diff --git a/wlauto/tests/test_exec_control.py b/wlauto/tests/test_exec_control.py
new file mode 100644
index 00000000..490239d2
--- /dev/null
+++ b/wlauto/tests/test_exec_control.py
@@ -0,0 +1,269 @@
+# Copyright 2013-2015 ARM Limited
+#
+# 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.
+#
+
+
+# pylint: disable=W0231,W0613,E0611,W0603,R0201
+from unittest import TestCase
+
+from nose.tools import assert_equal, assert_raises
+
+from wlauto.utils.exec_control import (init_environment, reset_environment,
+ activate_environment, once,
+ once_per_class, once_per_instance)
+
+class TestClass(object):
+
+ def __init__(self):
+ self.count = 0
+
+ @once
+ def initilize_once(self):
+ self.count += 1
+
+ @once_per_class
+ def initilize_once_per_class(self):
+ self.count += 1
+
+ @once_per_instance
+ def initilize_once_per_instance(self):
+ self.count += 1
+
+
+class SubClass(TestClass):
+
+ def __init__(self):
+ super(SubClass, self).__init__()
+
+
+class SubSubClass(SubClass):
+
+ def __init__(self):
+ super(SubSubClass, self).__init__()
+
+
+class AnotherClass(object):
+
+ def __init__(self):
+ self.count = 0
+
+ @once
+ def initilize_once(self):
+ self.count += 1
+
+ @once_per_class
+ def initilize_once_per_class(self):
+ self.count += 1
+
+ @once_per_instance
+ def initilize_once_per_instance(self):
+ self.count += 1
+
+
+class EnvironmentManagementTest(TestCase):
+
+ def test_duplicate_environment(self):
+ init_environment('ENVIRONMENT')
+ assert_raises(ValueError, init_environment, 'ENVIRONMENT')
+
+ def test_reset_missing_environment(self):
+ assert_raises(ValueError, reset_environment, 'MISSING')
+
+ def test_reset_current_environment(self):
+ activate_environment('CURRENT_ENVIRONMENT')
+ t1 = TestClass()
+ t1.initilize_once()
+ assert_equal(t1.count, 1)
+
+ reset_environment()
+ t1.initilize_once()
+ assert_equal(t1.count, 2)
+
+ def test_switch_environment(self):
+ activate_environment('ENVIRONMENT1')
+ t1 = TestClass()
+ t1.initilize_once()
+ assert_equal(t1.count, 1)
+
+ activate_environment('ENVIRONMENT2')
+ t1.initilize_once()
+ assert_equal(t1.count, 2)
+
+ activate_environment('ENVIRONMENT1')
+ t1.initilize_once()
+ assert_equal(t1.count, 2)
+
+ def test_reset_environment_name(self):
+ activate_environment('ENVIRONMENT')
+ t1 = TestClass()
+ t1.initilize_once()
+ assert_equal(t1.count, 1)
+
+ reset_environment('ENVIRONMENT')
+ t1.initilize_once()
+ assert_equal(t1.count, 2)
+
+
+class OnlyOnceEnvironmentTest(TestCase):
+
+ def setUp(self):
+ activate_environment('TEST_ENVIRONMENT')
+
+ def tearDown(self):
+ reset_environment('TEST_ENVIRONMENT')
+
+ def test_single_instance(self):
+ t1 = TestClass()
+ ac = AnotherClass()
+
+ t1.initilize_once()
+ assert_equal(t1.count, 1)
+
+ t1.initilize_once()
+ assert_equal(t1.count, 1)
+
+ ac.initilize_once()
+ assert_equal(ac.count, 1)
+
+
+ def test_mulitple_instances(self):
+ t1 = TestClass()
+ t2 = TestClass()
+
+ t1.initilize_once()
+ assert_equal(t1.count, 1)
+
+ t2.initilize_once()
+ assert_equal(t2.count, 0)
+
+
+ def test_sub_classes(self):
+ t1 = TestClass()
+ sc = SubClass()
+ ss = SubSubClass()
+
+ t1.initilize_once()
+ assert_equal(t1.count, 1)
+
+ sc.initilize_once()
+ sc.initilize_once()
+ assert_equal(sc.count, 0)
+
+ ss.initilize_once()
+ ss.initilize_once()
+ assert_equal(ss.count, 0)
+
+
+class OncePerClassEnvironmentTest(TestCase):
+
+ def setUp(self):
+ activate_environment('TEST_ENVIRONMENT')
+
+ def tearDown(self):
+ reset_environment('TEST_ENVIRONMENT')
+
+ def test_single_instance(self):
+ t1 = TestClass()
+ ac = AnotherClass()
+
+ t1.initilize_once_per_class()
+ assert_equal(t1.count, 1)
+
+ t1.initilize_once_per_class()
+ assert_equal(t1.count, 1)
+
+ ac.initilize_once_per_class()
+ assert_equal(ac.count, 1)
+
+
+ def test_mulitple_instances(self):
+ t1 = TestClass()
+ t2 = TestClass()
+
+ t1.initilize_once_per_class()
+ assert_equal(t1.count, 1)
+
+ t2.initilize_once_per_class()
+ assert_equal(t2.count, 0)
+
+
+ def test_sub_classes(self):
+ t1 = TestClass()
+ sc1 = SubClass()
+ sc2 = SubClass()
+ ss1 = SubSubClass()
+ ss2 = SubSubClass()
+
+ t1.initilize_once_per_class()
+ assert_equal(t1.count, 1)
+
+ sc1.initilize_once_per_class()
+ sc2.initilize_once_per_class()
+ assert_equal(sc1.count, 1)
+ assert_equal(sc2.count, 0)
+
+ ss1.initilize_once_per_class()
+ ss2.initilize_once_per_class()
+ assert_equal(ss1.count, 1)
+ assert_equal(ss2.count, 0)
+
+
+class OncePerInstanceEnvironmentTest(TestCase):
+
+ def setUp(self):
+ activate_environment('TEST_ENVIRONMENT')
+
+ def tearDown(self):
+ reset_environment('TEST_ENVIRONMENT')
+
+ def test_single_instance(self):
+ t1 = TestClass()
+ ac = AnotherClass()
+
+ t1.initilize_once_per_instance()
+ assert_equal(t1.count, 1)
+
+ t1.initilize_once_per_instance()
+ assert_equal(t1.count, 1)
+
+ ac.initilize_once_per_instance()
+ assert_equal(ac.count, 1)
+
+
+ def test_mulitple_instances(self):
+ t1 = TestClass()
+ t2 = TestClass()
+
+ t1.initilize_once_per_instance()
+ assert_equal(t1.count, 1)
+
+ t2.initilize_once_per_instance()
+ assert_equal(t2.count, 1)
+
+
+ def test_sub_classes(self):
+ t1 = TestClass()
+ sc = SubClass()
+ ss = SubSubClass()
+
+ t1.initilize_once_per_instance()
+ assert_equal(t1.count, 1)
+
+ sc.initilize_once_per_instance()
+ sc.initilize_once_per_instance()
+ assert_equal(sc.count, 1)
+
+ ss.initilize_once_per_instance()
+ ss.initilize_once_per_instance()
+ assert_equal(ss.count, 1)
diff --git a/wlauto/utils/exec_control.py b/wlauto/utils/exec_control.py
new file mode 100644
index 00000000..01025ee0
--- /dev/null
+++ b/wlauto/utils/exec_control.py
@@ -0,0 +1,117 @@
+from inspect import getmro
+
+# "environment" management:
+__environments = {}
+__active_environment = None
+
+
+def activate_environment(name):
+ """
+ Sets the current tracking environment to ``name``. If an
+ environment with that name does not already exist, it will be
+ created.
+ """
+ #pylint: disable=W0603
+ global __active_environment
+
+ if name not in __environments.keys():
+ init_environment(name)
+ __active_environment = name
+
+
+def init_environment(name):
+ """
+ Create a new environment called ``name``, but do not set it as the
+ current environment.
+
+ :raises: ``ValueError`` if an environment with name ``name``
+ already exists.
+ """
+ if name in __environments.keys():
+ msg = "Environment {} already exists".format(name)
+ raise ValueError(msg)
+ __environments[name] = []
+
+
+def reset_environment(name=None):
+ """
+ Reset method call tracking for environment ``name``. If ``name`` is
+ not specified or is ``None``, reset the current active environment.
+
+ :raises: ``ValueError`` if an environment with name ``name``
+ does not exist.
+ """
+
+ if name is not None:
+ if name not in __environments.keys():
+ msg = "Environment {} does not exist".format(name)
+ raise ValueError(msg)
+ __environments[name] = []
+ else:
+ if __active_environment is None:
+ raise ValueError("No Environment Active")
+ __environments[__active_environment] = []
+
+# The decorators:
+
+
+def once_per_instance(method):
+ """
+ The specified method will be invoked only once for every bound
+ instance within the environment.
+ """
+ def wrapper(*args, **kwargs):
+ if __active_environment is None:
+ raise ValueError("No Environment Active")
+ func_id = repr(args[0])
+ if func_id in __environments[__active_environment]:
+ return
+ else:
+ __environments[__active_environment].append(func_id)
+ return method(*args, **kwargs)
+
+ return wrapper
+
+
+def once_per_class(method):
+ """
+ The specified method will be invoked only once for all instances
+ of a class within the environment.
+ """
+ def wrapper(*args, **kwargs):
+ if __active_environment is None:
+ raise ValueError("No Environment Active")
+
+ func_id = repr(method.func_name) + repr(args[0].__class__)
+
+ if func_id in __environments[__active_environment]:
+ return
+ else:
+ __environments[__active_environment].append(func_id)
+ return method(*args, **kwargs)
+
+ return wrapper
+
+
+def once(method):
+
+ """
+ The specified method will be invoked only once within the
+ environment.
+ """
+ def wrapper(*args, **kwargs):
+ if __active_environment is None:
+ raise ValueError("No Environment Active")
+
+ func_id = repr(method.func_name)
+ # Store the least derived class, which isn't object, to account
+ # for subclasses.
+ func_id += repr(getmro(args[0].__class__)[-2])
+
+ if func_id in __environments[__active_environment]:
+ return
+ else:
+ __environments[__active_environment].append(func_id)
+ return method(*args, **kwargs)
+
+ return wrapper