Minimalistic BDD in Python
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pyspecs - Minimalistic BDD in Python

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pyspecs is a testing framework that strives to achieve more readable specifications (tests) by leveraging some fancy syntactic sugar and auto-discovery of tests/specs. WARNING: version 2.0 introduces breaking changes if you've been using 1.0 or 1.1.

Installation is straightforward:

$ pip install pyspecs


$ easy_install pyspecs


$ git clone
$ cd pyspecs
$ python


The main tool for verifying behavior is an assertion of some kind. The simplest assertion can be made by using the built-in assert statement:

assert 42 == 'The answer the life, the universe and everything'

For readability this project provides a more fluent method for making assertions:

# These imported names are all synonyms for the class that
# provides fluent assertions (Should). Use whichever provides
# the best readability.  The general patter is:
# >>> the([value]).should.[condition_method]([comparison_args])
#  or...
# >>> the([value]).should_NOT.[condition_method]([comparison_args]) # negated!

from pyspecs import the, this, that, it

this(42).should.equal(42) # this passes

this([1, 2, 3]).should.contain(2) # this also passes

the(list()).should.be_empty() # passes

it(1).should_NOT.be_greater_than(100) # passes

# raises AssertionError, caught by framework, logged as failure

Writing complete specs

from pyspecs import given, when, then, and_, the

with given.two_operands:
    a = 2
    b = 3

    with when.supplied_to_the_add_function:
        total = a + b

        with then.the_total_should_be_mathmatically_correct:

        with and_.the_total_should_be_greater_than_either_operand:

    with when.supplied_to_the_subtract_function:
        difference = b - a

        with then.the_difference_should_be_mathmatically_correct:

    # cleanup is just based on scope
    del a, b, total, difference

Notice that the names of each step are supplied as dynamic attributes of the given, when, then, and and_ step keywords. These user-created attributes are used in the output (below). Here is a listing of words that can be used as steps:

  • given
  • provided
  • when
  • then
  • and_
  • so
  • therefore
  • however
  • as_well_as

These steps can be arranged in any order and hierarchy for compose a specification (spec). You can even create your own steps that suit your needs (see the source code for how that's done).

Execution of specs

Beyond providing the python library which will be explained below, installation provides a command-line script into the environment, meant to be invoked from the root of your project. The script will execute all specs in .py files ending in '' or '' or beginning with 'test'.

To run all tests once:


To begin an auto-test loop (runs all specs anytime a .py file is saved):

$ -w

Complete Example

There are some complete examples of specs, code, and output in the examples folder.