YamlTestDirGenerator (#606)

Import the class and documentation from stacker_blueprints.

docs/blueprints.rst

@@ -411,3 +411,33 @@ stacker_blueprints repo. For example, see the tests used to test the
 .. _output results: https://github.com/cloudtools/stacker_blueprints/tree/master/tests/fixtures/blueprints
 .. _Resource Type: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-template-resource-type-ref.html
 .. _Property Type: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-product-property-reference.html
+
+Yaml (stacker) format tests
+---------------------------
+
+In order to wrap the `BlueprintTestCase` tests in a format similar to stacker's
+stack format, the `YamlDirTestGenerator` class is provided. When subclassed in
+a directory, it will search for yaml files in that directory with certain
+structure and execute a test case for it. As an example:
+
+.. code-block:: yaml
+  ---
+  namespace: test
+  stacks:
+    - name: test_stack
+      class_path: stacker_blueprints.s3.Buckets
+      variables:
+        var1: val1
+
+When run from nosetests, this will create a template fixture file called
+test_stack.json containing the output from the `stacker_blueprints.s3.Buckets`
+template.
+
+Examples of using the `YamlDirTestGenerator` class can be found in the
+stacker_blueprints repo. For example, see the tests used to test the
+`s3.Buckets`_ class and the accompanying `fixture`_. These are
+generated from a `subclass of YamlDirTestGenerator`_.
+
+.. _s3.Buckets: https://github.com/cloudtools/stacker_blueprints/blob/yaml-tests/tests/test_s3.yaml
+.. _fixture: https://github.com/cloudtools/stacker_blueprints/tree/yaml-tests/tests/fixtures/blueprints/s3_static_website.json
+.. _subclass of YamlDirTestGenerator: https://github.com/cloudtools/stacker_blueprints/tree/yaml-tests/tests/__init__.py

stacker/blueprints/testutil.py

@@ -1,6 +1,13 @@
 import difflib
 import json
 import unittest
+import os.path
+from glob import glob
+
+from stacker.config import parse as parse_config
+from stacker.context import Context
+from stacker.util import load_object_from_string
+from stacker.variables import Variable
 
 
 def diff(a, b):
@@ -33,3 +40,118 @@ def assertRenderedBlueprint(self, blueprint):  # noqa: N802
 
         self.assertEquals(rendered_dict, expected_dict,
                           diff(rendered_text, expected_text))
+
+
+class YamlDirTestGenerator(object):
+    """Generate blueprint tests from yaml config files.
+
+    This class creates blueprint tests from yaml files with a syntax similar to
+    stackers' configuration syntax. For example,
+
+       ---
+       namespace: test
+       stacks:
+         - name: test_sample
+           class_path: stacker_blueprints.test.Sample
+           variables:
+             var1: value1
+
+    will create a test for the specified blueprint, passing that variable as
+    part of the test.
+
+    The test will generate a .json file for this blueprint, and compare it with
+    the stored result.
+
+
+    By default, the generator looks for files named 'test_*.yaml' in its same
+    directory. In order to use it, subclass it in a directory containing such
+    tests, and name the class with a pattern that will include it in nosetests'
+    tests (for example, TestGenerator).
+
+    The subclass may override some properties:
+
+    @property base_class: by default, the generated tests are subclasses of
+    stacker.blueprints.testutil.BlueprintTestCase. In order to change this,
+    set this property to the desired base class.
+
+    @property yaml_dirs: by default, the directory where the generator is
+    subclassed is searched for test files. Override this array for specifying
+    more directories. These must be relative to the directory in which the
+    subclass lives in. Globs may be used.
+        Default: [ '.' ]. Example override: [ '.', 'tests/*/' ]
+
+    @property yaml_filename: by default, the generator looks for files named
+    'test_*.yaml'. Use this to change this pattern. Globs may be used.
+
+
+    There's an example of this use in the tests/ subdir of stacker_blueprints.
+
+    """
+
+    def __init__(self):
+        self.classdir = os.path.relpath(
+            self.__class__.__module__.replace('.', '/'))
+        if not os.path.isdir(self.classdir):
+            self.classdir = os.path.dirname(self.classdir)
+
+    # These properties can be overriden from the test generator subclass.
+    @property
+    def base_class(self):
+        return BlueprintTestCase
+
+    @property
+    def yaml_dirs(self):
+        return ['.']
+
+    @property
+    def yaml_filename(self):
+        return 'test_*.yaml'
+
+    def test_generator(self):
+        # Search for tests in given paths
+        configs = []
+        for d in self.yaml_dirs:
+            configs.extend(
+                glob('%s/%s/%s' % (self.classdir, d, self.yaml_filename)))
+
+        class ConfigTest(self.base_class):
+            def __init__(self, config, stack, filepath):
+                self.config = config
+                self.stack = stack
+                self.description = "%s (%s)" % (stack.name, filepath)
+
+            def __call__(self):
+                # Use the context property of the baseclass, if present.
+                # If not, default to a basic context.
+                try:
+                    ctx = self.context
+                except AttributeError:
+                    ctx = Context(config=self.config,
+                                  environment={'environment': 'test'})
+
+                configvars = self.stack.variables or {}
+                variables = [Variable(k, v) for k, v in configvars.iteritems()]
+
+                blueprint_class = load_object_from_string(
+                    self.stack.class_path)
+                blueprint = blueprint_class(self.stack.name, ctx)
+                blueprint.resolve_variables(variables or [])
+                blueprint.setup_parameters()
+                blueprint.create_template()
+                self.assertRenderedBlueprint(blueprint)
+
+            def assertEquals(self, a, b, msg):  # noqa: N802
+                assert a == b, msg
+
+        for f in configs:
+            with open(f) as test:
+                config = parse_config(test.read())
+                config.validate()
+
+                for stack in config.stacks:
+                    # Nosetests supports "test generators", which allows us to
+                    # yield a callable object which will be wrapped as a test
+                    # case.
+                    #
+                    # http://nose.readthedocs.io/en/latest/writing_tests.html#test-generators
+                    yield ConfigTest(config, stack, filepath=f)