How to Test a simple Calculator Interview Question

This is a very common interview question and was very much expected when I appeared for my telephonic interview with Microsoft! And as expected I was asked this J “How would you test a calculator that does basic operations like addition, multiplication, division, subtraction and square root.

So here is a reasonable answer to ace this question. Testing formally is divided into two broad categories Functional testing and Non-Functional Testing.  To be very honest interviewer is NOT interested in how much you know about different types of testing rather they want to see how you’re thinking pattern works.

A model answer to this question can be as follows:

“To test a calculator it’s very important that we test both its functional aspects as well as non-functional requirements.  First I would be testing its functional aspects as follows:

a) Perform valid simple arithmetic operations on numbers and compare results with actual results

b) BODMAS: use a long string of different operations on numbers and see if it follows the BODMAS principle and calculates result accurately

c) Try dividing a number by zero and see the output

d) Calculate square root for a negative number and see the result.

e) Perform mathematical operations on very large numbers and see how it handles them.

f) Press and test the back button it should delete the last digit and update screen.

g) Clear button should reset the screen to zero.

h) Use of appropriate error messages.

i) Other aspects such as weight of the calculator should be as such as that it’s easy to carry; display screen should display the numbers big enough for proper visibility and durability of the product.

I hope it helps!


  1. Gustavo said

    Hey, Im also a new SDET hire for Microsoft. I will start this October.

    Are you at Redmond yet?

  2. Faizan said

    Nice description… Thanx man.. 🙂

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