diff --git a/.github/.OwlBot.lock.yaml b/.github/.OwlBot.lock.yaml
index c07f148f..7d98291c 100644
--- a/.github/.OwlBot.lock.yaml
+++ b/.github/.OwlBot.lock.yaml
@@ -1,3 +1,3 @@
 docker:
-  image: gcr.io/repo-automation-bots/owlbot-python:latest
-  digest: sha256:0ffe3bdd6c7159692df5f7744da74e5ef19966288a6bf76023e8e04e0c424d7d
+  image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
+  digest: sha256:58f73ba196b5414782605236dd0712a73541b44ff2ff4d3a36ec41092dd6fa5b
diff --git a/.github/.OwlBot.yaml b/.github/.OwlBot.yaml
index 3caf68d4..c8b40cc7 100644
--- a/.github/.OwlBot.yaml
+++ b/.github/.OwlBot.yaml
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 docker:
-  image: gcr.io/repo-automation-bots/owlbot-python:latest
+  image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
 
 begin-after-commit-hash: 7af2cb8b2b725641ac0d07e2f256d453682802e6
 
diff --git a/.kokoro/samples/lint/common.cfg b/.kokoro/samples/lint/common.cfg
index f5dddb4b..1a2b87b2 100644
--- a/.kokoro/samples/lint/common.cfg
+++ b/.kokoro/samples/lint/common.cfg
@@ -31,4 +31,4 @@ gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/python-docs-samples"
 gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/trampoline"
 
 # Use the trampoline script to run in docker.
-build_file: "python-api-core/.kokoro/trampoline.sh"
\ No newline at end of file
+build_file: "python-api-core/.kokoro/trampoline_v2.sh"
\ No newline at end of file
diff --git a/.kokoro/samples/python3.10/common.cfg b/.kokoro/samples/python3.10/common.cfg
new file mode 100644
index 00000000..40fb8d81
--- /dev/null
+++ b/.kokoro/samples/python3.10/common.cfg
@@ -0,0 +1,40 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Build logs will be here
+action {
+  define_artifacts {
+    regex: "**/*sponge_log.xml"
+  }
+}
+
+# Specify which tests to run
+env_vars: {
+    key: "RUN_TESTS_SESSION"
+    value: "py-3.10"
+}
+
+# Declare build specific Cloud project.
+env_vars: {
+    key: "BUILD_SPECIFIC_GCLOUD_PROJECT"
+    value: "python-docs-samples-tests-310"
+}
+
+env_vars: {
+    key: "TRAMPOLINE_BUILD_FILE"
+    value: "github/python-api-core/.kokoro/test-samples.sh"
+}
+
+# Configure the docker image for kokoro-trampoline.
+env_vars: {
+    key: "TRAMPOLINE_IMAGE"
+    value: "gcr.io/cloud-devrel-kokoro-resources/python-samples-testing-docker"
+}
+
+# Download secrets for samples
+gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/python-docs-samples"
+
+# Download trampoline resources.
+gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/trampoline"
+
+# Use the trampoline script to run in docker.
+build_file: "python-api-core/.kokoro/trampoline_v2.sh"
\ No newline at end of file
diff --git a/.kokoro/samples/python3.10/continuous.cfg b/.kokoro/samples/python3.10/continuous.cfg
new file mode 100644
index 00000000..a1c8d975
--- /dev/null
+++ b/.kokoro/samples/python3.10/continuous.cfg
@@ -0,0 +1,6 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "True"
+}
\ No newline at end of file
diff --git a/.kokoro/samples/python3.10/periodic-head.cfg b/.kokoro/samples/python3.10/periodic-head.cfg
new file mode 100644
index 00000000..a18c0cfc
--- /dev/null
+++ b/.kokoro/samples/python3.10/periodic-head.cfg
@@ -0,0 +1,11 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "True"
+}
+
+env_vars: {
+    key: "TRAMPOLINE_BUILD_FILE"
+    value: "github/python-api-core/.kokoro/test-samples-against-head.sh"
+}
diff --git a/.kokoro/samples/python3.10/periodic.cfg b/.kokoro/samples/python3.10/periodic.cfg
new file mode 100644
index 00000000..71cd1e59
--- /dev/null
+++ b/.kokoro/samples/python3.10/periodic.cfg
@@ -0,0 +1,6 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "False"
+}
diff --git a/.kokoro/samples/python3.10/presubmit.cfg b/.kokoro/samples/python3.10/presubmit.cfg
new file mode 100644
index 00000000..a1c8d975
--- /dev/null
+++ b/.kokoro/samples/python3.10/presubmit.cfg
@@ -0,0 +1,6 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+env_vars: {
+    key: "INSTALL_LIBRARY_FROM_SOURCE"
+    value: "True"
+}
\ No newline at end of file
diff --git a/.kokoro/samples/python3.6/common.cfg b/.kokoro/samples/python3.6/common.cfg
index 7b4f5cd0..3bb6b3a6 100644
--- a/.kokoro/samples/python3.6/common.cfg
+++ b/.kokoro/samples/python3.6/common.cfg
@@ -37,4 +37,4 @@ gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/python-docs-samples"
 gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/trampoline"
 
 # Use the trampoline script to run in docker.
-build_file: "python-api-core/.kokoro/trampoline.sh"
\ No newline at end of file
+build_file: "python-api-core/.kokoro/trampoline_v2.sh"
\ No newline at end of file
diff --git a/.kokoro/samples/python3.6/periodic.cfg b/.kokoro/samples/python3.6/periodic.cfg
index 50fec964..71cd1e59 100644
--- a/.kokoro/samples/python3.6/periodic.cfg
+++ b/.kokoro/samples/python3.6/periodic.cfg
@@ -3,4 +3,4 @@
 env_vars: {
     key: "INSTALL_LIBRARY_FROM_SOURCE"
     value: "False"
-}
\ No newline at end of file
+}
diff --git a/.kokoro/samples/python3.7/common.cfg b/.kokoro/samples/python3.7/common.cfg
index 1198d7ba..a3aa10b5 100644
--- a/.kokoro/samples/python3.7/common.cfg
+++ b/.kokoro/samples/python3.7/common.cfg
@@ -37,4 +37,4 @@ gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/python-docs-samples"
 gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/trampoline"
 
 # Use the trampoline script to run in docker.
-build_file: "python-api-core/.kokoro/trampoline.sh"
\ No newline at end of file
+build_file: "python-api-core/.kokoro/trampoline_v2.sh"
\ No newline at end of file
diff --git a/.kokoro/samples/python3.7/periodic.cfg b/.kokoro/samples/python3.7/periodic.cfg
index 50fec964..71cd1e59 100644
--- a/.kokoro/samples/python3.7/periodic.cfg
+++ b/.kokoro/samples/python3.7/periodic.cfg
@@ -3,4 +3,4 @@
 env_vars: {
     key: "INSTALL_LIBRARY_FROM_SOURCE"
     value: "False"
-}
\ No newline at end of file
+}
diff --git a/.kokoro/samples/python3.8/common.cfg b/.kokoro/samples/python3.8/common.cfg
index b7ec7f5e..20c941aa 100644
--- a/.kokoro/samples/python3.8/common.cfg
+++ b/.kokoro/samples/python3.8/common.cfg
@@ -37,4 +37,4 @@ gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/python-docs-samples"
 gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/trampoline"
 
 # Use the trampoline script to run in docker.
-build_file: "python-api-core/.kokoro/trampoline.sh"
\ No newline at end of file
+build_file: "python-api-core/.kokoro/trampoline_v2.sh"
\ No newline at end of file
diff --git a/.kokoro/samples/python3.8/periodic.cfg b/.kokoro/samples/python3.8/periodic.cfg
index 50fec964..71cd1e59 100644
--- a/.kokoro/samples/python3.8/periodic.cfg
+++ b/.kokoro/samples/python3.8/periodic.cfg
@@ -3,4 +3,4 @@
 env_vars: {
     key: "INSTALL_LIBRARY_FROM_SOURCE"
     value: "False"
-}
\ No newline at end of file
+}
diff --git a/.kokoro/samples/python3.9/common.cfg b/.kokoro/samples/python3.9/common.cfg
index cf034ec1..234887c6 100644
--- a/.kokoro/samples/python3.9/common.cfg
+++ b/.kokoro/samples/python3.9/common.cfg
@@ -37,4 +37,4 @@ gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/python-docs-samples"
 gfile_resources: "/bigstore/cloud-devrel-kokoro-resources/trampoline"
 
 # Use the trampoline script to run in docker.
-build_file: "python-api-core/.kokoro/trampoline.sh"
\ No newline at end of file
+build_file: "python-api-core/.kokoro/trampoline_v2.sh"
\ No newline at end of file
diff --git a/.kokoro/samples/python3.9/periodic.cfg b/.kokoro/samples/python3.9/periodic.cfg
index 50fec964..71cd1e59 100644
--- a/.kokoro/samples/python3.9/periodic.cfg
+++ b/.kokoro/samples/python3.9/periodic.cfg
@@ -3,4 +3,4 @@
 env_vars: {
     key: "INSTALL_LIBRARY_FROM_SOURCE"
     value: "False"
-}
\ No newline at end of file
+}
diff --git a/.kokoro/test-samples-against-head.sh b/.kokoro/test-samples-against-head.sh
index a7858e4c..ba3a707b 100755
--- a/.kokoro/test-samples-against-head.sh
+++ b/.kokoro/test-samples-against-head.sh
@@ -23,6 +23,4 @@ set -eo pipefail
 # Enables `**` to include files nested inside sub-folders
 shopt -s globstar
 
-cd github/python-api-core
-
 exec .kokoro/test-samples-impl.sh
diff --git a/.kokoro/test-samples.sh b/.kokoro/test-samples.sh
index ee3146bd..11c042d3 100755
--- a/.kokoro/test-samples.sh
+++ b/.kokoro/test-samples.sh
@@ -24,8 +24,6 @@ set -eo pipefail
 # Enables `**` to include files nested inside sub-folders
 shopt -s globstar
 
-cd github/python-api-core
-
 # Run periodic samples tests at latest release
 if [[ $KOKORO_BUILD_ARTIFACTS_SUBDIR = *"periodic"* ]]; then
     # preserving the test runner implementation.
diff --git a/.repo-metadata.json b/.repo-metadata.json
index 59aa936d..e16c9d27 100644
--- a/.repo-metadata.json
+++ b/.repo-metadata.json
@@ -1,10 +1,12 @@
 {
-  "name": "google-api-core",
-  "name_pretty": "Google API client core library",
-  "client_documentation": "https://googleapis.dev/python/google-api-core/latest",
-  "release_level": "ga",
-  "language": "python",
-  "library_type": "CORE",
-  "repo": "googleapis/python-api-core",
-  "distribution_name": "google-api-core"
-}
\ No newline at end of file
+    "name": "google-api-core",
+    "name_pretty": "Google API client core library",
+    "client_documentation": "https://googleapis.dev/python/google-api-core/latest",
+    "release_level": "ga",
+    "language": "python",
+    "library_type": "CORE",
+    "repo": "googleapis/python-api-core",
+    "distribution_name": "google-api-core",
+    "default_version": "",
+    "codeowner_team": "@googleapis/actools-python"
+}
diff --git a/.trampolinerc b/.trampolinerc
index 383b6ec8..0eee72ab 100644
--- a/.trampolinerc
+++ b/.trampolinerc
@@ -16,15 +16,26 @@
 
 # Add required env vars here.
 required_envvars+=(
-    "STAGING_BUCKET"
-    "V2_STAGING_BUCKET"
 )
 
 # Add env vars which are passed down into the container here.
 pass_down_envvars+=(
+    "NOX_SESSION"
+    ###############
+    # Docs builds
+    ###############
     "STAGING_BUCKET"
     "V2_STAGING_BUCKET"
-    "NOX_SESSION"
+    ##################
+    # Samples builds
+    ##################
+    "INSTALL_LIBRARY_FROM_SOURCE"
+    "RUN_TESTS_SESSION"
+    "BUILD_SPECIFIC_GCLOUD_PROJECT"
+    # Target directories.
+    "RUN_TESTS_DIRS"
+    # The nox session to run.
+    "RUN_TESTS_SESSION"
 )
 
 # Prevent unintentional override on the default image.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index fdca59ba..00910e1f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,15 @@
 
 [1]: https://pypi.org/project/google-api-core/#history
 
+## [2.1.0](https://www.github.com/googleapis/python-api-core/compare/v2.0.1...v2.1.0) (2021-10-05)
+
+
+### Features
+
+* add grpc transcoding + tests ([#259](https://www.github.com/googleapis/python-api-core/issues/259)) ([afe0fa1](https://www.github.com/googleapis/python-api-core/commit/afe0fa14c21289c8244606a9f81544cff8ac5f7c))
+* Add helper function to format query_params for rest transport. ([#275](https://www.github.com/googleapis/python-api-core/issues/275)) ([1c5eb4d](https://www.github.com/googleapis/python-api-core/commit/1c5eb4df93d78e791082d9282330ebf0faacd222))
+* add support for Python 3.10 ([#284](https://www.github.com/googleapis/python-api-core/issues/284)) ([a422a5d](https://www.github.com/googleapis/python-api-core/commit/a422a5d72cb6f363d57e7a4effe421ba8e049cde))
+
 ### [2.0.1](https://www.github.com/googleapis/python-api-core/compare/v2.0.0...v2.0.1) (2021-08-31)
 
 
diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index 6db668ef..6b375f03 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -21,7 +21,7 @@ In order to add a feature:
   documentation.
 
 - The feature must work fully on the following CPython versions:
-  3.6, 3.7, 3.8 and 3.9 on both UNIX and Windows.
+  3.6, 3.7, 3.8, 3.9, and 3.10 on both UNIX and Windows.
 
 - The feature must not add unnecessary dependencies (where
   "unnecessary" is of course subjective, but new dependencies should
@@ -71,7 +71,7 @@ We use `nox <https://nox.readthedocs.io/en/latest/>`__ to instrument our tests.
 
 - To run a single unit test::
 
-    $ nox -s unit-3.9 -- -k <name of test>
+    $ nox -s unit-3.10 -- -k <name of test>
 
 
   .. note::
@@ -201,11 +201,13 @@ We support:
 -  `Python 3.7`_
 -  `Python 3.8`_
 -  `Python 3.9`_
+-  `Python 3.10`_
 
 .. _Python 3.6: https://docs.python.org/3.6/
 .. _Python 3.7: https://docs.python.org/3.7/
 .. _Python 3.8: https://docs.python.org/3.8/
 .. _Python 3.9: https://docs.python.org/3.9/
+.. _Python 3.10: https://docs.python.org/3.10/
 
 
 Supported versions can be found in our ``noxfile.py`` `config`_.
diff --git a/google/api_core/bidi.py b/google/api_core/bidi.py
index 56a021a9..4b4963f7 100644
--- a/google/api_core/bidi.py
+++ b/google/api_core/bidi.py
@@ -727,7 +727,7 @@ def resume(self):
         """Resumes the response stream."""
         with self._wake:
             self._paused = False
-            self._wake.notifyAll()
+            self._wake.notify_all()
 
     @property
     def is_paused(self):
diff --git a/google/api_core/rest_helpers.py b/google/api_core/rest_helpers.py
new file mode 100644
index 00000000..23fb614f
--- /dev/null
+++ b/google/api_core/rest_helpers.py
@@ -0,0 +1,94 @@
+# Copyright 2021 Google LLC
+#
+# 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.
+
+"""Helpers for rest transports."""
+
+import functools
+import operator
+
+
+def flatten_query_params(obj):
+    """Flatten a nested dict into a list of (name,value) tuples.
+
+    The result is suitable for setting query params on an http request.
+
+    .. code-block:: python
+
+        >>> obj = {'a':
+        ...         {'b':
+        ...           {'c': ['x', 'y', 'z']} },
+        ...      'd': 'uvw', }
+        >>> flatten_query_params(obj)
+        [('a.b.c', 'x'), ('a.b.c', 'y'), ('a.b.c', 'z'), ('d', 'uvw')]
+
+    Note that, as described in
+    https://github.com/googleapis/googleapis/blob/48d9fb8c8e287c472af500221c6450ecd45d7d39/google/api/http.proto#L117,
+    repeated fields (i.e. list-valued fields) may only contain primitive types (not lists or dicts).
+    This is enforced in this function.
+
+    Args:
+      obj: a nested dictionary (from json), or None
+
+    Returns: a list of tuples, with each tuple having a (possibly) multi-part name
+      and a scalar value.
+
+    Raises:
+      TypeError if obj is not a dict or None
+      ValueError if obj contains a list of non-primitive values.
+    """
+
+    if obj is not None and not isinstance(obj, dict):
+        raise TypeError("flatten_query_params must be called with dict object")
+
+    return _flatten(obj, key_path=[])
+
+
+def _flatten(obj, key_path):
+    if obj is None:
+        return []
+    if isinstance(obj, dict):
+        return _flatten_dict(obj, key_path=key_path)
+    if isinstance(obj, list):
+        return _flatten_list(obj, key_path=key_path)
+    return _flatten_value(obj, key_path=key_path)
+
+
+def _is_primitive_value(obj):
+    if obj is None:
+        return False
+
+    if isinstance(obj, (list, dict)):
+        raise ValueError("query params may not contain repeated dicts or lists")
+
+    return True
+
+
+def _flatten_value(obj, key_path):
+    return [(".".join(key_path), obj)]
+
+
+def _flatten_dict(obj, key_path):
+    items = (_flatten(value, key_path=key_path + [key]) for key, value in obj.items())
+    return functools.reduce(operator.concat, items, [])
+
+
+def _flatten_list(elems, key_path):
+    # Only lists of scalar values are supported.
+    # The name (key_path) is repeated for each value.
+    items = (
+        _flatten_value(elem, key_path=key_path)
+        for elem in elems
+        if _is_primitive_value(elem)
+    )
+    return functools.reduce(operator.concat, items, [])
diff --git a/google/api_core/version.py b/google/api_core/version.py
index 956a957b..8b5d3328 100644
--- a/google/api_core/version.py
+++ b/google/api_core/version.py
@@ -12,4 +12,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-__version__ = "2.0.1"
+__version__ = "2.1.0"
diff --git a/noxfile.py b/noxfile.py
index 6478bfde..617dc580 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -121,7 +121,7 @@ def default(session):
         session.run(*pytest_args)
 
 
-@nox.session(python=["3.6", "3.7", "3.8", "3.9"])
+@nox.session(python=["3.6", "3.7", "3.8", "3.9", "3.10"])
 def unit(session):
     """Run the unit test suite."""
     default(session)
diff --git a/setup.py b/setup.py
index e99c7da2..8e59cf41 100644
--- a/setup.py
+++ b/setup.py
@@ -87,6 +87,7 @@
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",
+        "Programming Language :: Python :: 3.10",
         "Operating System :: OS Independent",
         "Topic :: Internet",
     ],
diff --git a/tests/unit/test_grpc_helpers.py b/tests/unit/test_grpc_helpers.py
index ae4f08fa..8c0524e9 100644
--- a/tests/unit/test_grpc_helpers.py
+++ b/tests/unit/test_grpc_helpers.py
@@ -69,6 +69,128 @@ def test_wrap_unary_errors():
     assert exc_info.value.response == grpc_error
 
 
+class Test_StreamingResponseIterator:
+    @staticmethod
+    def _make_wrapped(*items):
+        return iter(items)
+
+    @staticmethod
+    def _make_one(wrapped, **kw):
+        return grpc_helpers._StreamingResponseIterator(wrapped, **kw)
+
+    def test_ctor_defaults(self):
+        wrapped = self._make_wrapped("a", "b", "c")
+        iterator = self._make_one(wrapped)
+        assert iterator._stored_first_result == "a"
+        assert list(wrapped) == ["b", "c"]
+
+    def test_ctor_explicit(self):
+        wrapped = self._make_wrapped("a", "b", "c")
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+        assert getattr(iterator, "_stored_first_result", self) is self
+        assert list(wrapped) == ["a", "b", "c"]
+
+    def test_ctor_w_rpc_error_on_prefetch(self):
+        wrapped = mock.MagicMock()
+        wrapped.__next__.side_effect = grpc.RpcError()
+
+        with pytest.raises(grpc.RpcError):
+            self._make_one(wrapped)
+
+    def test___iter__(self):
+        wrapped = self._make_wrapped("a", "b", "c")
+        iterator = self._make_one(wrapped)
+        assert iter(iterator) is iterator
+
+    def test___next___w_cached_first_result(self):
+        wrapped = self._make_wrapped("a", "b", "c")
+        iterator = self._make_one(wrapped)
+        assert next(iterator) == "a"
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+        assert next(iterator) == "b"
+        assert next(iterator) == "c"
+
+    def test___next___wo_cached_first_result(self):
+        wrapped = self._make_wrapped("a", "b", "c")
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+        assert next(iterator) == "a"
+        assert next(iterator) == "b"
+        assert next(iterator) == "c"
+
+    def test___next___w_rpc_error(self):
+        wrapped = mock.MagicMock()
+        wrapped.__next__.side_effect = grpc.RpcError()
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+
+        with pytest.raises(exceptions.GoogleAPICallError):
+            next(iterator)
+
+    def test_add_callback(self):
+        wrapped = mock.MagicMock()
+        callback = mock.Mock(spec={})
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+
+        assert iterator.add_callback(callback) is wrapped.add_callback.return_value
+
+        wrapped.add_callback.assert_called_once_with(callback)
+
+    def test_cancel(self):
+        wrapped = mock.MagicMock()
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+
+        assert iterator.cancel() is wrapped.cancel.return_value
+
+        wrapped.cancel.assert_called_once_with()
+
+    def test_code(self):
+        wrapped = mock.MagicMock()
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+
+        assert iterator.code() is wrapped.code.return_value
+
+        wrapped.code.assert_called_once_with()
+
+    def test_details(self):
+        wrapped = mock.MagicMock()
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+
+        assert iterator.details() is wrapped.details.return_value
+
+        wrapped.details.assert_called_once_with()
+
+    def test_initial_metadata(self):
+        wrapped = mock.MagicMock()
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+
+        assert iterator.initial_metadata() is wrapped.initial_metadata.return_value
+
+        wrapped.initial_metadata.assert_called_once_with()
+
+    def test_is_active(self):
+        wrapped = mock.MagicMock()
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+
+        assert iterator.is_active() is wrapped.is_active.return_value
+
+        wrapped.is_active.assert_called_once_with()
+
+    def test_time_remaining(self):
+        wrapped = mock.MagicMock()
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+
+        assert iterator.time_remaining() is wrapped.time_remaining.return_value
+
+        wrapped.time_remaining.assert_called_once_with()
+
+    def test_trailing_metadata(self):
+        wrapped = mock.MagicMock()
+        iterator = self._make_one(wrapped, prefetch_first_result=False)
+
+        assert iterator.trailing_metadata() is wrapped.trailing_metadata.return_value
+
+        wrapped.trailing_metadata.assert_called_once_with()
+
+
 def test_wrap_stream_okay():
     expected_responses = [1, 2, 3]
     callable_ = mock.Mock(spec=["__call__"], return_value=iter(expected_responses))
diff --git a/tests/unit/test_rest_helpers.py b/tests/unit/test_rest_helpers.py
new file mode 100644
index 00000000..5932fa55
--- /dev/null
+++ b/tests/unit/test_rest_helpers.py
@@ -0,0 +1,77 @@
+# Copyright 2021 Google LLC
+#
+# 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.
+
+import pytest
+
+from google.api_core import rest_helpers
+
+
+def test_flatten_simple_value():
+    with pytest.raises(TypeError):
+        rest_helpers.flatten_query_params("abc")
+
+
+def test_flatten_list():
+    with pytest.raises(TypeError):
+        rest_helpers.flatten_query_params(["abc", "def"])
+
+
+def test_flatten_none():
+    assert rest_helpers.flatten_query_params(None) == []
+
+
+def test_flatten_empty_dict():
+    assert rest_helpers.flatten_query_params({}) == []
+
+
+def test_flatten_simple_dict():
+    assert rest_helpers.flatten_query_params({"a": "abc", "b": "def"}) == [
+        ("a", "abc"),
+        ("b", "def"),
+    ]
+
+
+def test_flatten_repeated_field():
+    assert rest_helpers.flatten_query_params({"a": ["x", "y", "z", None]}) == [
+        ("a", "x"),
+        ("a", "y"),
+        ("a", "z"),
+    ]
+
+
+def test_flatten_nested_dict():
+    obj = {"a": {"b": {"c": ["x", "y", "z"]}}, "d": {"e": "uvw"}}
+    expected_result = [("a.b.c", "x"), ("a.b.c", "y"), ("a.b.c", "z"), ("d.e", "uvw")]
+
+    assert rest_helpers.flatten_query_params(obj) == expected_result
+
+
+def test_flatten_repeated_dict():
+    obj = {
+        "a": {"b": {"c": [{"v": 1}, {"v": 2}]}},
+        "d": "uvw",
+    }
+
+    with pytest.raises(ValueError):
+        rest_helpers.flatten_query_params(obj)
+
+
+def test_flatten_repeated_list():
+    obj = {
+        "a": {"b": {"c": [["e", "f"], ["g", "h"]]}},
+        "d": "uvw",
+    }
+
+    with pytest.raises(ValueError):
+        rest_helpers.flatten_query_params(obj)