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What the heck is black box testing?

What the heck is black box testing?

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Black box testing is kind of a fancy way of saying “have someone use your app and see if it works right.”

It’s a method of testing the requirements and functionality of software without the knowledge of its internal structure. Meaning, the tester has no prior understanding of the software’s database structure, programming language, or server. It doesn’t peer into the inner workings or structure of the app. Rather, it tests how it functions from an end user’s perspective.

It’s also known as closed box, opaque, behavioral, and specification-based testing. It differs from other testing methods in that it only compares the outcome to the intended result without identifying what went wrong if a test fails.

An example would be someone visiting an app, inputting their email, selecting a “sign up” button, then comparing the outcome to the intended results. In this process, they’re looking for a predetermined result like a confirmation screen or a specific next step in the onboarding process.

Here’s a deeper look at what black box testing is and why people use it.

Why people use black box testing

An advantage of black box testing is that the tester doesn’t need technical or coding know-how. Anyone can do it. Because they’re only looking at one thing (“if Y does X”), testers can find and report issues quickly. It’s the behavior testing of software.

White box testing techniques, on the other hand, are functional tests of the structure of the code. In white box testing, the tester is typically a software engineer and has knowledge of how the technology works—the internal structure or code. You could test an algorithm, for example, with white box testing. Whereas with black box tests, you can only test user functions.

Read more about the differences between white box and black box testing on geeksforgeeks.org.

Black box testing is used because anyone can check to see if a feature is functioning as intended. If the test fails, it’s up to the engineering team to explore what went wrong.  

Popular black box testing techniques

Black box testing techniques can be functional or non-functional. Here are the typical black box testing techniques used.

  1. Equivalence class partitioning: designed to reduce the total number of test cases to be developed (therefore reducing redundancies and time to test) by defining test cases that uncover classes of errors. It divides the input data of a software unit into partitions of equivalent data from which test cases can be derived.
  2. Decision table testing: a visual matrix depicting different sets of input combinations and their expected outcome on each row. They test an application’s behavior based on specific inputs.
  3. Cause-effects graphs: graphically illustrates the relationship between effects and causes, identifying all the factors that influence the particular outcome.
  4. Boundary value analysis: the most commonly used black box testing technique. A form of functional testing focused on determining and testing at chosen boundaries for input values. Boundary values include just inside/outside of the boundaries, typical values, error values, maximum, and minimum.
  5. Error guessing: the software tester uses their past experience to determine where errors in the software may be. Test cases are then designed to find those errors and any lingering bugs.

So you want to save engineering time? (black box testing alternatives)

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