--- a/tests/conftest.py	Wed Apr 15 16:38:55 2015 -0700
+++ b/tests/conftest.py	Wed Apr 15 16:39:35 2015 -0700
@@ -1,5 +1,11 @@
 import sys
+import pprint
+import os.path
 import logging
+import pytest
+import yaml
+from piecrust.configuration import merge_dicts
+from .mockutil import mock_fs, mock_fs_scope
 
 
 def pytest_runtest_setup(item):
@@ -7,7 +13,9 @@
 
 
 def pytest_addoption(parser):
-    parser.addoption('--log-debug', action='store_true',
+    parser.addoption(
+            '--log-debug',
+            action='store_true',
             help="Sets the PieCrust logger to output debug info to stdout.")
 
 
@@ -17,3 +25,160 @@
         logging.getLogger('piecrust').addHandler(hdl)
         logging.getLogger('piecrust').setLevel(logging.DEBUG)
 
+
+def pytest_collect_file(parent, path):
+    if path.ext == ".bake" and path.basename.startswith("test"):
+        return BakeTestFile(path, parent)
+
+
+class BakeTestFile(pytest.File):
+    def collect(self):
+        spec = yaml.load_all(self.fspath.open())
+        for i, item in enumerate(spec):
+            name = '%s_%d' % (self.fspath.basename, i)
+            if 'test_name' in item:
+                name += '_%s' % item['test_name']
+            yield BakeTestItem(name, self, item)
+
+
+class BakeTestItem(pytest.Item):
+    def __init__(self, name, parent, spec):
+        super(BakeTestItem, self).__init__(name, parent)
+        self.spec = spec
+
+    def runtest(self):
+        fs = mock_fs()
+
+        # Website config.
+        config = {
+                'site': {
+                    'default_format': 'none',
+                    'default_page_layout': 'none',
+                    'default_post_layout': 'none'}
+                }
+        test_config = self.spec.get('config')
+        if test_config is not None:
+            merge_dicts(config, test_config)
+        fs.withConfig(config)
+
+        # Input file-system.
+        input_files = self.spec.get('in')
+        if input_files is not None:
+            _add_mock_files(fs, '/kitchen', input_files)
+
+        # Output file-system.
+        expected_output_files = self.spec.get('out')
+        expected_partial_files = self.spec.get('outfiles')
+
+        # Bake!
+        from piecrust.baking.baker import Baker
+        with mock_fs_scope(fs):
+            out_dir = fs.path('kitchen/_counter')
+            app = fs.getApp()
+            baker = Baker(app, out_dir)
+            baker.bake()
+
+        if expected_output_files:
+            actual = fs.getStructure('kitchen/_counter')
+            error = _compare_dicts(actual, expected_output_files)
+            if error:
+                raise ExpectedBakeOutputError(error)
+
+        if expected_partial_files:
+            for key, content in expected_partial_files.items():
+                try:
+                    actual = fs.getStructure('kitchen/_counter/' +
+                                             key.lstrip('/'))
+                except Exception:
+                    raise ExpectedBakeOutputError([
+                        "Missing expected output file: %s" % key])
+                if not isinstance(actual, str):
+                    raise ExpectedBakeOutputError([
+                        "Expected output file is a directory: %s" % key])
+                if actual != content:
+                    raise ExpectedBakeOutputError([
+                        "Unexpected output file contents:",
+                        "%s: %s" % (key, content),
+                        "%s: %s" % (key, actual)])
+
+    def reportinfo(self):
+        return self.fspath, 0, "bake: %s" % self.name
+
+    def repr_failure(self, excinfo):
+        if isinstance(excinfo.value, ExpectedBakeOutputError):
+            return ('\n'.join(excinfo.value.args[0]))
+        return super(BakeTestItem, self).repr_failure(excinfo)
+
+
+class ExpectedBakeOutputError(Exception):
+    pass
+
+
+def _add_mock_files(fs, parent_path, spec):
+    for name, subspec in spec.items():
+        path = os.path.join(parent_path, name)
+        if isinstance(subspec, str):
+            fs.withFile(path, subspec)
+        elif isinstance(subspec, dict):
+            _add_mock_files(fs, path, subspec)
+
+
+def _compare_dicts(left, right, basepath=''):
+    key_diff = set(left.keys()) ^ set(right.keys())
+    if key_diff:
+        extra_left = set(left.keys()) - set(right.keys())
+        if extra_left:
+            return (["Left contains more items: "] +
+                    ['- %s/%s' % (basepath, k) for k in extra_left])
+        extra_right = set(right.keys()) - set(left.keys())
+        if extra_right:
+            return (["Right contains more items: "] +
+                    ['- %s/%s' % (basepath, k) for k in extra_right])
+        return ["Unknown difference"]
+
+    for key in left.keys():
+        lv = left[key]
+        rv = right[key]
+        childpath = basepath + '/' + key
+        if type(lv) != type(rv):
+            return (["Different items: ",
+                     "%s/%s: %s" % (basepath, key, pprint.pformat(lv)),
+                     "%s/%s: %s" % (basepath, key, pprint.pformat(rv))])
+
+        if isinstance(lv, dict):
+            r = _compare_dicts(lv, rv, childpath)
+            if r:
+                return r
+        elif isinstance(lv, list):
+            r = _compare_lists(lv, rv, childpath)
+            if r:
+                return r
+        elif lv != rv:
+            return (["Different items: ",
+                     "%s/%s: %s" % (basepath, key, pprint.pformat(lv)),
+                     "%s/%s: %s" % (basepath, key, pprint.pformat(rv))])
+    return None
+
+
+def _compare_lists(left, right):
+    for i in range(min(len(left), len(right))):
+        l = left[i]
+        r = right[i]
+        if type(l) != type(r):
+            return ['Different items at index %d:' % i,
+                    pprint.pformat(l),
+                    pprint.pformat(r)]
+        if isinstance(l, dict):
+            r = _compare_dicts(l, r)
+            if r:
+                return r
+        elif isinstance(l, list):
+            r = _compare_lists(l, r)
+            if r:
+                return r
+        elif l != r:
+            return ['Different items at index %d:' % i,
+                    pprint.pformat(l),
+                    pprint.pformat(r)]
+    return None
+