Black Box Testing

Introduction

Black box testing is a software testing approach that uses it to test the software without knowing the internal structure of the code or program. However, is this test enough to find all errors?

This testing method is usually the final part of software projects. In particular, the method has often been used to perform acceptance testing. Black box testing can be defined as a testing technique to test the functionality of an application without looking at:

• Internal code structure.
• Implementation details.
• Internal software paths. 

This type of testing is based entirely on what we know about the software requirements and the functional specificaties .

As a customer or user, we must take into consideration that you will be asked to accept the software at some point at the end of the project. To determine whether the software meets expectations, you must perform acceptance testing. Set aside plenty of time for this.

Black Box Software Testing

In fact, Black Box is not the name of the approach, but the name of the software we are testing. However, we treat software like a black box that we don't know what's inside. We can test almost any Black-Box computer system. For example, an operating system like Windows, a website like Google, a database like Oracle or our own business application.

Before we started testing, we did not investigate the internal structure of the software or the database. Additionally, we do all testing from the user's perspective. The tester is only aware of what the software is supposed to do. How under-the-hood processing occurs remains unknown. During testing, the tester is familiar with all possible inputs and expected outputs of the software. However, testers don't know how the application actually processes incoming requests and how output is generated. What testers do is just feed valid and invalid inputs. They then determine the correction based on the expected results. As a result, the test case must have been carefully considered in advance. All test cases that we have to test with such an approach, we therefore do based on the requirements and specifications.

What is the purpose of Black Box testing?

The main objective of Black Box is to determine whether the software meets the user's expectations or not. However, it is not intended for the user to change their expectations before testing.

With this test, we try to find errors in the following categories:

• Initialization and termination errors.
• Incorrect or missing functions.
• Interface errors.
• Errors in data structures or access to the external database.
• Behavior or execution errors.

Black Box testing the step-by-step plan

The steps below are generally followed to perform a Black Box test.

• Initially, we look at the system requirements and specifications.
• The tester creates valid inputs to determine whether the software handles them correctly.
• Additionally, it creates some invalid cases to determine whether the software is able to detect and reject them
• The tester then determines what output it expects for that input.
• Testers write test cases based on selected input.
• These test cases are presented to the software.
• The tester compares the actual output with the expected output.
• When the previously found defects are corrected, the test is restarted.
• This continues until the software is error-free.

Types of testing where black box testing is applied

We can apply the Black Box testing method to the following levels of software testing:

• Integration testing.
• System tests.
• Acceptance tests.

The earlier black box testing occurs in the development process, the more complex the black box will be. However, larger black boxes require more black box testing techniques.

Testing Techniques

The next black box testing techniques used to test the software application.

• Equivalence Partitioning: This is a software test design technique where we divide the input values into valid and invalid partitions. In doing so, we select representative values from each partition as a test case.
• Boundary analysis: This is a software testing analysis technique for determining limits for input values. This involves selecting input values that are located on the boundaries (just inside and outside the boundaries).
• Cause and effect graph: This is a development technique for software testing where we identify cases and effects. We generate a cause and effect graph and the test cases we generate accordingly.
• Decision Table Test : In a decision table, we place the causes and their effects in a matrix. Additionally, there is a unique combination of input values in each column.

Black Box Testing Tools

Black box testing tools are tools for recording and repeating test cases. We primarily use these tools during regression testing to determine whether bugs have been introduced into the new build that were not already present in the previous build.

These recording and playback tools capture test cases in the form of scripts like TSL, VB script, JavaScript, Perl etc.

The benefits of Black Box testing

• We conduct these tests from the user's perspective and help identify differences in specifications.
• Testers do not need to know programming languages ​​or know anything about implementing the software.
• We can perform testing independently of vendor consultants or developers. This results in an objective test report. Developers know their own software, which can lead to a certain blindness to software errors.
• Test cases can be done once specifications are complete.

The disadvantages

• We can test only a small number of possible test cases so that many program paths remain untested.
• In many cases, requirements or specifications are unclear, making test cases difficult to derive.
• If a vendor consultant or developer has already run a certain test case, it is sometimes unnecessarily run again. However, the customer is responsible for acceptance and must determine for themselves whether the software functions correctly.
• At Black Box Testing, we are never sure if we have tested every relevant corner of the software.

In short, black box testing is a very reliable test that also gives us an idea of ​​the software. Unfortunately, we won't find all the errors with it.