How do we know our code is reliable?

How do we know it returns an expected response?

How do we know our code plays nicely with other modules and scripts?

We test!

Why do we Test?

  • To know that new code produces the expected results

  • Just as with any research, we want to ensure our results are reliable, reproducible and trustworthy.

  • As software grows, our codebase becomes bigger and more complex.

  • When we rewrite and update code, we want to know that our new code works as intended, both in its basic functionality and as part of a bigger web of dependencies.

  • Writing tests for your software will save you time and headaches in the long run

When do we test?

  • Tests should be written alongside code, one test per ‘unit’ of code

  • In Python, a ‘unit’ would generally be considered to be a function or class

  • Any time that you manually run something and check the result

  • But! Tests can be written before we write any code, this is known as Test Driven Development (TDD)

  • By writing tests alongside your code, we know that as long as our tests are passing, our previously written code doesn’t need to be revisited

Types of test

Unit Test *

Integration Test

Regression Test

Performance Test

How to test

  • In Python, pytest is the most popular framework

  • In the next exercise we’ll produce a unit test for a function, using pytest