c++ – Guidelines for writing a test suite – Education Career Blog

What are the best practices/guidelines for writing test suite for C++ projects?

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This is a very broad question. For unit testing and Test Driven Development (TDD), there is some useful (if somewhat platidinous in parts) guidance on this from Microsoft – you can overlook the Visual Studio-specific advice, if it does not apply.

If you are looking for guidance on system or performance testing, I would clarify your question. There is a decent broader rationale in the docs for Boost.Test.

There are several unit testing best
practices to review before we close.
Firstly, TDD is an invaluable
practice. Of all the development
methodologies available, TDD is
probably the one that will most
radically improve development for many
years to come and the investment is
minimal. Any QA engineer will tell you
that developers can’t write successful
software without corresponding tests.
With TDD, the practice is to write
those tests before even writing the
implementation and ideally, writing
the tests so that they can run as part
of an unattended build script. It
takes discipline to begin this habit,
but once it is established, coding
without the TDD approach feels like
driving without a seatbelt.

For the tests themselves there are
some additional principals that will
help with successful testing:

Avoid creating dependencies between
tests such that tests need to run in a
particular order. Each test should be
autonomous.

Use test initialization
code to verify that test cleanup
executed successfully and re-run the
cleanup before executing a test if it
did not run.

Write tests before
writing the any production code
implementation.

Create one test class
corresponding to each class within the
production code. This simplifies the
test organization and makes it easy to
choose where to places each test.

Use
Visual Studio to generate the initial
test project. This will significantly
reduce the number of steps needed when
manually setting up a test project and
associating it to the production
project.

Avoid creating other machine
dependent tests such as tests
dependent on a particular directory
path.

Create mock objects to test
interfaces. Mock objects are
implemented within a test project to
verify that the API matches the
required functionality.

Verify that
all tests run successfully before
moving on to creating a new test. That
way you ensure that you fix code
immediately upon breaking it.

Maximize
the number of tests that can be run
unattended. Make absolutely certain
that there is no reasonable unattended
testing solution before relying solely
on manual testing.

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TDD is certainly one set of bests practices. When retrofitting tests, I aim for two things code coverage and boundary condition coverage. Basically you should pick inputs to functions such that A) All code paths are tested and better if all permutations of all code paths are tested(sometimes that can be a large number of cases and not really be necessary if path differences are superficially different) and B) That all boundary conditions(those are conditions that cause variation in code path selection) are tested if your code has an if x > 5 in it you test with x = 5, and x = 6 to get both sides of the boundary.

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