Even programming languages have bugs!

Why have I never thought of bugs in a programming language? How can I use it if I have a list of known bugs? And how can I test it to find bugs in a programming language?

These questions were running through my mind when Michael Bolton presented the bugs that he had observed in Perl and Javascript during the Rapid Software Testing Explored class. I immediately browsed about bugs in programming languages and found a bug database for Python and Java.

Here are the links:



I came to know that bugs may be caused by the compiler when it’s interpretation with the programming language  goes wrong. The information that I got from these links made me really curious to explore testing programming languages deeper.

A good example from “Explore it” book:

In the  “Explore It” book, I found a dedicated chapter for exploring programming languages and APIs called “Explore when there is no user Interface” by the author Elisabeth Hendrickson who has shared her own experience beautifully. For example, she has explored the sort function from Javascript and tried several variations with it. 

She found that the numbers have been sorted as characters. So she has used an additional function within the sort to sort numbers. She has beautifully explained that exploring techniques help to uncover more behavior about a particular function from a programming language and it’s limitations. 

My observations with python:

Similarly, I have found a known limitation with Python during a training session I had in my office. When assigning a=2 and giving help(a), it’s possible to see info about the integer class. 

And it’s the same behavior for float class also if I try to give x = 1.5.

But if it’s assigned with a string such as b = “hello”, it’s not possible to see it’s info. So instead help(str) has to be used.

It has been observed as an inconsistent behavior as for other data types; the details can be fetched easily using the help() command in the python console.

List of common bugs mentioned by Cem Kaner:

I have also seen some list of bugs that can be observed in a programming language from the appendix page of Cem Kaner’s book “Testing computer software”. I found this one really useful for me when exploring loops and conditions during programming.

This list really helps in recognising the problems that we might face when using loops and conditionals.There is a huge list of common bugs that can be really useful not only for testing software but also for programming languages. 

A piece of suggestion from Michael Bolton:

I have received a great piece of suggestion from Michael Bolton when I had a separate discussion with him regarding this. He shared that bugs in a programming language might affect many people like developers, testers, technical support and for the people to whom they were writing code.

From the above information, I have understood that knowing how to test a programming language might help testers in many ways. When they are writing automation code, it would be easy for them to analyse the issue if the issue is coming from automation script , the programming language or from the software that they are testing. Besides that, it would help them to test APIs effectively if they have some knowledge on test design techniques to identify bugs in API. As mentioned earlier, bugs in a programming language can be caused by compilers as well. So having a list of bugs in a programming language would help testers during risk analysis.

I hope my fellow testers find this article helpful and would like to know your experience finding bugs in a programming languages.


  1. Explore It!: Reduce Risk and Increase Confidence with Exploratory Testing by Elisabeth Hendrickson-https://www.amazon.in/Explore-Elisabeth-Hendrickson/dp/1937785025
  2. Testing computer software by Cem Kaner, Jack Falk and Hung Q. Nguyen-https://www.amazon.in/Testing-Computer-Software-Cem-Kaner/dp/0471358460

About Author

Success! You're on the list.

5 thoughts on “Even programming languages have bugs!

Add yours

Leave a Reply

Up ↑

%d bloggers like this: