alternatives but it clearly illustrates that testing can and should start at the very beginning of the project. (See Goldsmith for a summary of the pros and cons
and an alternative. Marrik’s articles provide criticism and an alternative.) In the requirements gathering stage the business requirements can verify and validate the business case used to justify the project. The business requirements are also used to guide the user acceptance testing. The model illustrates how each subsequent phase
should verify and validate work done in the previous phase, and how work done during development is used to guide the individual testing phases. This interconnectedness lets us identify important errors, omissions, and other problems before they can do serious harm. Application testing begins with Unit Testing, and in the section titled
“Types of Tests” we will discuss each of these test phases in more detail.



THE TEST PLAN
The test plan is a mandatory document. You can’t test without one. For simple, straight-forward projects the plan doesn’t have to be elaborate but it must address certain items. As identified by the “American National Standards Institute and Institute for Electrical and Electronic Engineers Standard 829/1983 for Software Test Documentation”, the following components should be covered in a software test plan.

Items Covered by a Test Plan :


REDUCE RISK WITH A TEST PLAN
The release of a new application or an upgrade inherently carries a certain amount of risk that it will fail to do what it’s supposed to do. A good test plan goes a long way towards reducing this risk. By identifying areas that are riskier
than others we can concentrate our testing efforts there. These areas include not only the must-have features butalso areas in which the technical staff is less experienced, perhaps such as the real-time loading of a web form’s contents into a database using complex ETL logic. Because riskier areas require more certainty that they work properly, failing to correctly identify those risky areas leads to a misallocated testing effort.

How do we identify risky areas? Ask everyone for their opinion! Gather information from developers, sales and marketing staff, technical writers, customer support people, and of course any users who are available. Historical data and bug and testing reports from similar products or previous releases will identify areas to explore. Bug reports from customers are important, but also look at bugs reported by the developers themselves. These will provide insight to the technical areas they may be having trouble in.

When the problems are inevitably found, it’s important that both the IT side and the business users have previously agreed on how to respond. This includes having a method for rating the importance of defects so that repair work effort can be focused on the most important problems. It is very common to use a set of rating categories that represent decreasing relative severity in terms of business/commercial impact. In one system, '1' is the most severe
and 6' has the least impact. Keep in mind that an ordinal system doesn’t allow an average score to be calculated, but you shouldn’t need to do that anyway—a defect’s category should be pretty obvious.

1. Show Stopper – It is impossible to continue testing because of the severity of the defect.
2. Critical -- Testing can continue but the application cannot be released into production until this defect is fixed.
3. Major -- Testing can continue but this defect will result in a severe departure from the business requirements if released for production.
4. Medium -- Testing can continue and the defect will cause only minimal departure from the business requirements when in production.
5. Minor -– Testing can continue and the defect will not affect the release into production. The defect should be corrected but little or no changes to business requirements are envisaged.
6. Cosmetic -– Minor cosmetic issues like colors, fonts, and pitch size that do not affect testing or production release. If, however, these features are important business requirements then they will receive a higher severity level.

WHAT SHOULD A TEST PLAN TEST?
Testing experts generally agree that test plans are often biased towards functionaltesting during which each feature is tested alone in a unit test, and that the systems integration test is just a series of unit tests strung together. (More on test types later.) The problem that this approach causes is that if we test each feature alone and then string a bunch of these tests together, we might never find that a series of steps such as

{open a document, edit the document, print the document, save the document, edit one page, print one page, save as a new document}

doesn’t work. But a user will find out and probably quickly. Admittedly, testing every combination of keystrokes or commands is difficult at best and may well be impossible (this is where unstructured testing comes in), but we must remember that features don’t function in isolation from each other.

Users have a task orientation. To find the defects that they will find—the ones that are important to them—test plans need to exercise the application across functional areas by mimicking both typical and atypical user tasks. A test like the sequence shown above is called scenario testing, task-based testing, or use-case testing.

An incomplete test plan can result in a failure to check how the application works on different hardware and operating systems or when combined with different third-party software. This is not always needed but you will want to think about the equipment your customers use. There may be more than a few possible system combinations that need to be tested, and that can require a possibly expensive computer lab stocked with hardware and spending much time setting up tests. Configuration testing isn't cheap, but it’s worth it when you discover that the application running on your standard in-house platform which "entirely conforms to industry standards" behaves differently when it runs on the boxes your customers are using. In a 1996 incident this author was involved in, the development and testing was done on new 386-class machines and the application worked just fine. Not until customers complained about performance did we learn that they were using 286’s with slow hard drives.

A crucial test is to see how the application behaves when it’s under a normal load and then under stress. The definition of stress, of course, will be derived from your business requirements, but for a web-enabled application stress could be caused by a spike in the number of transactions, a few very large transactions at the same time, or a large number of almost identical simultaneous transactions. The goal is to see what happens when the application is pushed to substantially more than the basic requirements. Stress testing is often put off until the end of testing, after
everything else that’s going to be fixed has been. Unfortunately that leaves little time for repairs when the requirements specify 40 simultaneous users and you find that performance becomes unacceptable at 50.

Finally, Marick (1997) points out two common omissions in many test plans--the installation procedures and the documentation are ignored. Everyone has tried to follow installation instructions that were missing a key step or two, and we’ve all paged through incomprehensible documentation. Although those documents may have been written by a professional technical writer, they probably weren’t tested by a real user. Bad installation instructions immediately cause lowered expectations of what to expect from the product, and poorly organized or written documentation certainly doesn’t help a confused or irritated customer feel better. Testing installation procedures and documentation is a good way to avoid making a bad first impression or making a bad situation worse.

Test Plan Terminology



TYPES OF SOFTWARE TESTS
The V-Model of testing identifies five software testing phases, each with a certain type of test associated with it.


Each testing phase and each individual test should have specific entry criteria that must be met before testing can begin and specific exit criteria that must be met before the test or phase can be certified as successful. The entry and exit criteria are defined by the Test Coordinators and listed in the Test Plan.

UNIT TESTING
A series of stand-alone tests are conducted during Unit Testing. Each test examinesan individual component that is new or has been modified. A unit test is also called a module test because it tests the individual units of code that
comprise the application.

Each test validates a single module that, based on the technical design documents, was built to perform a certain task with the expectation that it will behave in a specific way or produce specific results. Unit tests focus on functionality
and reliability, and the entry and exit criteria can be the same for each module or specific to a particular module. Unit testing is done in a test environment prior to system integration. If a defect is discovered during a unit test, the severity of the defect will dictate whether or not it will be fixed before the module is approved.

Sample Entry and Exit Criteria for Unit Testing


SYSTEM TESTING
System Testing tests all components and modules that are new, changed, affected by a change, or needed to form the complete application. The system test may require involvement of other systems but this should be minimized as much as possible to reduce the risk of externally-induced problems. Testing the interaction with other parts of the complete system comes in Integration Testing. The emphasis in system testing is validating and verifying the functional design specification and seeing how all the modules work together. For example, the system test for a new web interface that collects user input for addition to a database doesn’t need to include the database’s ETL application—processing can stop when the data is moved to the data staging area if there is one.

The first system test is often a smoke test. This is an informal quick-and-dirty run through of the application’s major functions without bothering with details. The term comes from the hardware testing practice of turning on a new piece of equipment for the first time and considering it a success if it doesn’t start smoking or burst into flame.

System testing requires many test runs because it entails feature by feature validation of behavior using a wide range of both normal and erroneous test inputs and data. The Test Plan is critical here because it contains descriptions of
the test cases, the sequence in which the tests must be executed, and the documentation needed to be collected in each run.

When an error or defect is discovered, previously executed system tests must be rerun after the repair is made to make sure that the modifications didn’t cause other problems. This will be covered in more detail in the section on
regression testing.

Sample Entry and Exit Criteria for System Testing


SYSTEM TESTING
System Testing tests all components and modules that are new, changed, affected by a change, or needed to form the complete application. The system test may require involvement of other systems but this should be minimized as much as possible to reduce the risk of externally-induced problems. Testing the interaction with other parts of the complete system comes in Integration Testing. The emphasis in system testing is validating and verifying the functional design specification and seeing how all the modules work together. For example, the system test for a new web interface that collects user input for addition to a database doesn’t need to include the database’s ETL application—processing can stop when the data is moved to the data staging area if there is one.

The first system test is often a smoke test. This is an informal quick-and-dirty run through of the application’s major functions without bothering with details. The term comes from the hardware testing practice of turning on a new piece of equipment for the first time and considering it a success if it doesn’t start smoking or burst into flame.

System testing requires many test runs because it entails feature by feature validation of behavior using a wide range of both normal and erroneous test inputs and data. The Test Plan is critical here because it contains descriptions of
the test cases, the sequence in which the tests must be executed, and the documentation needed to be collected in each run.

When an error or defect is discovered, previously executed system tests must be rerun after the repair is made to make sure that the modifications didn’t cause other problems. This will be covered in more detail in the section on regression testing.

Sample Entry and Exit Criteria for System Testing



As part of system testing, conformance tests and reviews can be run to verify that the application conforms to corporate or industry standards in terms of portability, interoperability, and compliance with standards. For example,
to enhance application portability a corporate standard may be that SQL queries must be written so that they work against both Oracle and DB2 databases.

INTEGRATION TESTING
Integration testing examines all the components and modules that are new, changed, affected by a change, or needed to form a complete system. Where system testing tries to minimize outside factors, integration testing requires involvement of other systems and interfaces with other applications, including those owned by an outside
vendor, external partners, or the customer. For example, integration testing for a new web interface that collects user input for addition to a database must include the database’s ETL application even if the database is hosted by a vendor—the complete system must be tested end-to-end. In this example, integration testing doesn’t stop with the database load; test reads must verify that it was correctly loaded.

Integration testing also differs from system testing in that when a defect is discovered, not all previously executed tests have to be rerun after the repair is made. Only those tests with a connection to the defect must be rerun, but
retesting must start at the point of repair if it is before the point of failure. For example, the retest of a failed FTP process may use an existing data file instead of recreating it if up to that point everything else was OK.

Sample Entry and Exit Criteria for Integration Testing


Integration testing has a number of sub-types of tests that may or may not be used, depending on the application being tested or expected usage patterns.
♦ Compatibility Testing – Compatibility tests insures that the application works with differently configured systems based on what the users have or may have. When testing a web interface, this means testing for compatibility with different browsers and connection speeds.
♦ Performance Testing – Performance tests are used to evaluate and understand the application’s scalability when, for example, more users are added or the volume of data increases. This is particularly important for identifying bottlenecks in high usage applications. The basic approach is to collect timings of the critical
business processes while the test system is under a very low load (a ‘quiet box’ condition) and then collect the same timings with progressively higher loads until the maximum required load is reached. For a data retrieval application, reviewing the performance pattern may show that a change needs to be made in a stored SQL procedure or that an index should be added to the database design.
♦ Stress Testing – Stress Testing is performance testing at higher than normal simulated loads. Stressing runs the system or application beyond the limits of its specified requirements to determine the load under which it fails and how it fails. A gradual performance slow-down leading to a non-catastrophic system halt is the desired result, but if the system will suddenly crash and burn it’s important to know the point where that will happen. Catastrophic failure in production means beepers going off, people coming in after hours, system restarts, frayed tempers, and possible financial losses. This test is arguably the most important test
for mission-critical systems.
♦ Load Testing – Load tests are the opposite of stress tests. They test the capability of the application to function properly under expected normal production conditions and measure the response times for critical transactions or processes to determine if they are within limits specified in the business requirements and
design documents or that they meet Service Level Agreements. For database applications, load testing must be executed on a current production-size database. If some database tables are forecast to grow much larger in the foreseeable future then serious consideration should be given to testing against adatabase of the projected size.

Performance, stress, and load testing are all major undertakings and will require substantial input from the business sponsors and IT staff in setting up a test environment and designing test cases that can be accurately executed. Because of this, these tests are sometimes delayed and made part of the User Acceptance Testing phase. Load tests especially must be documented in detail so that the tests are repeatable in case they need to be executed several times to ensure that new releases or changes in database size do not push response times beyond
prescribed requirements and Service Level Agreements.

USER ACCEPTANCE TESTING (UAT)
User Acceptance Testing is also called Beta testing, application testing, and end-user testing. Whatever you choose to call it, it’s where testing moves from the hands of the IT department into those of the business users. Software vendors often make extensive use of Beta testing, some more formally than others, because they can get users to do it for free.

By the time UAT is ready to start, the IT staff has resolved in one way or another all the defects they identified. Regardless of their best efforts, though, they probably don’t find all the flaws in the application. A general rule of
thumb is that no matter how bulletproof an application seems when it goes into UAT, a user somewhere can still find a sequence of commands that will produce an error.

Nothing is foolproof. Fools are just too darn clever. - anonymous

To be of real use, UAT cannot be random users playing with the application. A mix of business users with varying degrees of experience and subject matter expertise need to actively participate in a controlled environment.
Representatives from the group work with Testing Coordinators to design and conduct tests that reflect activities and conditions seen in normal business usage. Business users also participate in evaluating the results. This insures that the application is tested in real-world situations and that the tests cover the full range of business usage. The goal of UAT is to simulate realistic business activity and processes in the test environment.

A phase of UAT called “Unstructured Testing” will be conducted whether or not it’s in the Test Plan. Also known as guerilla testing, this is when business users bash away at the keyboard to find the weakest parts of the application. In effect, they try to break it. Although it’s a free-form test, it’s important that users who participate understand that they have to be able to reproduce the steps that led to any errors they find. Otherwise it’s of no use.

A common occurrence in UAT is that once the business users start working with the application they find that it doesn’t do exactly what they want it to do or that it does something that, although correct, is not quite optimal. Investigation finds that the root cause is in the Business Requirements, so the users will ask for a change. During UAT is when change control must be most seriously enforced, but change control is beyond the scope of this paper. Suffice to say that scope creep is especially dangerous in this late phase and must be avoided.

Sample Entry and Exit Criteria for User Acceptance Testing


PRODUCTION VERIFICATION TESTING
Production verification testing is a final opportunity to determine if the software is ready for release. Its purpose is to simulate the production cutover as closely as possible and for a period of time simulate real business activity. As a sort of full dress rehearsal, it should identify anomalies or unexpected changes to existing processes introduced by the new application. For mission critical applications the importance of this testing cannot be overstated.

The application should be completely removed from the test environment and then completely reinstalled exactly as it will be in the production implementation. Then mock production runs will verify that the existing business process flows, interfaces, and batch processes continue to run correctly. Unlike parallel testing in which the old and new
systems are run side-by-side, mock processing may not provide accurate data handling results due to limitations of the testing database or the source data.

Sample Entry and Exit Criteria for Production Verification Testing


REGRESSION TESTING

Bugs will appear in one part of a working program immediately
after an 'unrelated' part of the program is modified -
Murphy

Regression testing is also known as validation testing and provides a consistent, repeatable validation of each change to an application under development or being modified. Each time a defect is fixed, the potential exists to inadvertently introduce new errors, problems, and defects. An element of uncertainty is introduced about ability of the application to repeat everything that went right up to the point of failure. Regression testing is the probably selective retesting of an application or system that has been modified to insure that no previously working components, functions, or features fail as a result of the repairs.

Regression testing is conducted in parallel with other tests and can be viewed as a quality control tool to ensure that the newly modified code still complies with its specified requirements and that unmodified code has not been affected by the change. It is important to understand that regression testing doesn’t test that a specific defect has been fixed. Regression testing tests that the rest of the application up to the point or repair was not adversely affected by the fix.

Sample Entry and Exit Criteria for Regression Testing