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README.rst

Freshen

  • Freshen is an acceptance testing framework for Python
  • It is built as a plugin for Nose
  • It uses the (mostly) same syntax as Cucumber

Most of the information shown here can also be found on the Cucumber wiki, but here it is anyway:

Freshen tests are composed of two parts: feature outlines and step definitions.

Feature outlines

Feature outlines are text files with a .feature extension. The purpose of this file is to describe a feature in plain text understandable by a non-technical person such as a product manager or user. However, these files are specially formatted and are parsed by Freshen in order to execute real tests.

You can put your feature files anywhere you want in the source tree of your project, but it is recommended to place them in a dedicated "features" directory.

A feature file contains the feature name with a free-form text description, followed by one or more scenarios or scenario outlines.

Scenarios

A scenario is an example of an interaction a user would have as part of the feature. It is comprised of a series of steps. Each step has to start with a keyword: "Given", "When", "And", or "Then". Here's an example for a calculator application (this example is included in the source code):

Scenario: Divide regular numbers
  Given I have entered 3 into the calculator
  And I have entered 2 into the calculator
  When I press divide
  Then the result should be 1.5 on the screen

Scenario Outlines

Sometimes it is useful to parametrize a scenario and run it multiple times, subsituting values. For this purpose, use scenario outlines. The format is the same as a scenario, except you can indicate places where a value should be subsituted using angle brackets: < and >. You specify the values to be substituted using an "Examples" section that follows the scenario outline:

Scenario Outline: Add two numbers
  Given I have entered <input_1> into the calculator
  And I have entered <input_2> into the calculator
  When I press <button>
  Then the result should be <output> on the screen

Examples:
  | input_1 | input_2 | button | output |
  | 20      | 30      | add    | 50     |
  | 2       | 5       | add    | 7      |
  | 0       | 40      | add    | 40     |

In this case, the scenario will be executed once for each row in the table (except the first row, which indicates which variable to subsitute for).

Step Definitions

When presented with a feature file, Freshen will execute each scenario which involves iterating over each step in turn an executing its step definition. Step definitions are python functions adorned with a special decorator. Freshen knows which step definition function to execute by matching the step's text against a regular expression associated with the definition. Here's an example of a step definition file, which hopefully illustrates this point:

from freshen import *
from freshen.checks import *

import calculator

@Before
def before(sc):
    scc.calc = calculator.Calculator()
    scc.result = None

@Given("I have entered (\d+) into the calculator")
def enter(num):
    scc.calc.push(int(num))

@When("I press (\w+)")
def press(button):
    op = getattr(scc.calc, button)
    scc.result = op()

@Then("the result should be (.*) on the screen")
def check_result(value):
    assert_equal(str(scc.result), value)

In this example, you see a few step definitions, as well as a hook. Any captures (bits inside the parentheses) from the regular expression are passed to the step definition function as arguments.

Freshen will look for step definition modules in every directory where it finds .feature files. The module should be named steps. It can also be a python package, as long as all the relevant functions are imported into steps/__init__.py.

Hooks

It is often useful to do some work before each step or each scenario is executed. For this purpose, you can make use of hooks. Identify them for Freshen by adorning them with "@Before", "@After" (run before or after each scenario), or "@AfterStep" which is run after each step.

Context storage

Since the execution each scenario is broken up between multiple step functions, it is often necessary to share information between steps. It is possible to do this using global variables in the step definition modules but, if you dislike that approach, Freshen provides three global storage areas which can be imported from the freshen module. They are:

  • glc: Global context, never cleared - same as using a global variable
  • ftc: Feature context, cleared at the start of each feature
  • scc: Scenario context, cleared at the start of each scenario

These objects are built to mimic a JavaScript/Lua-like table, where fields can be accessed with either the square bracket notation, or the attribute notation. The they do not complain when a key is missing:

gcc.stuff == gcc['stuff']  => True
gcc.doesnotexist           => None

Multi-line arguments

Steps can have two types of multi-line arguments: multi-line strings and tables. Multi-line strings look like Python docstrings, starting and terminating with three double quotes: """.

Tables look like the ones in the example section in scenario outlines. They are comprised of a header and one or more rows. Fields are delimited using a pipe: |.

Both tables and multi-line strings should be placed on the line following the step.

They will be passed to the step definition as the first argument. Strings are presented as regular Python strings, whereas tables come across as a Table object. To get the rows, call table.iterrows().

Tags

A feature or scenario can be adorned with one or more tags. This helps classify features and scenarios to the reader. Freshen makes use of tags in two ways. The first is by allowing selective execution via the command line - this is described below. The second is by allowing hooks to be executed selectively. A partial example:

>> feature:

@needs_tmp_file
Scenario: A scenario that needs a temporary file
    Given ...
    When ...

>> step definition:

@Before("@needs_tmp_file")
def needs_tmp_file(sc):
    make_tmp_file()

Ignoring directories

If a directory contains files with the extension ".feature" but you'd like Freshen to skip over it, simply place a file with the name ".freshenignore" in that directory.

Using with Django

Django is a popular framework for web applications. Freshen can work in conjunction with the django-sane-testing library to initialize the Django environment and databases before running tests. This feature is enabled by using the --with-django option from django-sane-testing. You can also use --with-djangoliveserver or --with-cherrypyliveserver to start a web server before the tests run for use with a UI testing tool such as Selenium.

Using with Selenium

Selenium is a widely used UI testing framework. You can make use of this framework in Freshen tests. To do so, include web.use_selenium() at the top of your step definition module. There is and example in the source code. You can pass the following options:

web.use_selenium(host="localhost", port=4444, browser="*firefox", url="http://localhost", tags=[])

The tags option will cause Selenium to only start for scenarios which match the given tags.

When enabled, you can find the Selenium API object in glc.browser.

Running

Freshen runs as part of the nose framework, so all options are part of the nosetests command- line tool.

Some useful flags for nosetests:

  • --with-freshen: Enables Freshen
  • -v: Verbose mode will display each feature and scenario name as they are executed
  • --tags: Only run the features and scenarios with the given tags. Tags should follow this option as a comma-separated list. A tag may be prefixed with a tilde (~) to negate it and only execute features and scenarios which do not have the given tag.

You should be able to use all the other Nose features, like coverage or profiling for "free". You can also run all your unit, doctests, and Freshen tests in one go. Please consult the Nose manual for more details.

Additional notes

Why copy Cucumber? - Because it works and lots of people use it. Life is short, so why spend it on coming up with new syntax for something that already exists?

Why use Nose? - Because it works and lots of people use it and it already does many useful things. Life is short, so why spend it reimplementing coverage, profiling, test discovery, and command like processing again?

Can I contribute? - Yes, please! While the tool is currently a copy of Cucumber's syntax, there's no law that says it has to be that forever. If you have any ideas or suggestions (or bugs!), please feel free to let me know, or simply clone the repo and play around.

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