chore: Add contributing file and tox setup'

.travis.yml

@@ -0,0 +1,39 @@
+language: python
+
+# Required for Python 3.7+.
+#   See: https://github.com/travis-ci/travis-ci/issues/9069#issuecomment-425720905
+dist: xenial
+
+matrix:
+    include:
+        - python: 3.2
+          env: TOXENV=py32
+        - python: 3.3
+          env: TOXENV=py33
+        - python: 3.4
+          env: TOXENV=py34
+        - python: 3.5
+          env: TOXENV=py35
+        - python: 3.6
+          env: TOXENV=py36
+        - python: 3.7
+          env: TOXENV=py37
+        - python: 3.8
+          env: TOXENV=py38
+        - python: 3.8
+          env: TOXENV=pep8
+        - python: 3.8
+          env: TOXENV=mypy
+        - python: 3.8
+          env: TOXENV=docs
+
+install:
+  # Ensure virtualenv is up to date to avoid DeprecationWarning in bundled site.py.
+  - pip install --upgrade virtualenv
+  - pip install tox
+
+script:
+  tox
+
+after_success:
+  - coveralls

CONTRIBUTING.md

@@ -0,0 +1,289 @@
+Contributing
+=============
+
+This guidelines exposes to any contributor how install the development enviroment, the project architecture and code style.
+
+Requirements
+------------
+
+Python 3.2+.
+
+> **note**
+>
+> Because [Python 2.7 supports ended January 1,
+> 2020](https://pythonclock.org/), new projects should consider
+> supporting Python 3 only, which is simpler than trying to support
+> both. As a result, support for Python 2.7 in this example project has
+> been dropped.
+
+Windows Support
+---------------
+
+Summary: On Windows, use `py` instead of `python3` for many of the
+examples in this documentation.
+
+This package fully supports Windows, along with Linux and macOS, but
+Python is typically [installed differently on
+Windows](https://docs.python.org/3/using/windows.html). Windows users
+typically access Python through the
+[py](https://www.python.org/dev/peps/pep-0397/) launcher rather than a
+`python3` link in their `PATH`. Within a virtual environment, all
+platforms operate the same and use a `python` link to access the Python
+version used in that virtual environment.
+
+Installation
+------------
+
+To install and run the program without development environment folloe
+the instruction
+
+Create and start the virtual environment (Check section "Virtual
+Environments" for more details) 
+
+```bash
+$ python3 -m venv venv
+
+$ source venv/bin/activate
+```
+
+Install the requirements
+
+```bash
+$ pip install -r requirements.txt
+```
+
+To execute the cli (example)
+
+
+Packaging
+---------
+
+This project is designed as a Python package, meaning that it can be
+bundled up and redistributed as a single compressed file.
+
+Packaging is configured by:
+
+-   `setup.py`
+-   `MANIFEST.in`
+
+### Source Distribution
+
+To package the project as a [source
+distribution](https://docs.python.org/3/distutils/sourcedist.html):
+
+``` bash
+$ python3 setup.py sdist
+```
+
+This will generate `dist/cryptosteganography-0.0.1.tar.gz`.
+
+Dependencies
+------------
+
+Dependencies are defined in:
+
+-   `requirements.in`
+-   `requirements.txt`
+-   `dev-requirements.in`
+-   `dev-requirements.txt`
+
+### Virtual Environments
+
+It is best practice during development to create an isolated [Python
+virtual environment](https://docs.python.org/3/library/venv.html) using
+the `venv` standard library module. This will keep dependant Python
+packages from interfering with other Python projects on your system.
+
+On \*Nix:
+
+``` {.sourceCode .bash}
+$ python3 -m venv venv
+$ source venv/bin/activate
+```
+
+On Windows `cmd`:
+
+``` bash
+> py -m venv venv
+> venv\Scripts\activate.bat
+```
+
+Once activated, it is good practice to update `pip` to the latest
+version.
+
+``` bash
+(venv) $ pip install --upgrade pip
+```
+
+### (Applications Only) Locking Dependencies
+
+This project uses [pip-tools](https://github.com/jazzband/pip-tools) to
+lock project dependencies and create reproducible virtual environments.
+
+**Note:** *Library* projects should not lock their `requirements.txt`.
+Since `python-blueprint` also has a CLI application, this end-user
+application example is used to demonstrate how to lock application
+dependencies.
+
+To update dependencies:
+
+``` bash
+(venv) $ pip install pip-tools
+(venv) $ pip-compile --upgrade
+(venv) $ pip-compile --upgrade dev-requirements.in
+```
+
+After upgrading dependencies, run the unit tests as described in the
+Unit Testing\_ section to ensure that none of the updated packages
+caused incompatibilities in the current project.
+
+### Syncing Virtual Environments
+
+To cleanly install your dependencies into your virtual environment:
+
+``` bash
+(venv) $ pip-sync requirements.txt dev-requirements.txt
+```
+
+Testing
+-------
+
+Automated testing is performed using
+[tox](https://tox.readthedocs.io/en/latest/index.html). tox will
+automatically create virtual environments based on `tox.ini` for unit
+testing, PEP8 style guide checking, and documentation generation.
+
+``` {.sourceCode .bash}
+# Install tox (only needed once).
+$ python3 -m pip install tox
+
+# Run all environments.
+#   To only run a single environment, specify it like: -e pep8
+$ tox
+```
+
+### Unit Testing
+
+Unit testing is performed with [pytest](https://pytest.org/). pytest has
+become the defacto Python unit testing framework. Some key advantages
+over the built in
+[unittest](https://docs.python.org/3/library/unittest.html) module are:
+
+1.  Significantly less boilerplate needed for tests.
+2.  PEP8 compliant names (e.g. `pytest.raises()` instead of
+    `self.assertRaises()`).
+3.  Vibrant ecosystem of plugins.
+
+pytest will automatically discover and run tests by recursively
+searching for folders and `.py` files prefixed with `test` for any
+functions prefixed by `test`.
+
+The `tests` folder is created as a Python package (i.e. there is an
+`__init__.py` file within it) because this helps `pytest` uniquely
+namespace the test files. Without this, two test files cannot be named
+the same, even if they are in different sub-directories.
+
+Code coverage is provided by the
+[pytest-cov](https://pytest-cov.readthedocs.io/en/latest/) plugin.
+
+When running a unit test tox environment (e.g. `tox`, `tox -e py37`,
+etc.), a data file (e.g. `.coverage.py37`) containing the coverage data
+is generated. This file is not readable on its own, but when the
+`coverage` tox environment is run (e.g. `tox` or `tox -e -coverage`),
+coverage from all unit test environments is combined into a single data
+file and an HTML report is generated in the `htmlcov` folder showing
+each source file and which lines were executed during unit testing. Open
+`htmlcov/index.html` in a web browser to view the report. Code coverage
+reports help identify areas of the project that are currently not
+tested.
+
+Code coverage is configured in the `.coveragerc` file.
+
+### Code Style Checking
+
+[PEP8](https://www.python.org/dev/peps/pep-0008/) is the universally
+accepted style guide for Python code. PEP8 code compliance is verified
+using [flake8](http://flake8.pycqa.org/). flake8 is configured in the
+`[flake8]` section of `tox.ini`. Three extra flake8 plugins are also
+included:
+
+-   `pep8-naming`: Ensure functions, classes, and variables are named
+    with correct casing.
+-   `flake8-quotes`: Ensure that `' '` style string quoting is used
+    consistently.
+-   `flake8-import-order`: Ensure consistency in the way imports are
+    grouped and sorted.
+
+Project Structure
+-----------------
+
+Traditionally, Python projects place the source for their packages in
+the root of the project structure, like:
+
+``` {.sourceCode .}
+root_folder
+├── cryptosteganography
+│   ├── __init__.py
+│   ├── cli.py
+│   └── lib.py
+├── tests
+│   ├── __init__.py
+│   └── test_generate.py
+├── tox.ini
+└── setup.py
+```
+
+However, this structure is
+[known](https://docs.pytest.org/en/latest/goodpractices.html#tests-outside-application-code)
+to have bad interactions with `pytest` and `tox`, two standard tools
+maintaining Python projects. The fundamental issue is that tox creates
+an isolated virtual environment for testing. By installing the
+distribution into the virtual environment, `tox` ensures that the tests
+pass even after the distribution has been packaged and installed,
+thereby catching any errors in packaging and installation scripts, which
+are common. Having the Python packages in the project root subverts this
+isolation for two reasons:
+
+1.  Calling `python` in the project root (for example,
+    `python -m pytest tests/`) [causes Python to add the current working
+    directory](https://docs.pytest.org/en/latest/pythonpath.html#invoking-pytest-versus-python-m-pytest)
+    (the project root) to `sys.path`, which Python uses to find modules.
+    Because the source package `cryptosteganography` is in the project root, it
+    shadows the `cryptosteganography` package installed in the tox environment.
+2.  Calling `pytest` directly anywhere that it can find the tests will
+    also add the project root to `sys.path` if the `tests` folder is a a
+    Python package (that is, it contains a `__init__.py` file). [pytest
+    adds all folders containing
+    packages](https://docs.pytest.org/en/latest/goodpractices.html#conventions-for-python-test-discovery)
+    to `sys.path` because it imports the tests like regular Python
+    modules.
+
+In order to properly test the project, the source packages must not be
+on the Python path. To prevent this, there are three possible solutions:
+
+1.  Remove the `__init__.py` file from `tests` and run `pytest` directly
+    as a tox command.
+2.  Remove the `__init__.py` file from tests and change the working
+    directory of `python -m pytest` to `tests`.
+3.  Move the source packages to a dedicated `src` folder.
+
+The dedicated `src` directory is the [recommended
+solution](https://docs.pytest.org/en/latest/pythonpath.html#test-modules-conftest-py-files-inside-packages)
+by `pytest` when using tox and the solution this blueprint promotes
+because it is the least brittle even though it deviates from the
+traditional Python project structure. It results is a directory
+structure like:
+
+``` {.sourceCode .}
+root_folder
+├── src
+│   └── cryptosteganography
+│       ├── __init__.py
+│       ├── cli.py
+│       └── lib.py
+├── tests
+│   ├── __init__.py
+│   └── test_generate.py
+├── tox.ini
+└── setup.py
+```

setup.py

@@ -50,6 +50,9 @@ def readme():
         'Programming Language :: Python',
         'Programming Language :: Python :: 3',
         'Programming Language :: Python :: 3 :: Only',
+        'Programming Language :: Python :: 3.2',
+        'Programming Language :: Python :: 3.3',
+        'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',