feat(firestore): add support of emulator to run system tests on emulator (#31)

* feat(firestore): add support of emulator to run system tests on emulator

* feat(firestore): add test_utils folder for support

* docs(firestore): remove test_utils folder as added in nox file

Co-authored-by: Christopher Wilcox <crwilcox@google.com>

Author: HemangChothani

tests/system/test_system.py

@@ -30,7 +30,9 @@
 from google.cloud._helpers import _pb_timestamp_to_datetime
 from google.cloud._helpers import UTC
 from google.cloud import firestore_v1 as firestore
+from google.cloud.firestore_v1.client import _FIRESTORE_EMULATOR_HOST
 from test_utils.system import unique_resource_id
+from test_utils.system import EmulatorCreds
 
 from time import sleep
 
@@ -41,11 +43,19 @@
 DOCUMENT_EXISTS = "Document already exists: "
 UNIQUE_RESOURCE_ID = unique_resource_id("-")
 
+FIRESTORE_EMULATOR = os.getenv(_FIRESTORE_EMULATOR_HOST) is not None
+
 
 @pytest.fixture(scope=u"module")
 def client():
-    credentials = service_account.Credentials.from_service_account_file(FIRESTORE_CREDS)
-    project = FIRESTORE_PROJECT or credentials.project_id
+    if FIRESTORE_EMULATOR:
+        credentials = EmulatorCreds()
+        project = FIRESTORE_PROJECT
+    else:
+        credentials = service_account.Credentials.from_service_account_file(
+            FIRESTORE_CREDS
+        )
+        project = FIRESTORE_PROJECT or credentials.project_id
     yield firestore.Client(project=project, credentials=credentials)
 
 
@@ -126,6 +136,7 @@ def test_create_document_w_subcollection(client, cleanup):
     assert sorted(child.id for child in children) == sorted(child_ids)
 
 
+@pytest.mark.skipif(FIRESTORE_EMULATOR, reason="Internal Issue b/137866686")
 def test_cannot_use_foreign_key(client, cleanup):
     document_id = "cannot" + UNIQUE_RESOURCE_ID
     document = client.document("foreign-key", document_id)
@@ -280,6 +291,7 @@ def test_document_update_w_int_field(client, cleanup):
     assert snapshot1.to_dict() == expected
 
 
+@pytest.mark.skipif(FIRESTORE_EMULATOR, reason="Internal Issue b/137867104")
 def test_update_document(client, cleanup):
     document_id = "for-update" + UNIQUE_RESOURCE_ID
     document = client.document("made", document_id)
@@ -861,6 +873,7 @@ def test_collection_group_queries_filters(client, cleanup):
     assert found == set(["cg-doc2"])
 
 
+@pytest.mark.skipif(FIRESTORE_EMULATOR, reason="Internal Issue b/137865992")
 def test_get_all(client, cleanup):
     collection_name = "get-all" + UNIQUE_RESOURCE_ID