peter-daly / assertive

A library for writing concise high quality assertions for tests

Assertive

Assertive is a testing library that provides declarative assertions to you python tests.

Core of assertive

Assertive is built on two core concepts:

1. Criteria
2. Assertions

Criteria

Criteria are declarative statements that can be used with assert statements to give a richer test experience.

assert 5 == is_greater_than(4)
assert 5 == is_odd()
assert 5 != is_even()

Criteria can also be composed with logical operators to give a richer experience in writing tests

assert 5 == is_greater_than(4) & is_less_than(6) # Using AND
assert 5 == is_even() | is_less_than(6) # Using OR
assert 5 == is_even() ^ is_odd() # Using XOR
assert 5 == ~is_even()  # Using INVERT

Assertions

Criteria can be used with python's inbuilt assert statement or you can also use Assertions from the assertive library. The key difference between assert and Assertions is that Assertions give a more detailed Assertion Error when the test fails.

To use Assertions you simple use the assert_that() function

assert_that(5).matches(is_greater_than(4))
assert_that(5).matches(is_odd())
assert_that(5).matches(is_greater_than(4) & is_odd())
assert_that(5).does_not_match(is_even())

assert 5 == is_greater_than(4)
assert 5 == is_odd()
assert 5 == is_greater_than(4) & is_odd()
assert 5 != is_even()