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What is Error Guessing Software Testing

November 7, 2017 Types of Testing
Error Guessing, how to error guess in software testing, guess an error, testing technique, out-of-box, think outside the box

First of all, it is quite important to know that “Error guessing” is a testing technique which is a type of black box testing technique and very helpful in the situations where other black box testing techniques such as boundary value analysis and equivalence partitioning are not able to cover all the scenarios which are prone to error in the application. Error guessing comes with the extensive experience in software testing field.

There are many hidden errors which are quite difficult to be found during the formal testing process. Testers need to go out of the way to find out these hidden bugs by using their experience or intuition. This type of testing is called Error guessing.

Many times it happens that requirement document does not cover all the possible scenarios and conditions which ultimately lead to the loophole in the application even after development and also sometimes remain undetected informal testing process.

“Error guessing” is generally done on the basis of the prior testing experience of a similar software application. Test cases prepared totally rely upon software testers involved in this type of testing, who uses past experience and intuition to determine the situation which causes software failure. Test cases are designed based on those situations, as per understanding of software tester, doing “Error guessing” testing.

It is very important to know that guessing of errors is quite difficult for untrained testers or less experienced testers. Use of this technique becomes better with the increase in experience.

In “Error guessing” technique, software testers test the application by going out of the box and not following what is given in requirement document because of inexperienced testers, while adhering to requirement document start following traditional approach and do not think out of the way and perform normal testing.

Experienced testers may find the error anywhere whether it is requirement document, design document, testing document or while performing testing itself. Experienced testers deviate little from normal testing and can perform some testing where they think they can find an error.

It is common belief that good testers do not guess and follow a traditional testing approach like preparing test cases based on functional document or any other required document provided and executing them in order to find bugs in the application, which is not true.

Factors affecting Error Guessing

There are many factors which help in designing test cases for “Error guessing” or helps in finding defects while testing. Some of them are as below

  • Previous experience of testing similar applications
  • Understanding of the system under test
  • Knowledge of typical implementation errors
  • Previously troubled areas
  • Historical data
  • Test results

One more thing to be noted that “Error guessing” technique does not guarantee full coverage of test cases and has to be done with other types of traditional testing to ensure the quality product.

“Error guessing” has no particular technique and tools. It is simply done from the mind of experienced testers. Now for using “Error guessing” technique more efficiently, testers are required to improve technical understanding of the application. Testers can talk with developer, understand code architecture and design patterns

Now one more thing which is important to know that error guessing is not done only for checking error in the code but also can exist in any phase of software development lifecycle such as requirement phase, design phase, testing phase, implementation phase.

Typical Errors found during Error Guessing Testing

Error guessing may be considered as test method in which test cases are designed in such a way that it can be used to find bugs in the program as well based on prior testing. Typical errors include divide by zero, null pointer exception, invalid parameter etc. This type of exceptions can be produced in the application by following actions

  • Division by zero
  • Entering blank spaces in the input Form fields
  • Pressing submit button without entering values in the form.
  • Exceeding maximum limits in the input fields.
  • Any wrong data(maybe special characters) in the input fields of the form

Why Error Guessing

“Error guessing” technique plays a very important role when applied with other software testing techniques. Though it is not complete in itself and is more effective after formal testing is done because it has the capability to identify bugs that are not found in formal testing. “Error guessing” technique helps us to find the hidden defects. “Error guessing” helps in finding more issues/ defects by testing limited features only and with less effort and time. In fact, error guessing brings value added to the application and make the application more powerful and robust.


Overall we can say that “Error guessing” is a black box testing technique which requires experience tester to find out error-prone areas in the application based on his experience and error guessing capability which only comes out of the experience. The inexperienced tester does not have the capability to make such guesses and generally follow traditional test Management process like test case preparation from requirement document, test case execution, defect reporting, etc.

About the author

RamPrakash Singh author

Ram Prakash has worked in various domains of testing including security, performance, security testing and automation testing. Including several tools like QTP, selenium, LoadRunner,JMeter, VSTS Coded UI, soap UI, Burp Suite etc.

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