Automated testing in C++ with Google Tests.

Jul 15, 2019

The goal of testing is to verify the correctness, reliability and stability of an application.

Types of testing

  1. Unit testing
  2. Integration testing
  3. Acceptance testing

As developers we perform only unit testing and integration testing.

Unit testing is used to isolate a block of code and test it. Integration testing used is for verifying the correctness of an application when integrated with other components. Acceptance testing is used by the end user to test the software for accepting it.

Grouping test suites

The tests are grouped as:

  1. Functional tests to verify the working of an application for a set of correct inputs.
  2. Error handling tests to verify the error handling abilty of an application for a set of error inputs.
  3. Input combination tests to verify the behavior and correctness of an application for all possible inputs.
  4. Boundary tests to verify the edge cases and limits of an application.
  5. Performance tests to verify time and space requirements of an application.

Block diagram

Automated unit testing block diagram

Example: Correct the Spelling app

Let’s take a sample application which corrects the spelling when you give it a word in english. This application is used to solve the jumbled words puzzle. It was written by me when I could not solve the jumbled words puzzle sent to me by my friends.

Today we use this application to learn how to automate unit testing using the Google Tests library.

Brief discussion of the app

The code for the application is hosted on github at CTS.

  • Application corrects the spelling (CorrectSpell.cpp).
  • Dependents NA, (main.cpp).
  • Dependencies spell checker libraries such as Gnu’s Aspell (AspellChecker.cpp).
  • Test Code tests for main code (test_CorrectSpell.cpp).
  • Mock Dependencies not used but maybe required to mock aspell.

The code for the application logic is self explanatory and it is in inc and src folders. The code for automating unit testing using GoogleTests is written in test/test_CorrectSpell.cpp file. The test code for other interfaces such as the spell checker interface and spell checker classes are not written to save my time.

You are encouraged to implement the same and hence learn to use Google Tests library to automate testing for C++ applications.

The screenshot of the test binary test_CorrectTheSpelling executed in my system is provided below for your reference.

Google Tests screenshot


To learn more about automated unit testing using Google Tests in real world applications go through the test code in OpenCV. It uses Google Tests with some modifications to automate the testing process for the entire opencv library. The opencv library is big enough to provide us with the immense intricate knowledge required to implement an automated testing system.

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