Black-Box Testing: Definition, Types & Techniques

Black-box testing lets you analyze how something works without digging into the way it's built.

You might use the method to ensure that your website works perfectly before you launch it. Or you might schedule a black-box test at multiple points during the app development process. 

Black-box testing has limits. Once you have the results, you'll need to unpack the code and find the right fixes. But if you perform regular, consistent black-box testing, you can make sure that your tools work both properly and consistently for your customers. 

What Is Black-Box Testing? 

Your team knows what your software, website, or app is supposed to do. As your team members work, they look for hiccups, glitches, or unexpected actions that could indicate a coding error. 

You could use black-box testing to find:

  • Omissions. Did you promise functionality that's missing? 
  • Errors. Does the interface work unexpectedly? Is the data source sound? 
  • Limits. Do certain inputs make the system crash or perform poorly? 

A black-box testing team has no idea how you built the testing subject, so they can't give you suggestions to fix any problems they find. Their only job is to highlight items that need more investigation.

If you need input on coding problems, which could make repairs quicker, white-box testing or pen testing might be a better choice. People who work on these teams know all about the code beneath a product, and their tests ensure your product works as you designed it. 

When Is Black-Box Testing Used? 

On one day in May 2020, thousands of people tried to launch apps on their phones and experienced crashes instead. Facebook's coders were to blame. Black-box testing could have prevented this catastrophic problem. 

Before you launch anything to the public, you should test it carefully and repeatedly. The work you do now could ensure that customers have less to complain about in the future. 

If you're building software, you'll run black-box tests multiple times. Testing is part of the software testing life cycle (STLC), and you typically perform it during the following stages:

  • Requirement: Software testers determine what elements of the product they can and can't test. 
  • Planning: Testers determine what sorts of tests will work best and how they will measure success. 
  • Analysis: Testers specify ideal test conditions. 
  • Design: They identify formal rules for each test. 
  • Implement: Testers create test cases.
  • Execution: Tests begin, and testers log defects. 
  • Conclusion: Formal reports end the cycle. 

Your product might go through this same process multiple times during development. Each test tells you a little more about what's working and what's broken. 

Black-box testing might also make you less vulnerable to hackers. Some of your tests should involve trying to break past security limitations, and any successful breach indicates that you have more to do to keep your data safe. You might run this form of repeated testing throughout the lifecycle of your product, just to ensure that everything remains secure. 

How to Do Black-Box Testing 

Modern projects involve dozens of people. Simply launching a new website, for example, could mean developing a team of 20 or more. Perform black-box testing, and you'll need even more participants. 

Black-box testers need access to:

  • Specifications. What should the product do? How should it function? 
  • Design parameters. What should it look like? How should it feel?
  • Inputs. What should the tester do to ensure the product works?
  • Outputs. What is an error? What is accurate? 

With this information, the tester will run test cases to ensure that everything works properly, and they will log all errors. 

Plenty of black-box test design techniques exist, including:

  • All-pairs testing. The tester has a pair of input parameters, and they test all combinations. 
  • Boundary value analysis. Testers have a range of inputs, and they use them exclusively as they work. 
  • Decision-table testing. Testers use different input combinations to test system behavior. They capture all data in a table. 
  • Domain analysis. Testers look over related software systems to find variable and common parts. 
  • Equivalence partitioning. The tester divides up input data and tests it in groups. They try to find underlying classes of errors. 
  • Error guessing. Experienced testers rely on their experience to find bugs in the software they’re analyzing now. 
  • Use-case testing. Your testing team tests specific actions or events to ensure they help users reach a specific goal. 
  • User-story testing. You give testers personas, and they work to see if that person could get satisfaction from the item they’re testing.

You could give your testers a combination of some of the techniques above. For example, you could blend use-case testing with decision tables. 

Remember to Test Often 

Experts say inadequate testing causes crashes. Any time your website, app, or program doesn't work as expected, you risk losing the trust and goodwill of your customers. Don't let it happen.

If security issues keep you from doing the testing your customers expect, let us help. At Okta, we're experts at helping companies just like yours to keep valuable data safe and secure. Find out more


Several Major iOS Apps Crashing at Launch Due to Facebook SDK Issues. (May 2020). Tech Crunch. 

Why Hackers Know More About Our Systems. (2011). System Assurance. 

The Top 6 Reasons Mobile Apps Crash: How to Best Avoid Murphy. TechBeacon. 

How to Organize and Prepare Your Team for a Web Redesign Project. Fastspot.