Dockerfile, tests: fix typo, add backstop (#16309)

* Dockerfile, tests: fix typo, add backstop

Signed-off-by: William Woodruff <william@trailofbits.com>

* formatting, comment

Signed-off-by: William Woodruff <william@trailofbits.com>

---------

Signed-off-by: William Woodruff <william@trailofbits.com>

Dockerfile

@@ -232,7 +232,7 @@ RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
 # to keep these.
 RUN mkdir -p /tmp/share /tmp/cache
 ENV XDG_DATA_HOME /tmp/share
-ENV XDG_CACHE_COME /tmp/cache
+ENV XDG_CACHE_HOME /tmp/cache
 
 # Copy the directory into the container, this is done last so that changes to
 # Warehouse itself require the least amount of layers being invalidated from

tests/functional/test_environment.py

@@ -0,0 +1,22 @@
+# 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 platformdirs
+
+
+def test_xdg_environment():
+    # Backstop checks for Warehouse's (Dockerfile-configured) environment.
+    user_data = platformdirs.user_data_dir()
+    user_cache = platformdirs.user_cache_dir()
+
+    assert user_data == "/tmp/share"
+    assert user_cache == "/tmp/cache"