Adding datastore _DEFAULTS stubs in all tests that use it.

[dhermes]

NOTE: Has #664 as diffbase

Introduces

• concept of implicit for _DefaultsContainer.
• testing module for datastore for patching

Verified all test cases that would accidentally rely on _DEFAULTS implicit
behavior by using a custom _DefaultsContainer that raises when the
instance is implicit.

Main delta for the custom properties:

diff --git a/gcloud/datastore/_implicit_environ.py b/gcloud/datastore/_implicit_environ.py
index 3afc954..1d38562 100644
--- a/gcloud/datastore/_implicit_environ.py
+++ b/gcloud/datastore/_implicit_environ.py
@@ -38,9 +38,37 @@ class _DefaultsContainer(object):
 :param dataset_id: Persistent implied dataset ID from environment.
 """

-    def __init__(self, connection=None, dataset_id=None):
-        self.connection = connection
-        self.dataset_id = dataset_id
+    class FooError(Exception):
+        pass
+
+    @property
+    def dataset_id(self):
+        if self.implicit:
+            raise self.FooError
+        return self._dataset_id
+
+    @dataset_id.setter
+    def dataset_id(self, value):
+        if self.implicit:
+            raise self.FooError
+        self._dataset_id = value
+
+    @property
+    def connection(self):
+        if self.implicit:
+            raise self.FooError
+        return self._connection
+
+    @connection.setter
+    def connection(self, value):
+        if self.implicit:
+            raise self.FooError
+        self._connection = value
+
+    def __init__(self, connection=None, dataset_id=None, implicit=False):
+        self.implicit = implicit
+        self._connection = connection
+        self._dataset_id = dataset_id

 def app_engine_id():

[coveralls]

Coverage remained the same at 100.0% when pulling 1f990e0 on dhermes:lazy-loading-attempt-2 into 72b6359 on GoogleCloudPlatform:master.

[tseaver]

I don't grasp the "main delta" bit: are you saying that was stuff you used to find places relying on implicit values, but didn't check it in after fixing them?

[dhermes]

This PR is really just about using _monkey_defaults, _setup_defaults and _tear_down_defaults in tests.

The diff above is a hack I used to sniff out tests that relied on implicit behavior. It makes it so that anytime connection or dataset_id are get or set on a _DefaultsContainer, the following occurs:

        if self.implicit:
            raise self.FooError

So if the container being tested was implicit, the test would fail. (I made a custom error, so it didn't get caught by any assertRaises)

[dhermes]

@tseaver I just rebased on top of #664.

Remaining issues here?

[coveralls]

Coverage remained the same at 100.0% when pulling 5e281dd on dhermes:lazy-loading-attempt-2 into 998c724 on GoogleCloudPlatform:master.

[tseaver]

LGTM. (I think some of this commit gets backed out in #667 anyway).