What is Error Guessing Technique?

Error Guessing is a Software Testing technique on guessing the error which can prevail in the code.

It is an experience-based testing technique where the Test Analyst uses his/her experience to guess the problematic areas of the application. This technique necessarily requires skilled and experienced testers.

It is a type of Black-Box Testing technique and can be viewed as an unstructured approach to Software Testing.

Error guessing technique

Error Guessing Technique

The test cases for finding issues in the software are written based on the prior testing experience with similar applications. So, the scope of the test cases would generally depend upon the kind of testing Test Analyst was involved in the past. The Error Guessing technique does not follow any specific rules.

For Example, if the Analyst guesses that the login page is error-prone, then the testers will write detailed test cases concentrating on the login page. Testers can think of a variety of combinations of data to test the login page.

To design test cases based on the Error Guessing technique, the Analyst can use past experiences to identify the conditions.

This technique can be used at any level of testing and for testing the common mistakes like:

  • Divide by zero
  • Entering blank spaces in the text fields
  • Pressing the submit button without entering values.
  • Uploading files exceeding maximum limits.
  • Null pointer exception.
  • Invalid parameters

The achievement rate of this technique does mainly depends upon the ability of testers.

Purpose Of Error Guessing In Software Testing

  • The main purpose of this technique is to guess possible bugs in the areas where formal testing would not work.
  • It should obtain an all-inclusive set of testing without any skipped areas, and without creating redundant tests.
  • This technique compensates for the characteristic incompleteness of Boundary Value Analysis and Equivalence Partitioning techniques.

Error guessing technique

Factors Used To Guess The Errors

Error Guessing technique requires skilled and experienced tester. It is mainly based on intuition and experience.

Factors used to guess the errors

Following factors can be used to guess the errors:

  • Lessons learned from past releases
  • Tester’s intuition
  • Historical learning
  • Previous defects
  • Production tickets
  • Review checklist
  • Application UI
  • Previous test results
  • Risk reports of the application
  • Variety of data used for testing.
  • General testing rules
  • Knowledge about AUT

When to perform Error Guessing?

It should be usually performed once most of the formal testing techniques have been applied.

Guidelines For Error Guessing

  • Remember previously troubled areas: During any of your testing assignments, whenever you come across an interesting bug, note it down for your future reference. There are generally some common errors that happen in a specific type of application. Refer to the list of common errors for the type of application you are working on.
  • Improve your technical understanding: Check how the code is written and how the concepts like a null pointer, arrays, indexes, boundaries, loops, etc are implemented in the code.
  • Gain knowledge of the technical environment (server, operating system, database) in which the application is hosted.
  • Do not just look for errors in the code but also look for errors and ambiguity in requirements, design, build, testing and usage.
  • Understand the system under test
  • Evaluate historical data and test results
  • Keep awareness of typical implementation errors

Procedure For Error Guessing Technique

Error Guessing is fundamentally an intuitive and ad-hoc process; hence it is very difficult to give a well-defined procedure to this technique. The basic way is to first list all possible errors or error-prone areas in the application and then create test cases based on that list.

Error Guessing Example

Suppose there is a requirement stating that the mobile number should be numeric and not less than 10 characters. And, the software application has a mobile no. field.

Now, below are the Error Guessing technique:

  • What will be the result if the mobile no. is left blank?
  • What will be the result if any character other than a numeral is entered?
  • What will be the result if less than 10 numerals are entered?

Advantages of Error Guessing technique

  • Proves to be very effective when used in combination with other formal testing techniques.
  • It uncovers those defects which would otherwise be not possible to find out, through formal testing. Thus, the experience of the tester saves a lot of time and effort.
  • Error guessing supplements the formal test design techniques.
  • Very helpful to guess problematic areas of the application.

Drawbacks of Error Guessing technique

  • The focal shortcoming of this technique is that it is person dependent and thus the experience of the tester controls the quality of test cases.
  • It also cannot guarantee that the software has reached the expected quality benchmark.
  • Only experienced testers can perform this testing. You can’t get it done by freshers.


Though Error Guessing is one of the key techniques of testing, it does not provide full coverage of the application. It also cannot guarantee that the software has reached the expected quality benchmark.

This technique should be combined with other techniques to yield better results. For doing this testing, it is essential to have skilled and experienced testers.

A significant advantage of this testing technique is that it uncovers the defects in the areas which otherwise remains undetected by other formal testing technique.