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Negative Testing


Negative testing
Software development is by no means a child's play. It is all about writing long and intricate codes and then testing these complex codes to guarantee flawless and uninterrupted performance. Testing is a major feature of writing successful codes. Any cost cutting in testing phase will lead to a malfunctioning software which is the surest way to disaster. In this article, we shall discuss a unique testing technique known as Negative Testing.

What Is Negative Testing?

Negative Testing is a technique wherein the response of the software is evaluated when unexpected parameters are entered. In simpler terms, during Negative Testing, the performance of the application is tested using invalid data inputs. For example, numbers are entered in alpha-numeric fields and vice-versa. Similarly, skipping mandatory fields can also be a part of this test. In an ideal scenario, during such times, the application should show the error "Invalid data input".

Characteristics of Negative testing

Here, we are providing, some of the key features of the negative testing, which may be seen, as under:

  • It is done, with the purpose, of breaking the system, and to achieve a failure, in the functioning of a software product, by feeding negative data.
  • This type of testing, evaluates a software product, against the failed conditions.
  • It is, performed, to identify faults or loopholes and vulnerable areas, which may results, into software's failure.
  • It, is done, to ensure the stability of a software product, after being encountered with the input values, beyond the limit/scope or with the invalid input data.
  • Generally, the task of carrying out the negative testing, is being executed, by a tester.
  • It is, used, to assess the potential security breaches and exceptional handling mechanism.

Necessity Of Negative Testing

Quite often Negative Testing is also known as Error Path Testing or Failure Testing. The aim of this type of testing is to ensure suitable and optimum software performance even when the user behaves irrationally by entering invalid and inappropriate data. The idea is to help the user correct his or her error while entering incorrect data and guiding them to identify and rectify the said mistake. This makes for a stronger and more user-friendly application. As such, every software development firm that wishes to have a strong and competent software needs to undertake rigorous Negative Testing as well.

Negative Testing Techniques:

There are basically two techniques used by the team of testers for writing negative test cases. Both of these techniques are an integral part of the process of negative as well as positive testing and help define the input requirements. These techniques are:

  1. Boundary Value Analysis: Boundary value is a software testing technique, wherein test cases are designed to test an application, using values present at the boundary. When the input data used for test execution is picked outside the boundary value limits that it is said to be negative testing.
  2. Equivalence Partitioning: Equivalence Partitioning or Equivalence Class Partitioning (ECP) divides the input data into partitions of equivalent data for designing test cases for testing an application. These test cases are then used to cover each partition at least once. It is when the partitions with invalid values are used that it is termed as negative testing.

Top Negative Test Cases:

Negative test cases are another important component of negative testing, which are designed by the team to test the software product in ways in which it is not intended to be used. As this is done to ensure the stability and reliability of the software, these should be considered by the team in their testing efforts:

  1. Embedded Single Quote: Some software systems encounter issues when the users try to store information that consists of single quote. Therefore, for each screen that accepts alphanumeric data entry, the team should provide text that contains one or more single quotes.
  2. Data Bounds Test: It is important for the testing team to test all the lower as well as upper bounds for data fields.
  3. Field Size Test: The functional specifications should indicate the number of characters one can enter into a field. Write test cases to ensure that this limit is not exceeded. This helps in preventing users from entering more characters, rather than them getting error messages after they have exceeded the limit.
  4. Performance Changes: There should be performance tests executed by the team to identify the speed of the screens. Moreover, the test suite should include test cases that compare prior and current release performance statics, which could help in identifying potential performance problems.
  5. Numeric Bound Test: Again to ensure their accuracy, it is important for the team to test both the lower and upper bounds.
  6. Web Session Testing: As there are several web applications that depend on browser session to monitor various user information, the team creates test cases to launch web pages within the application that don’t require users to log in.
  7. Required Data Entry: Each field in the software that requires data entry on the screen should be tested before required data is entered in the field.

Common Negative Test Scenarios:

Negative testing improves the test coverage of a software application while detecting the possible application crashes in different situations. Some of these test scenarios and situation are:

  • Populating Required Fields.
  • Corresponding between Data Field Types.
  • Web Session Testing.
  • Reasonable Data.
  • Allowed number of special characters.

Benefits Of Negative Testing

It is quite an obvious fact that Negative Testing is beneficial for the final product launch. Although, the basic purpose of negative testing, is to make a software, function undesirably and differently from its expected working, on feeding with the invalid inputs, with the intention of break intothe system, but what may be other benefits, may be assimilated from the points mentioned below:

  • Functional Reliability Is Verified – Even under stress the software needs to perform within specified parameters. Negative Testing provides a chance to check the software for unexpected behaviours when the data variables are also inconsistent. This way corrective action can be taken timely and makes for increased reliability of the final product.
  • Ensures Error Validation – Negative Testing increases the likelihood of covering all bases and all types of errors that can arise due to erratic human behaviour. This leads to easy anticipation of all problem areas and prevents any unnecessary crashes. Also, this helps in validating errors and building appropriate responses that can guide the user towards the right path.
  • Makes For A Better Software – When the performance of the software remains unhindered even during those times when the data entered is incorrect, it makes for a better final product. Such a software is considered to be user-friendly and hence a potential hit.

Disadvantages of Negative Testing:

Though negative testing is beneficial for a software product and is part of every successful software development cycle, there are still some disadvantages of this software testing technique, such as:

  • It requires excessive time, money and efforts.
  • Creates unnecessary delays in the product release.
  • To create test cases, negative testing requires skilled and experienced testers.

Difference Between Negative and Positive Testing:

A comprehensive understanding of negative testing can be gathered only by comparing it with its counterpart positive testing. Therefore, listed below are some of the major differences between positive and negative testing.

Sl.No. Negative Testing Positive Testing
1. Negative testing or destructive testing is performed with invalid set of data. Unlike negative testing, positive testing is performed with valid set of values.
2. During this testing, the team always checks for invalid set of values. Positive testing is the process of checking for only valid set of inputs.
3. It is always done to break the application with unknown set of test conditions. It is always performed to verify the known set of test conditions in the software application.
4. It tests scenarios for which the product is not coded or designed, by providing invalid values. Valid set of data is provided by the team here to check how the application behaves.
5. This testing ensures the stability of the software by breaking it up. It ensures that the application works as per the software requirement specifications.

You can find several other differences between these two testing techniques in our article Positive Testing Vs Negative Testing.

Conclusion

Many a times people live under the misconception that Negative Testing is one more way of increasing expenses without any conceivable benefits. This ideology is fatal as it can compromise the quality of the final product. So, if you want to aim high, then it is best to never underestimate the power of any testing technique. In short, by enforcing Negative Testing you can improve the quality of the software and make it stronger.