Negative testing is a method of testing an application or system that ensures that the plot of the application is according to the requirements and can handle the unwanted input and user behavior. Invalid data is inserted to compare the output against the given input.[1] Negative testing is also known as failure testing or error path testing. When performing negative testing exceptions are expected. This shows that the application is able to handle improper user behavior. Users input values that do not work in the system to test it's ability to handle incorrect values or system failure.
Purpose
The purpose of negative testing is to prevent the application from crashing and it also helps improve the quality of an application by detecting defects.
Negative testing helps you to improve the testing coverage of the application.
Negative testing makes the application more stable and reliable.
Negative testing together with positive testing allows users to test the application with any valid or invalid) input data.
Benefits of negative testing
Negative testing is done to check that product deals properly with the circumstance for which it is not programmed. The fundamental aim of this testing is check that how bad data is taken care of by the systems, and appropriate errors are shown to client when bad data is entered. Both positive and negative testing play important role. Positive testing ensures that application does what it is implied for and perform each function as expected. Negative testing is opposite of positive testing. Negative testing discovers diverse approaches to make the application crash and handle the crash effortlessly.
Example
If there is a text box that can only take numeric values but the user type to write letter, the correct behavior in this case "(Incorrect data) Please enter a number" message should be displayed to the user.
If user is to fill the name field, there are ground rules that name text is mandatory to fill, name box shouldn't have values other than alphabets (no numeric values and special characters). Negative test cases for the text would be Name having numeric values, name having special characters and nothing is written in that text field.
Parameters for writing Negative test cases
There are two basic techniques that help to write the sufficient test cases to cover the most of the functionalities of the system. Both these techniques are used in positive testing as well.
The two parameters are: * Boundary values analysis
Boundary indicates limit to something. In this parameter, test scenarios are designed in such a way that it covers the boundary values and validate how application behaves on these boundary values.
Example
If there is an application that accepts Ids ranging from 0-255.Hence in this scenario, 0,255 will form the boundary values. The values within the range of 0-255 will constitute the positive testing. Any inputs going below from 0 and input going above from 255 will be considered invalid and will constitute negative testing.
