Make sure the bootstrap script actually works::

    >>> import os, sys
    >>> from os.path import dirname, join
    >>> import zc.buildout
    >>> bootstrap_py = join(
    ...    dirname(
    ...     dirname(
    ...      dirname(
    ...       dirname(zc.buildout.__file__)
    ...        )
    ...      )
    ...    ),
    ...   'bootstrap', 'bootstrap.py')
    >>> sample_buildout = tmpdir('sample')
    >>> os.chdir(sample_buildout)
    >>> write('buildout.cfg',
    ... '''
    ... [buildout]
    ... parts =
    ... ''')
    >>> write('bootstrap.py', open(bootstrap_py).read())
    >>> print_('X'); print_(system(
    ...     zc.buildout.easy_install._safe_arg(sys.executable)+' '+
    ...     'bootstrap.py')); print_('X') # doctest: +ELLIPSIS
    X...
    Creating directory '/sample/bin'.
    Creating directory '/sample/parts'.
    Creating directory '/sample/eggs'.
    Creating directory '/sample/develop-eggs'.
    Generated script '/sample/bin/buildout'.
    ...

    >>> ls(sample_buildout)
    d  bin
    -  bootstrap.py
    -  buildout.cfg
    d  develop-eggs
    d  eggs
    d  parts


    >>> ls(sample_buildout, 'bin')
    -  buildout

    >>> print_('X'); ls(sample_buildout, 'eggs') # doctest: +ELLIPSIS
    X...
    d  zc.buildout-...egg

By default it gets the latest version:

    >>> buildout_script = join(sample_buildout, 'bin', 'buildout')
    >>> if sys.platform.startswith('win'):
    ...     buildout_script += '-script.py'
    >>> print_(open(buildout_script).read()) # doctest: +ELLIPSIS
    #...
    sys.path[0:0] = [
      '/sample/eggs/setuptools-...egg',
      '/sample/eggs/zc.buildout-22.0.0...egg',
      ]...

Now trying the `--version` option, that let you define a version for
`zc.buildout`.

Let's try with an unknown version::

    >>> print_('X'); print_(system(
    ...     zc.buildout.easy_install._safe_arg(sys.executable)+' '+
    ...     'bootstrap.py --version UNKNOWN')); print_('X') # doctest: +ELLIPSIS
    ...
    X
    ...
    No local packages or download links found for zc.buildout==UNKNOWN
    ...

Now let's try with `2.0.0`, which happens to exist::

    >>> print_('X'); print_(system(
    ...     zc.buildout.easy_install._safe_arg(sys.executable)+' '+
    ...     'bootstrap.py --version 2.0.0')); print_('X')
    ... # doctest: +ELLIPSIS
    X...Generated script '/sample/bin/buildout'...X

Let's make sure the generated `buildout` script uses it::

    >>> print_(open(buildout_script).read()) # doctest: +ELLIPSIS
    #...
    sys.path[0:0] = [
      '/sample/eggs/setuptools-...egg',
      '/sample/eggs/zc.buildout-2.0.0...egg',
      ]...
