Black box testing is a curious kind of testing as it is somewhat mysterious to the person who is testing the product. The tester will not have any prior knowledge or information about the internal mechanisms of the system that will be tested. In a typical software testing environment, the tester will only know what the inputs are and the expected output. However, the tester will have no idea about the types of programs used to make the output possible.
Anyone can conduct black box testing because no programming knowledge is required to run the test. However, both software developer and the tester should work independent of each other so that they can avoid any type of bias related to the software.
Black box testing may make use of groups called test groups. The members of the group will arrive at the scene sometime during the software developmental stage. Planning for a session of black box testing can commence immediately when the specifications for the test are ready. However, you should note that this test is dissimilar to glass box testing or white box test (as popularly called).
In a typical white box testing scenario, the participants will gather their data from the program code. In addition, the test results will not be determined until such a time when the developers write the codes in their entirety. Both of these tests have their own merits and pitfalls; when used in combination, they will ensure a vastly improved testing ambience.
Black Box Testing Techniques
Coming back to the black box testing, you will need to learn and understand how it works and in what manner you can conduct the test. With some basic knowledge and skills, even you can conduct this test in an effective manner. For example, you may need to use randomly generated inputs to avoid guess work during the testing process.
In black box testing only the test range should be specified by the tester to disallow guess work about the methods of a particular function. In addition, you may also need to test the data that lies outside the selected range. This will help you guarantee that the program is sturdy and robust.
Black box testing needs refined testing for boundary cases including the top to bottom range. This will help you ascertain that both the highest and lowest inputs will produce the desired output. Testers will also need to look at the value of zero especially when you use it as an input. Black box testing is somewhat similar to stress testing where overloading the program will reach its maximum point in the real time system.
Black box testing should also include crash testing because it will enable the software developers to know more about the issues that can bring down the entire system. You may also need to include different test monitoring tools and equipments while conducting the black box tests. This will help you observe the types of tests that were conducted in the past so that you can avoid possible repetitions. Similarly, these tools and equipments will also help you track the outputs of the tests which will come to use while maintaining the software product.
Several other types of black box testing will come to use while testing the software. Some of them are transaction testing, the domain testing, the state testing, the syntax testing, and the logic testing. You can also make use of the finite machine as a useful guide to design and run very effective black box tests.
Some of the black box testing techniques also includes boundary value analysis, pair wise testing, case testing, equivalence partitioning, and decision table testing among others. Black box testing is a very useful testing method when you use it in combination with other tests.
Advantages of Black Box Testing
Probably the most significant advantage of using black box testing is that it is far more effective when you want to test a large amount of codes, because the tester will not need to look into each and every single area of the programming unit. Another merit of this test is that the tester will not have any prior knowledge about the internal mechanism of the system, including information about the implantation of the system. This will help the software developer to avoid any type of bias in the results obtained and pooled.
In addition, the software developer will not allow the tester to look at the programming language so that the tester will never know the type and kind of codes integrated in the software product. These simple, yet important advantages will ensure tests running on the end user’s point of view; it is always possible to look and listen to the specific needs and complaints made by the tester.
Black box testing has the ability to expose different ambiguities and differences those are present within the specifications of the program. This will help software developers avoid or remove any inconsistencies and deviations. Soon after conducting black box testing, you can make test cases that match the specific issues of software in relation with the completed specifications.
Disadvantages of Black Box Testing
With all those advantages, you can still find some noticeable disadvantages with this testing. Here are some of the disadvantages those are associated with black box testing:
- With black box testing, you can test a small portion of entire inputs.
- It takes a long time to test all possible input sources
- It is also very difficult to design and create test cases that ensure the effectiveness of the software. The tester will not have any specifications at hand that can be looked at the initiation of test case designing phase.
- There are possibilities of testers conducting repetitions of test inputs, because they will not know about the different strategies that were tried previously
- In addition, the nature of this test may leave lot of programs untested in the process.
- It is also very difficult to direct the software to a specific code because of its complex nature.
- In the end, many testing research facilities still use white box testing method.
Black box testing has the ability to complement other similar tests to enhance the usability of a software product.
General Guidelines for Using Black Box Testing
First, you need to clean the test from the stated requirements then you need to have additional tests that will be used for the structure such as the branch coverage. The next step is to conduct domain tests that are not covered by the previous tests. You can also use different special techniques such as the loop, state, etc whenever it is appropriate. The last is using dirty tests that have not been conducted previously to discover any errors in the system.
On the other hand, there are also hardware devices you need to have when you want to conduct black box testing. These hardware devices include amplifiers, power supplies, and other common electrical equipment. But if you want to conduct functional that is automated, then special hardware with your desired characteristics may be required so that you will be able to use it for production testing and design validation.
As you can see, black box testing can give you a glimpse of the end users’ perspective even at the start of the development stage of the software. Black box testing also enables you to design tests cases that are appropriate for the outside environment. You should also note that most black box testing is mostly functional as the test designer will be the one to select whether the input is valid or not.
In addition, black box testing can be applicable to any level of a software testing stage including unit testing, integration, system testing, and acceptance testing. And the higher the level of the test, the bigger and the more complex the black box will become. Black box testing also has the capacity to uncover the parts of the specifications that had not yet been implemented but still, it is nearly impossible to tell which program path has already been used.
It is undeniable that black box testing should be conducted by software developers because of all the advantages it will provide. It will also give software developers the necessary insights as to what they could do to improve the software with an outsider’s eyes.
It is possible to get the best possible test design when you use black box testing but you should also look into your particular situation because there are different levels of software development and other kinds of test may be more suitable for your software depending at which stage of development you are in. But as you can see above, black box testing does have its limitations so you should not be dependent on this single test alone. Rather, black box testing should be used together with other kinds of software testing methods so that your software will be effective and free of errors.