Sample environment generator

This is a tool to automate the generation of our sample environment
files.  It takes a yaml file as input, and based on the environments
defined in that file generates a number of sample environment files
from the parameters in the Heat templates.  A tox genconfig target
is added that mirrors how the other OpenStack services generate
their sample config files.

A description of the available options for the input file is
provided in a README file in the sample-env-generator directory.

In this commit only a single sample config is provided as a basic
example of how the tool works, but subsequent commits will add
more generated sample configs.

Change-Id: I855f33a61bba5337d844555a7c41b633b3327f7a
bp: environment-generator

.gitignore

@@ -22,8 +22,10 @@ lib64
 pip-log.txt
 
 # Unit test / coverage reports
+cover
 .coverage
 .tox
+.testrepository
 nosetests.xml
 
 # Translations

.testr.conf

@@ -0,0 +1,4 @@
+[DEFAULT]
+test_command=OS_STDOUT_CAPTURE=1 OS_STDERR_CAPTURE=1 OS_TEST_TIMEOUT=60 OS_LOG_CAPTURE=1 ${PYTHON:-python} -m subunit.run discover -t ./tripleo_heat_templates ./tripleo_heat_templates $LISTOPT $IDOPTION
+test_id_option=--load-list $IDFILE
+test_list_option=--list

environments/predictable-placement/custom-hostnames.yaml

@@ -0,0 +1,33 @@
+# *******************************************************************
+# This file was created automatically by the sample environment
+# generator. Developers should use `tox -e genconfig` to update it.
+# Users are recommended to make changes to a copy of the file instead
+# of the original, if any customizations are needed.
+# *******************************************************************
+# title: Custom Hostnames
+# description: |
+#   Hostname format for each role
+#   Note %index% is translated into the index of the node, e.g 0/1/2 etc
+#   and %stackname% is replaced with OS::stack_name in the template below.
+#   If you want to use the heat generated names, pass '' (empty string).
+parameter_defaults:
+  # Format for BlockStorage node hostnames Note %index% is translated into the index of the node, e.g 0/1/2 etc and %stackname% is replaced with the stack name e.g overcloud
+  # Type: string
+  BlockStorageHostnameFormat: '%stackname%-blockstorage-%index%'
+
+  # Format for CephStorage node hostnames Note %index% is translated into the index of the node, e.g 0/1/2 etc and %stackname% is replaced with the stack name e.g overcloud
+  # Type: string
+  CephStorageHostnameFormat: '%stackname%-cephstorage-%index%'
+
+  # Format for Compute node hostnames Note %index% is translated into the index of the node, e.g 0/1/2 etc and %stackname% is replaced with the stack name e.g overcloud
+  # Type: string
+  ComputeHostnameFormat: '%stackname%-novacompute-%index%'
+
+  # Format for Controller node hostnames Note %index% is translated into the index of the node, e.g 0/1/2 etc and %stackname% is replaced with the stack name e.g overcloud
+  # Type: string
+  ControllerHostnameFormat: '%stackname%-controller-%index%'
+
+  # Format for ObjectStorage node hostnames Note %index% is translated into the index of the node, e.g 0/1/2 etc and %stackname% is replaced with the stack name e.g overcloud
+  # Type: string
+  ObjectStorageHostnameFormat: '%stackname%-objectstorage-%index%'
+

sample-env-generator/README.rst

@@ -0,0 +1,149 @@
+Sample Environment Generator
+----------------------------
+
+This is a tool to automate the generation of our sample environment
+files.  It takes a yaml file as input, and based on the environments
+defined in that file generates a number of sample environment files
+from the parameters in the Heat templates.
+
+Usage
+=====
+
+The simplest case is when an existing sample environment needs to be
+updated to reflect changes in the templates.  Use the tox ``genconfig``
+target to do this::
+
+    tox -e genconfig
+
+.. note:: The tool should be run from the root directory of the
+          ``tripleo-heat-templates`` project.
+
+If a new sample environment is needed, it should be added to the
+``sample-env-generator/sample-environments.yaml`` file.  The existing
+entries in the file can be used as examples, and a more detailed
+explanation of the different available keys is below:
+
+- **name**: the output file will be this name + .yaml, in the
+  ``environments`` directory.
+- **title**: a human-readable title for the environment.
+- **description**: A description of the environment.  Will be included
+  as a comment at the top of the sample file.
+- **files**: The Heat templates containing the parameter definitions
+  for the environment.  Should be specified as a path relative to the
+  root of the ``tripleo-heat-templates`` project.  For example:
+  ``puppet/extraconfig/tls/tls-cert-inject.yaml:``.  Each filename
+  should be a YAML dictionary that contains a ``parameters`` entry.
+- **parameters**: There should be one ``parameters`` entry per file in the
+  ``files`` section (see the example configuration below).
+  This can be either a list of parameters related to
+  the environment, which is necessary for templates like
+  overcloud.yaml, or the string 'all', which indicates that all
+  parameters from the file should be included.
+- **static**: Can be used to specify that certain parameters must
+  not be changed.  Examples would be the EnableSomething params
+  in the templates.  When writing a sample config for Something,
+  ``EnableSomething: True`` would be a static param, since it
+  would be nonsense to include the environment with it set to any other
+  value.
+- **sample_values**: Sometimes it is useful to include a sample value
+  for a parameter that is not the parameter's actual default.
+  An example of this is the SSLCertificate param in the enable-tls
+  environment file.
+- **resource_registry**: Many environments also need to pass
+  resource_registry entries when they are used.  This can be used
+  to specify that in the configuration file.
+
+Some behavioral notes:
+
+- Parameters without default values will be marked as mandatory to indicate
+  that the user must set a value for them.
+- It is no longer recommended to set parameters using the ``parameters``
+  section.  Instead, all parameters should be set as ``parameter_defaults``
+  which will work regardless of whether the parameter is top-level or nested.
+  Therefore, the tool will always set parameters in the ``parameter_defaults``
+  section.
+- Parameters whose name begins with the _ character are treated as private.
+  This indicates that the parameter value will be passed in from another
+  template and does not need to be exposed directly to the user.
+
+If adding a new environment, don't forget to add the new file to the
+git repository so it will be included with the review.
+
+Example
+=======
+
+Given a Heat template named ``example.yaml`` that looks like::
+
+    parameters:
+      EnableExample:
+        default: False
+        description: Enable the example feature
+        type: boolean
+      ParamOne:
+        default: one
+        description: First example param
+        type: string
+      ParamTwo:
+        description: Second example param
+        type: number
+      _PrivateParam:
+        default: does not matter
+        description: Will not show up
+        type: string
+
+And an environment generator entry that looks like::
+
+    environments:
+      -
+        name: example
+        title: Example Environment
+        description: |
+          An example environment demonstrating how to use the sample
+          environment generator.  This text will be included at the top
+          of the generated file as a comment.
+        files:
+          example.yaml:
+            parameters: all
+        sample_values:
+          EnableExample: True
+        static:
+          - EnableExample
+        resource_registry:
+          OS::TripleO::ExampleData: ../extraconfig/example.yaml
+
+The generated environment file would look like::
+
+    # *******************************************************************
+    # This file was created automatically by the sample environment
+    # generator. Developers should use `tox -e genconfig` to update it.
+    # Users are recommended to make changes to a copy of the file instead
+    # of the original, if any customizations are needed.
+    # *******************************************************************
+    # title: Example Environment
+    # description: |
+    #   An example environment demonstrating how to use the sample
+    #   environment generator.  This text will be included at the top
+    #   of the generated file as a comment.
+    parameter_defaults:
+      # First example param
+      # Type: string
+      ParamOne: one
+
+      # Second example param
+      # Mandatory. This parameter must be set by the user.
+      # Type: number
+      ParamTwo: <None>
+
+      # ******************************************************
+      # Static parameters - these are values that must be
+      # included in the environment but should not be changed.
+      # ******************************************************
+      # Enable the example feature
+      # Type: boolean
+      EnableExample: True
+
+      # *********************
+      # End static parameters
+      # *********************
+    resource_registry:
+      OS::TripleO::ExampleData: ../extraconfig/example.yaml

sample-env-generator/sample-environments.yaml

@@ -0,0 +1,17 @@
+environments:
+  -
+    name: predictable-placement/custom-hostnames
+    title: Custom Hostnames
+    files:
+      overcloud.yaml:
+        parameters:
+          - ControllerHostnameFormat
+          - ComputeHostnameFormat
+          - BlockStorageHostnameFormat
+          - ObjectStorageHostnameFormat
+          - CephStorageHostnameFormat
+    description: |
+      Hostname format for each role
+      Note %index% is translated into the index of the node, e.g 0/1/2 etc
+      and %stackname% is replaced with OS::stack_name in the template below.
+      If you want to use the heat generated names, pass '' (empty string).

test-requirements.txt

@@ -7,3 +7,11 @@ six>=1.9.0 # MIT
 sphinx!=1.6.1,>=1.5.1 # BSD
 oslosphinx>=4.7.0 # Apache-2.0
 reno!=2.3.1,>=1.8.0 # Apache-2.0
+coverage>=4.0,!=4.4  # Apache-2.0
+fixtures>=3.0.0  # Apache-2.0/BSD
+python-subunit>=0.0.18  # Apache-2.0/BSD
+testrepository>=0.0.18  # Apache-2.0/BSD
+testscenarios>=0.4  # Apache-2.0/BSD
+testtools>=1.4.0  # MIT
+mock>=2.0  # BSD
+oslotest>=1.10.0  # Apache-2.0

tox.ini

@@ -1,12 +1,14 @@
 [tox]
 minversion = 1.6
 skipsdist = True
+envlist = py35,py27,pep8
 
 [testenv]
 usedevelop = True
 install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
+commands = python setup.py testr --slowest --testr-args='{posargs}'
 
 [testenv:venv]
 commands = {posargs}
@@ -22,3 +24,11 @@ commands = python ./tools/process-templates.py
 
 [testenv:releasenotes]
 commands = bash -c tools/releasenotes_tox.sh
+
+[testenv:cover]
+commands = python setup.py test --coverage --coverage-package-name=tripleo_heat_templates --testr-args='{posargs}'
+
+[testenv:genconfig]
+commands =
+           python ./tools/process-templates.py
+           python ./tripleo_heat_templates/environment_generator.py sample-env-generator/sample-environments.yaml

tripleo_heat_templates/environment_generator.py

@@ -0,0 +1,189 @@
+#!/usr/bin/env python
+
+# Copyright 2015 Red Hat Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import errno
+import os
+import sys
+import yaml
+
+
+_PARAM_FORMAT = u"""  # %(description)s
+  %(mandatory)s# Type: %(type)s
+  %(name)s: %(default)s
+"""
+_STATIC_MESSAGE_START = (
+    '  # ******************************************************\n'
+    '  # Static parameters - these are values that must be\n'
+    '  # included in the environment but should not be changed.\n'
+    '  # ******************************************************\n'
+    )
+_STATIC_MESSAGE_END = ('  # *********************\n'
+                       '  # End static parameters\n'
+                       '  # *********************\n'
+                       )
+_FILE_HEADER = (
+    '# *******************************************************************\n'
+    '# This file was created automatically by the sample environment\n'
+    '# generator. Developers should use `tox -e genconfig` to update it.\n'
+    '# Users are recommended to make changes to a copy of the file instead\n'
+    '# of the original, if any customizations are needed.\n'
+    '# *******************************************************************\n'
+    )
+# Certain parameter names can't be changed, but shouldn't be shown because
+# they are never intended for direct user input.
+_PRIVATE_OVERRIDES = ['server', 'servers', 'NodeIndex']
+
+
+def _create_output_dir(target_file):
+    try:
+        os.makedirs(os.path.dirname(target_file))
+    except OSError as e:
+        if e.errno == errno.EEXIST:
+            pass
+        else:
+            raise
+
+
+def _generate_environment(input_env, parent_env=None):
+    if parent_env is None:
+        parent_env = {}
+    env = dict(parent_env)
+    env.update(input_env)
+    parameter_defaults = {}
+    param_names = []
+    for template_file, template_data in env['files'].items():
+        with open(template_file) as f:
+            f_data = yaml.safe_load(f)
+            f_params = f_data['parameters']
+            parameter_defaults.update(f_params)
+            if template_data['parameters'] == 'all':
+                new_names = [k for k, v in f_params.items()]
+            else:
+                new_names = template_data['parameters']
+            missing_params = [name for name in new_names
+                              if name not in f_params]
+            if missing_params:
+                raise RuntimeError('Did not find specified parameter names %s '
+                                   'in file %s for environment %s' %
+                                   (missing_params, template_file,
+                                    env['name']))
+            param_names += new_names
+
+    static_names = env.get('static', [])
+    static_defaults = {k: v for k, v in parameter_defaults.items()
+                       if k in param_names and
+                       k in static_names
+                       }
+    parameter_defaults = {k: v for k, v in parameter_defaults.items()
+                          if k in param_names and
+                          k not in _PRIVATE_OVERRIDES and
+                          not k.startswith('_') and
+                          k not in static_names
+                          }
+    for k, v in env.get('sample_values', {}).items():
+        if k in parameter_defaults:
+            parameter_defaults[k]['sample'] = v
+        if k in static_defaults:
+            static_defaults[k]['sample'] = v
+
+    def write_sample_entry(f, name, value):
+        default = value.get('default')
+        mandatory = ''
+        if default is None:
+            mandatory = ('# Mandatory. This parameter must be set by the '
+                         'user.\n  ')
+            default = '<None>'
+        if value.get('sample') is not None:
+            default = value['sample']
+        if default == '':
+            default = "''"
+        try:
+            # If the default value is something like %index%, yaml won't
+            # parse the output correctly unless we wrap it in quotes.
+            # However, not all default values can be wrapped so we need to
+            # do it conditionally.
+            if default.startswith('%'):
+                default = "'%s'" % default
+        except AttributeError:
+            pass
+
+        values = {'name': name,
+                  'type': value['type'],
+                  'description':
+                      value.get('description', '').rstrip().replace('\n',
+                                                                    '\n  # '),
+                  'default': default,
+                  'mandatory': mandatory,
+                  }
+        f.write(_PARAM_FORMAT % values + '\n')
+
+    target_file = os.path.join('environments', env['name'] + '.yaml')
+    _create_output_dir(target_file)
+    with open(target_file, 'w') as env_file:
+        env_file.write(_FILE_HEADER)
+        # TODO(bnemec): Once Heat allows the title and description to live in
+        # the environment itself, uncomment these entries and make them
+        # top-level keys in the YAML.
+        env_title = env.get('title', '')
+        env_file.write(u'# title: %s\n' % env_title)
+        env_desc = env.get('description', '')
+        env_file.write(u'# description: |\n')
+        for line in env_desc.splitlines():
+            env_file.write(u'#   %s\n' % line)
+
+        if parameter_defaults:
+            env_file.write(u'parameter_defaults:\n')
+        for name, value in sorted(parameter_defaults.items()):
+            write_sample_entry(env_file, name, value)
+        if static_defaults:
+            env_file.write(_STATIC_MESSAGE_START)
+        for name, value in sorted(static_defaults.items()):
+            write_sample_entry(env_file, name, value)
+        if static_defaults:
+            env_file.write(_STATIC_MESSAGE_END)
+
+        if env.get('resource_registry'):
+            env_file.write(u'resource_registry:\n')
+        for res, value in sorted(env.get('resource_registry', {}).items()):
+            env_file.write(u'  %s: %s\n' % (res, value))
+        print('Wrote sample environment "%s"' % target_file)
+
+    for e in env.get('children', []):
+        _generate_environment(e, env)
+
+
+def generate_environments(config_file):
+    with open(config_file) as f:
+        config = yaml.safe_load(f)
+    for env in config['environments']:
+        _generate_environment(env)
+
+
+def usage(exit_code=1):
+    print('Usage: %s <filename.yaml>' % sys.argv[0])
+    sys.exit(exit_code)
+
+
+def main():
+    try:
+        config_file = sys.argv[1]
+    except IndexError:
+        usage()
+    generate_environments(config_file)
+
+
+if __name__ == '__main__':
+    main()

tripleo_heat_templates/tests/test_environment_generator.py

@@ -0,0 +1,396 @@
+# Copyright 2015 Red Hat Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import io
+import tempfile
+
+import mock
+from oslotest import base
+import six
+import testscenarios
+
+from tripleo_heat_templates import environment_generator
+
+load_tests = testscenarios.load_tests_apply_scenarios
+
+basic_template = '''
+parameters:
+  FooParam:
+    default: foo
+    description: Foo description
+    type: string
+  BarParam:
+    default: 42
+    description: Bar description
+    type: number
+resources:
+  # None
+'''
+basic_private_template = '''
+parameters:
+  FooParam:
+    default: foo
+    description: Foo description
+    type: string
+  _BarParam:
+    default: 42
+    description: Bar description
+    type: number
+resources:
+  # None
+'''
+mandatory_template = '''
+parameters:
+  FooParam:
+    description: Mandatory param
+    type: string
+resources:
+  # None
+'''
+index_template = '''
+parameters:
+  FooParam:
+    description: Param with %index% as its default
+    type: string
+    default: '%index%'
+resources:
+  # None
+'''
+multiline_template = '''
+parameters:
+  FooParam:
+    description: |
+      Parameter with
+      multi-line description
+    type: string
+    default: ''
+resources:
+  # None
+'''
+
+
+class GeneratorTestCase(base.BaseTestCase):
+    content_scenarios = [
+        ('basic',
+         {'template': basic_template,
+          'exception': None,
+          'input_file': '''environments:
+  -
+    name: basic
+    title: Basic Environment
+    description: Basic description
+    files:
+      foo.yaml:
+        parameters: all
+''',
+          'expected_output': '''# title: Basic Environment
+# description: |
+#   Basic description
+parameter_defaults:
+  # Bar description
+  # Type: number
+  BarParam: 42
+
+  # Foo description
+  # Type: string
+  FooParam: foo
+
+''',
+          }),
+        ('basic-one-param',
+         {'template': basic_template,
+          'exception': None,
+          'input_file': '''environments:
+  -
+    name: basic
+    title: Basic Environment
+    description: Basic description
+    files:
+      foo.yaml:
+        parameters:
+          - FooParam
+''',
+          'expected_output': '''# title: Basic Environment
+# description: |
+#   Basic description
+parameter_defaults:
+  # Foo description
+  # Type: string
+  FooParam: foo
+
+''',
+          }),
+        ('basic-static-param',
+         {'template': basic_template,
+          'exception': None,
+          'input_file': '''environments:
+  -
+    name: basic
+    title: Basic Environment
+    description: Basic description
+    files:
+      foo.yaml:
+        parameters: all
+    static:
+      - BarParam
+''',
+          'expected_output': '''# title: Basic Environment
+# description: |
+#   Basic description
+parameter_defaults:
+  # Foo description
+  # Type: string
+  FooParam: foo
+
+  # ******************************************************
+  # Static parameters - these are values that must be
+  # included in the environment but should not be changed.
+  # ******************************************************
+  # Bar description
+  # Type: number
+  BarParam: 42
+
+  # *********************
+  # End static parameters
+  # *********************
+''',
+          }),
+        ('basic-static-param-sample',
+         {'template': basic_template,
+          'exception': None,
+          'input_file': '''environments:
+  -
+    name: basic
+    title: Basic Environment
+    description: Basic description
+    files:
+      foo.yaml:
+        parameters: all
+    static:
+      - BarParam
+    sample_values:
+      BarParam: 1
+      FooParam: ''
+''',
+          'expected_output': '''# title: Basic Environment
+# description: |
+#   Basic description
+parameter_defaults:
+  # Foo description
+  # Type: string
+  FooParam: ''
+
+  # ******************************************************
+  # Static parameters - these are values that must be
+  # included in the environment but should not be changed.
+  # ******************************************************
+  # Bar description
+  # Type: number
+  BarParam: 1
+
+  # *********************
+  # End static parameters
+  # *********************
+''',
+          }),
+        ('basic-private',
+         {'template': basic_private_template,
+          'exception': None,
+          'input_file': '''environments:
+  -
+    name: basic
+    title: Basic Environment
+    description: Basic description
+    files:
+      foo.yaml:
+        parameters: all
+''',
+          'expected_output': '''# title: Basic Environment
+# description: |
+#   Basic description
+parameter_defaults:
+  # Foo description
+  # Type: string
+  FooParam: foo
+
+''',
+          }),
+        ('mandatory',
+         {'template': mandatory_template,
+          'exception': None,
+          'input_file': '''environments:
+  -
+    name: basic
+    title: Basic Environment
+    description: Basic description
+    files:
+      foo.yaml:
+        parameters: all
+''',
+          'expected_output': '''# title: Basic Environment
+# description: |
+#   Basic description
+parameter_defaults:
+  # Mandatory param
+  # Mandatory. This parameter must be set by the user.
+  # Type: string
+  FooParam: <None>
+
+''',
+          }),
+        ('basic-sample',
+         {'template': basic_template,
+          'exception': None,
+          'input_file': '''environments:
+  -
+    name: basic
+    title: Basic Environment
+    description: Basic description
+    files:
+      foo.yaml:
+        parameters: all
+    sample_values:
+      FooParam: baz
+''',
+          'expected_output': '''# title: Basic Environment
+# description: |
+#   Basic description
+parameter_defaults:
+  # Bar description
+  # Type: number
+  BarParam: 42
+
+  # Foo description
+  # Type: string
+  FooParam: baz
+
+''',
+          }),
+        ('basic-resource-registry',
+         {'template': basic_template,
+          'exception': None,
+          'input_file': '''environments:
+  -
+    name: basic
+    title: Basic Environment
+    description: Basic description
+    files:
+      foo.yaml:
+        parameters: all
+    resource_registry:
+      OS::TripleO::FakeResource: fake-filename.yaml
+''',
+          'expected_output': '''# title: Basic Environment
+# description: |
+#   Basic description
+parameter_defaults:
+  # Bar description
+  # Type: number
+  BarParam: 42
+
+  # Foo description
+  # Type: string
+  FooParam: foo
+
+resource_registry:
+  OS::TripleO::FakeResource: fake-filename.yaml
+''',
+          }),
+        ('missing-param',
+         {'template': basic_template,
+          'exception': RuntimeError,
+          'input_file': '''environments:
+  -
+    name: basic
+    title: Basic Environment
+    description: Basic description
+    files:
+      foo.yaml:
+        parameters:
+          - SomethingNonexistent
+''',
+          'expected_output': None,
+          }),
+        ('percent-index',
+         {'template': index_template,
+          'exception': None,
+          'input_file': '''environments:
+  -
+    name: basic
+    title: Basic Environment
+    description: Basic description
+    files:
+      foo.yaml:
+        parameters: all
+''',
+          'expected_output': '''# title: Basic Environment
+# description: |
+#   Basic description
+parameter_defaults:
+  # Param with %index% as its default
+  # Type: string
+  FooParam: '%index%'
+
+''',
+          }),
+        ('multi-line-desc',
+         {'template': multiline_template,
+          'exception': None,
+          'input_file': '''environments:
+  -
+    name: basic
+    title: Basic Environment
+    description: Basic description
+    files:
+      foo.yaml:
+        parameters: all
+''',
+          'expected_output': '''# title: Basic Environment
+# description: |
+#   Basic description
+parameter_defaults:
+  # Parameter with
+  # multi-line description
+  # Type: string
+  FooParam: ''
+
+''',
+          }),
+        ]
+
+    @classmethod
+    def generate_scenarios(cls):
+        cls.scenarios = testscenarios.multiply_scenarios(
+            cls.content_scenarios)
+
+    def test_generator(self):
+        fake_input = io.StringIO(six.text_type(self.input_file))
+        fake_template = io.StringIO(six.text_type(self.template))
+        _, fake_output_path = tempfile.mkstemp()
+        fake_output = open(fake_output_path, 'w')
+        with mock.patch('tripleo_heat_templates.environment_generator.open',
+                        create=True) as mock_open:
+            mock_open.side_effect = [fake_input, fake_template, fake_output]
+            if not self.exception:
+                environment_generator.generate_environments('ignored.yaml')
+            else:
+                self.assertRaises(self.exception,
+                                  environment_generator.generate_environments,
+                                  'ignored.yaml')
+                return
+        expected = environment_generator._FILE_HEADER + self.expected_output
+        with open(fake_output_path) as f:
+            self.assertEqual(expected, f.read())
+
+GeneratorTestCase.generate_scenarios()