Enable strict coverage for step module

recipe_engine/loader.py

Index: recipe_engine/loader.py
diff --git a/recipe_engine/loader.py b/recipe_engine/loader.py
index 42b6340cc4f3546c0477d59cfb632435745b807d..2ea34f3c76040b405bc8b038157886c63d49ae21 100644
--- a/recipe_engine/loader.py
+++ b/recipe_engine/loader.py
@@ -235,12 +235,17 @@ class UniverseView(collections.namedtuple('UniverseView', 'universe package')):
 
   def find_recipe(self, recipe):
     if ':' in recipe:
-      module_name, example = recipe.split(':')
-      #TODO(martinis) change to example == 'example' ? Technically a bug...
-      assert example.endswith('example')
-      subpath = os.path.join(self.package.module_dir, module_name)
-      if _is_recipe_module_dir(subpath):
-        recipe_path = os.path.join(subpath, 'example.py')
+      module_name, recipe_name = recipe.split(':')
+      module_dir = os.path.join(self.package.module_dir, module_name)
+      if _is_recipe_module_dir(module_dir):
+        if recipe_name.endswith('example'):
+          # TODO(martinis) change to example == 'example' ? Technically a bug...
+          recipe_path = os.path.join(module_dir, 'example.py')
+        elif recipe_name.startswith('tests/'):
+          recipe_path = os.path.join(
+              module_dir, 'tests', recipe_name[len('tests/'):] + '.py')
+        else:
+          raise NoSuchRecipe(recipe)
     else:
       recipe_path = os.path.join(self.package.recipe_dir, recipe)+".py"
 
@@ -312,11 +317,18 @@ class UniverseView(collections.namedtuple('UniverseView', 'universe package')):
         path, lambda f: f.endswith('.py') and f[0] != '_'):
       yield recipe, recipe[len(path)+1:-len('.py')]
 
-    path = self.package.module_dir
-    for recipe in scan_directory(
-        path, lambda f: f.endswith('example.py')):
-      module_name = os.path.dirname(recipe)[len(path)+1:]
-      yield recipe, '%s:example' % module_name
+    for module_name in self.loop_over_recipe_modules():
+      module_dir = os.path.join(self.package.module_dir, module_name)
+
+      example_path = os.path.join(module_dir, 'example.py')
+      if os.path.exists(example_path):
+        yield example_path, '%s:example' % module_name
+
+      test_dir = os.path.join(module_dir, 'tests')
+      if os.path.exists(test_dir):
+        for recipe in scan_directory(test_dir, lambda f: f.endswith('.py')):
+          yield recipe, '%s:tests/%s' % (
+              module_name, recipe[len(test_dir)+1:-len('.py')])
 
   def loop_over_recipe_modules(self):
     """Yields the paths to all the modules that this view can see."""