diff --git a/poetry.lock b/poetry.lock
index cf634c6..1f8d70d 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -209,6 +209,24 @@ files = [
 [package.dependencies]
 colorama = {version = "*", markers = "platform_system == \"Windows\""}
 
+[[package]]
+name = "cloud-storage-mocker"
+version = "0.3.4"
+description = "Mocker library of Google Cloud Storage with local filesystem mounting."
+optional = false
+python-versions = "<3.13,>=3.8"
+files = [
+    {file = "cloud_storage_mocker-0.3.4-py3-none-any.whl", hash = "sha256:87be5ad2fa6f34f27e4aec9654ccd4f82e26f988a4267d076ff72f21ec1e1715"},
+    {file = "cloud_storage_mocker-0.3.4.tar.gz", hash = "sha256:a16bac982fbf2810340295c6d556e5e95b79a90671151d8657b868c0583ac64f"},
+]
+
+[package.dependencies]
+google-cloud-storage = ">=2.7.0"
+
+[package.extras]
+dev = ["black (>=22.10)", "flake8 (>=5.0)", "isort (>=5.10)", "mypy (>=0.991)", "pyproject-flake8 (>=5.0)", "pytest (>=7.1)"]
+mypy = ["mypy (>=0.991)", "pytest (>=7.1)"]
+
 [[package]]
 name = "colorama"
 version = "0.4.6"
@@ -1611,5 +1629,5 @@ testing = ["big-O", "jaraco.functools", "jaraco.itertools", "more-itertools", "p
 
 [metadata]
 lock-version = "2.0"
-python-versions = "^3.10"
-content-hash = "3f1eec08ebc6ac6b59b3b81761274cba71bf359f22981440d3af0ca67b7cbcfe"
+python-versions = ">=3.10,<3.13"
+content-hash = "ef11eb8fb80249022bab13891c8e931e5695c6f4e1a5afda987d1f7f338d6cdd"
diff --git a/pyproject.toml b/pyproject.toml
index 55e4947..356952c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,7 +7,7 @@ license = "MPL-2.0"
 readme = "README.md"
 
 [tool.poetry.dependencies]
-python = "^3.10"
+python = ">=3.10,<3.13"
 google-api-core = "^2.19.0"
 google-cloud-storage = "^2.16.0"
 wandb = "^0.16.6"
@@ -18,6 +18,7 @@ ruff = "^0.4.3"
 
 [tool.poetry.group.dev.dependencies]
 pytest = "^8.2.0"
+cloud-storage-mocker = "^0.3.4"
 
 [tool.pytest.ini_options]
 markers = [
diff --git a/src/mozmlops/cloud_storage_api_client.py b/src/mozmlops/cloud_storage_api_client.py
index 6d7394b..9729fac 100644
--- a/src/mozmlops/cloud_storage_api_client.py
+++ b/src/mozmlops/cloud_storage_api_client.py
@@ -40,7 +40,7 @@ def store(self, data: bytes, storage_path: str) -> str:
         client = storage.Client(project=self.gcs_project_name)
 
         # Raises an exception if the bucket name cannot be found
-        bucket = client.get_bucket(self.gcs_bucket_name)
+        bucket = client.bucket(self.gcs_bucket_name)
 
         blob = bucket.blob(storage_path)
 
@@ -74,7 +74,7 @@ def fetch(self, remote_path: str, local_path: str) -> str:
         from google.cloud import storage
 
         client = storage.Client(project=self.gcs_project_name)
-        bucket = client.get_bucket(self.gcs_bucket_name)
+        bucket = client.bucket(self.gcs_bucket_name)
 
         blob = bucket.blob(remote_path)
 
@@ -83,6 +83,7 @@ def fetch(self, remote_path: str, local_path: str) -> str:
         p.parent.mkdir(parents=True, exist_ok=True)
 
         blob.download_to_filename(local_path)
+        return local_path
 
     def __delete(self, remote_path: str) -> str:
         """
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..5c9188c
--- /dev/null
+++ b/tests/__init__.py
@@ -0,0 +1,6 @@
+import sys
+import os
+
+# To avoid ModuleNotFound errors in tests while attempting to import test subjects.
+# To be investigated here: https://mozilla-hub.atlassian.net/browse/DENG-3667
+sys.path.append(f"{os.getcwd()}/src")
diff --git a/tests/integration/__init__.py b/tests/integration/__init__.py
index 5c9188c..e69de29 100644
--- a/tests/integration/__init__.py
+++ b/tests/integration/__init__.py
@@ -1,6 +0,0 @@
-import sys
-import os
-
-# To avoid ModuleNotFound errors in tests while attempting to import test subjects.
-# To be investigated here: https://mozilla-hub.atlassian.net/browse/DENG-3667
-sys.path.append(f"{os.getcwd()}/src")
diff --git a/tests/unit/test_cloud_storage_api_client.py b/tests/unit/test_cloud_storage_api_client.py
new file mode 100644
index 0000000..dc94042
--- /dev/null
+++ b/tests/unit/test_cloud_storage_api_client.py
@@ -0,0 +1,90 @@
+import io
+import pathlib
+from datetime import datetime
+
+import google.cloud.storage  # type: ignore[import]
+from cloud_storage_mocker import Mount
+from cloud_storage_mocker import patch as gcs_patch
+from mozmlops.cloud_storage_api_client import CloudStorageAPIClient
+
+
+def test_store__stores_file_on_gcs(tmp_path: pathlib.Path) -> None:
+    """
+    This is a unit test that checks whether we called the GCS API
+    according to the expectations of this GCS mocking library:
+
+    https://github.com/odashi/cloud-storage-mocker
+
+    The library does not support mocks for all GCS operations,
+    and it is not maintained by the team that builds the GCS API.
+
+    If this test fails and it's unclear why,
+    run the integration tests to check our integration behavior for real
+    to see if something is wrong:
+
+    pytest -m integration
+    """
+
+    # Given the following mocked bucket
+    with gcs_patch(
+        [
+            Mount("testbucket", tmp_path / "src", readable=True, writable=True),
+        ],
+    ):
+        # When our API Client stores data in a file on GCS:
+        storage_client = CloudStorageAPIClient(project_name="testproject", bucket_name="testbucket")
+
+        string_to_store = "Ada Lovelace"
+        timestamp = datetime.now().strftime("%Y-%m-%d-%H-%M-%S")
+        filename_to_store_it_at = f"first_computer_programmer_{timestamp}.txt"
+        encoded_string = string_to_store.encode(encoding='utf-8')
+
+        filepath = storage_client.store(data=encoded_string, storage_path=filename_to_store_it_at)
+        assert filepath == filename_to_store_it_at
+
+        # Then we can do the steps to download the file from mock GCS:
+        mock_client = google.cloud.storage.Client()
+        blob = mock_client.bucket("testbucket").blob(filename_to_store_it_at)
+        assert blob.download_as_text() == string_to_store
+
+def test_fetch__gets_file_off_gcs(tmp_path: pathlib.Path) -> None:
+    """
+    This is a unit test that checks whether we called the GCS API
+    according to the expectations of this GCS mocking library:
+
+    https://github.com/odashi/cloud-storage-mocker
+
+    The library does not support mocks for all GCS operations,
+    and it is not maintained by the team that builds the GCS API.
+
+    If this test fails and it's unclear why,
+    run the integration tests to check our integration behavior for real
+    to see if something is wrong:
+
+    pytest -m integration
+    """
+
+    # Given the following mocked bucket
+    with gcs_patch(
+        [
+            Mount("testbucket", tmp_path / "src", readable=True, writable=True),
+        ],
+    ):
+        # When we do the steps to upload a file to mock GCS:
+        string_to_store = "Ada Lovelace"
+        timestamp = datetime.now().strftime("%Y-%m-%d-%H-%M-%S")
+        filename_to_store_it_at = f"first_computer_programmer_{timestamp}.txt"
+        encoded_string = string_to_store.encode(encoding='utf-8')
+
+        mock_client = google.cloud.storage.Client()
+        blob = mock_client.bucket("testbucket").blob(filename_to_store_it_at)
+        with io.BytesIO(encoded_string) as data:
+            blob.upload_from_file(data)
+
+        # Then Our API client is able to fetch them:
+        storage_client = CloudStorageAPIClient(project_name="testproject", bucket_name="testbucket")
+        storage_client.fetch(remote_path=filename_to_store_it_at, local_path=tmp_path / filename_to_store_it_at)
+        assert (tmp_path / filename_to_store_it_at).read_text() == string_to_store
+
+
+
diff --git a/tests/unit/test_example.py b/tests/unit/test_example.py
deleted file mode 100644
index 22be9ff..0000000
--- a/tests/unit/test_example.py
+++ /dev/null
@@ -1,6 +0,0 @@
-def test_example():
-    """
-    Example test for kicking off the unit test suite.
-    Used to check that pytest --ignore=tests/integration works as expected.
-    """
-    assert 1==1