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fresher 0.4.0

Clone of the Cucumber BDD framework for Python forked from Freshen

Fresher

Fresher is a fork of Freshen. As of Fall of 2013, Freshen appeared to no longer being maintained, so I decided to fork and make some much needed changes.

Differences from Freshen:

  • Fresher is tested against Python 3.3, Python 2.7 and Python 2.6. (It seems Freshen was tested against whatever Python happened to be around. It definitely did not work on Python 3.)

  • The file to get Fresher to ignore a directory is .fresherignore.

  • All arguments that are specific to Fresher begins with --fresher- so:

    • --tags is now --fresher-tags
    • --language is now --fresher-language
    • --list-undefined is now --fresher-list-undefined

    This change allows using fresher and freshen together in the same installation, and reduces the chances of conflicts with other nose plugins in the future.

  • Undefined steps are fatal errors unless you pass --fresher-allow-undefined.

  • Freshen would load steps files under fake module names. Fresher loads the whole shebang under freshen.steps.

Warning

Do not have a steps module loaded by Fresher also be loaded by no-step modules. (A no-step module is one which does not implement steps). Here's a scenario where you could run into trouble: module A features/steps loads module B features/util (a nostep module) which loads module C features/nested/steps which is also a steps module for another set of features. We could call this an S-N-S scenario (steps, no-step, steps). If you do this then module C will be loaded twice: once because module B imports it and a second time when fresher finds it is needed for some features in the nested subdirectory. It will be loaded as two different modules. If the duplicated module maintains no state, you'll only incur the cost of loading the same module twice. However, if it does maintain state, then good luck.

Note that Freshen 0.2 also suffers from this problem due to the fake module names it uses. I believe behave 1.2.3 also suffers from this problem. It uses exec to load step definition files. In an S-N-S case like the one above, module A will be exec'ed, and module B will import module C so module C will show as an actual Python module. Then when behave determines that C is needed for step definitions, it will exec it, thereby loading it again.

It is completely fine if a steps module or package loads a non-steps module or package. It is highly recommended to separate step definitions from broader logic.

  • Fresher allows duplicate function names for steps.

  • Fresher associates with a package the steps defined by all the modules that are its immediate children. Imagine the following structure:

    steps/
          __init__.py
          caret.py
          selection.py
          nested/
               __init__.py
               log.py
               data.py
    

    When this steps package is loaded by Fresher, all of the steps found in caret.py and selection.py will be immediately accessible. There is no need to refer to these modules individually or to add anything to the ``steps/__init__.py`` file. However, what is in the **subpackage named steps.nested will not be accessible until steps.nested is itself loaded by Fresher.

    With Freshen steps/__init__.py would require:

    from .caret import *
    from .selection import *
    

    but this is not required when using Fresher.

  • Generally speaking, the from ... import * method of making steps accessible in another module, which worked fine in Freshen, does not work in Fresher. It worked in Freshen because Freshen would determine the steps defined in a module by scanning the module's global symbols. This cannot work with Fresher because it allows duplicate function names. (If @given('a') and @given('b') both decorate foo() the symbol foo is still present only once.)

    You have to use fresher.stepregistry.import_steps() to import the steps from another module. For instance:

    from freshen.stepregistry import import_steps
    
    import_steps(".defs")
    

    Or if you want to import steps from a more remote location (actual case in the test suite):

    from freshen.stepregistry import import_steps
    
    import_steps("..nested.steps")
    

The old documentation follows. Keep in mind the differences above. Eventually, this will all be rewritten for Fresher.

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.

What's New in Version 0.2?

  • Freshen now supports Backgrounds for a feature.
  • Freshen now supports the But keyword for steps of Scenarios.
  • Freshen now supports the simple case of Step Argument Transforms.
  • The parser now supports several natural language aliases for a keyword.
  • If a natural language translation is not found for a keyword, English will be used.
  • "@After" hooks are now run in the opposite order of which they are registered.
  • Improved error handling and reporting.

There are also some modifications that are incompatible with Cucumber.

  • Only the step definition module named "steps" is used by default.
  • Users can override this behavior with the "Use step definitions from" keyword.
  • Freshen distinguishes "Given" steps from "When" steps and "Then" steps.

Freshen Documentation

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 (in this order):

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, Then, But or And. 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, substituting 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 substituted 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 substitute for).

Backgrounds

A feature may contain a background. It allows you to add some context to the scenarios in the current feature. A Background is much like a scenario containing a number of steps. The difference is when it is run. The background is run before each of your scenarios but after any of your "@Before" hooks.

Here is an example:

Feature: Befriending
  In order to have some friends
  As a Facebook user
  I want to be able to manage my list of friends

  Background:
    Given I am the user Ken
    And I have friends Barbie, Cloe

  Scenario: Adding a new friend
    When I add a new friend named Jade
    Then I should have friends Barbie, Cloe, Jade

  Scenario: Removing a friend
    When I remove my friend Cloe
    Then I should have friends Barbie

Note that background should be added in a feature only if it has a value for the client. Otherwise, you can use tagged hooks (see Tags and Hooks).

Step Definitions

When presented with a feature file, Freshen will execute each scenario. This involves iterating over each step in turn and 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 *

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.

Specifying Step Definition Modules

Step definitions are defined in python modules. By default, Freshen will try to load a module named "steps" from the same directory as the .feature file. If that is not the desired behavior, you can also explicitly specify which step definition modules to use for a feature. To do this, use the keyword Using step definitions from (or its abbreviation: Using steps) and specify which step definition modules you want to use. Each module name must be a quoted string and must be relative to the location of the feature file. You can specify one or more module names (they must be separated by commas).

Here is an example:

Using step definitions from: 'steps', 'step/page_steps'

Feature: Destroy a document
  In order to take out one's anger on a document
  As an unsatisfied reader
  I want to be able to rip off the pages of the document

  Scenario: Rip off a page
    Given a document of 5 pages
    And the page is 3
    When I rip off the current page
    Then the page is 3
    But the document has 4 pages

Although you have the opportunity to explicitly specify the step definition modules to use in Freshen, this is not a reason to fall into the Feature-Coupled Steps Antipattern!

A step definition module can import other step definition modules. When doing this, the actual step definition functions must be at the top level. For example:

from other_step_module import *

A step definition module can be a python package, as long as all the relevant functions are imported into __init__.py.

The python path will automatically include the current working directory and the directory of the .feature file.

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 of 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. They do not complain when a key is missing:

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

Running steps from within step definitions

You can call out to a step definition from within another step using the same notation used in feature files. To do this, use the run_steps function:

@Given('I do thing A')
def do_a():
    #Do something useful.
    pass

@Given('I have B')
def having_b():
    #Do something useful.
    pass

@Given('I do something that use both')
def use_both():
    run_steps("""
              Given I do thing A
              And I have B
              """)

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()

Step Argument Transforms

Step definitions are specified as regular expressions. Freshen will pass any captured sub-expressions (i.e. the parts in parentheses) to the step definition function as a string. However, it is often necessary to convert those strings into another type of object. For example, in the step:

Then user bob should be friends with user adelaide

we may need to convert "user bob" to the the object User(name='bob') and "user adelaide" to User(name="adelaide"). To do this repeatedly would break the "Do Not Repeat Yourself (DRY)" principle of good software development. Step Argument Transforms allow you to specify an automatic transformation for arguments if they match a certain regular expression. These transforms are created in the step definition file. For example:

@Transform(r"^user (\w+)$")
def transform_user(name):
    return User.objects.find(name)

@Then(r"^(user \w+) should be friends with (user \w+)")
def check_friends(user1, user2):
    # Here the arguments will already be User objects
    assert user1.is_friends_with(user2)

The two arguments to the "Then" step will be matched in the transform above and converted into a User object before being passed to the step definition.

Named Step Argument Transformation

Another imperfection of step definitions from the DRY perspective is that they require repeated regular expressions to read "the same thing". By keeping expressions extremely simple the damage can be minimized, but sometimes it can be useful to centralize the pattern specifications for certain argument types. Named Step Argument Transforms allow the use of a unique name a substitution point for the regular expression associated with a transform. For example, for the step:

Then these users should be friends: "bob, adelaide, samantha"

The following definitions can be used:

from itertools import combinations

 @NamedTransform( '{user list}', r'("[\w\, ]+")', r'^"([\w\, ]+)"$' )
 def transform_user_list( slist ):
    return [ User.objects.find( name )
             for name.strip() in slist.split( ',' ) ]

 @Then(r"these users should be friends: {user list}" )
 def check_all_friends( user_list ):
     for user1, user2 in combinations( user_list, 2 ):
         assert user1.is_friends_with( user2 )

The arguments to NamedTransform are name, in_pattern and out_pattern, respectively. NamedTranform is equivalent to having in_pattern substituted for all occurrences of name in step specifications, and defining a standard Transform with out_pattern as its pattern.

The distinction between in_pattern and out_pattern is that the in_pattern can be used to match surrounding context to uniquely identify parameters, while the out_pattern searches within the text recognized by the in_pattern to pull out the semantically relevant parts. When this distinction is not relevant, specify only one pattern, and it will be used for both in and out patterns.

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 not supported until plugin support is implemented. If you need to use Selenium, try version 0.1.

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.
  • --language: Run the tests using the designated language. See the Internationalization section for more details

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.

Internationalization

Freshen now supports 30 languages, exactly the same as cucumber, since the "language" file was borrowed from the cucumber project. As long as your .feature files respect the syntax, the person in charge of writing the acceptance tests may write it down in his/her mother tongue. The only exception is the new keyword for specifying step definition modules since it is not available in Cucumber. For the moment, this keyword is available only in English, French, and Portuguese. If you use another language, you must use the English keyword for this particular keyword (or translate it and add it to the languages.yml file).

The 'examples' directory contains a French sample. It's a simple translation of the English 'calc'. If you want to check the example, go to the 'calc_fr' directory, and run:

$ nosetests --with-freshen --language=fr

The default language is English.

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 re-implementing 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 repository and play around.

 
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