From 0e5bd06e591907d0f8a53840acddc38d7711b8c7 Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Sun, 26 Nov 2023 02:28:23 +0700
Subject: [PATCH 01/16] feat: add ability to define health check subsets

---
 health_check/backends.py |  6 +++---
 health_check/mixins.py   | 33 ++++++++++++++++++++++++++-------
 health_check/urls.py     |  1 +
 health_check/views.py    | 14 ++++++++------
 4 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/health_check/backends.py b/health_check/backends.py
index 36a46e71..11106b3f 100644
--- a/health_check/backends.py
+++ b/health_check/backends.py
@@ -20,14 +20,14 @@ class BaseHealthCheckBackend:
     def __init__(self):
         self.errors = []
 
-    def check_status(self):
+    def check_status(self, subset=None):
         raise NotImplementedError
 
-    def run_check(self):
+    def run_check(self, subset=None):
         start = timer()
         self.errors = []
         try:
-            self.check_status()
+            self.check_status(subset=subset)
         except HealthCheckException as e:
             self.add_error(e, e)
         except BaseException:
diff --git a/health_check/mixins.py b/health_check/mixins.py
index fefa29e9..3cdf5c4f 100644
--- a/health_check/mixins.py
+++ b/health_check/mixins.py
@@ -1,5 +1,8 @@
 import copy
+from collections import OrderedDict
 from concurrent.futures import ThreadPoolExecutor
+from django.conf import settings
+from django.http import Http404
 
 from health_check.conf import HEALTH_CHECK
 from health_check.exceptions import ServiceWarning
@@ -9,6 +12,7 @@
 class CheckMixin:
     _errors = None
     _plugins = None
+    _subset = None
 
     @property
     def errors(self):
@@ -16,19 +20,33 @@ def errors(self):
             self._errors = self.run_check()
         return self._errors
 
+    def check(self, subset):
+        return self.run_check(subset=subset)
+
     @property
     def plugins(self):
         if not self._plugins:
-            self._plugins = sorted(
-                (
+            registering_plugins = (
                     plugin_class(**copy.deepcopy(options))
                     for plugin_class, options in plugin_dir._registry
-                ),
-                key=lambda plugin: plugin.identifier(),
             )
+            self._plugins = OrderedDict({plugin.identifier(): plugin for plugin in registering_plugins})
         return self._plugins
 
-    def run_check(self):
+    def filter_plugins(self, subset=None):
+        if subset is None:
+            return self.plugins
+
+        health_check_subsets = getattr(settings, 'HEALTH_CHECK_SUBSETS', {})
+
+        if subset not in health_check_subsets:
+            raise Http404(f"Specify subset: '{subset}' does not exists.")
+
+        selected_subset = set(health_check_subsets[subset])
+        return {plugin_identifier: v for plugin_identifier, v in self.plugins.items() if plugin_identifier in selected_subset}
+
+
+    def run_check(self, subset=None):
         errors = []
 
         def _run(plugin):
@@ -40,8 +58,9 @@ def _run(plugin):
 
                 connections.close_all()
 
-        with ThreadPoolExecutor(max_workers=len(self.plugins) or 1) as executor:
-            for plugin in executor.map(_run, self.plugins):
+        plugins = self.filter_plugins(subset=subset)
+        with ThreadPoolExecutor(max_workers=len(plugins) or 1) as executor:
+            for plugin in executor.map(_run, plugins.values()):
                 if plugin.critical_service:
                     if not HEALTH_CHECK["WARNINGS_AS_ERRORS"]:
                         errors.extend(
diff --git a/health_check/urls.py b/health_check/urls.py
index 92bc7d65..416406be 100644
--- a/health_check/urls.py
+++ b/health_check/urls.py
@@ -6,4 +6,5 @@
 
 urlpatterns = [
     path("", MainView.as_view(), name="health_check_home"),
+    path("<str:subset>/", MainView.as_view(), name="health_check_subset"),
 ]
diff --git a/health_check/views.py b/health_check/views.py
index 8eadf912..75f9ad21 100644
--- a/health_check/views.py
+++ b/health_check/views.py
@@ -88,12 +88,13 @@ class MainView(CheckMixin, TemplateView):
 
     @method_decorator(never_cache)
     def get(self, request, *args, **kwargs):
-        status_code = 500 if self.errors else 200
-
+        subset = kwargs.get("subset", None)
+        health_check_has_error = self.check(subset)
+        status_code = 500 if health_check_has_error else 200
         format_override = request.GET.get("format")
 
         if format_override == "json":
-            return self.render_to_response_json(self.plugins, status_code)
+            return self.render_to_response_json(self.filter_plugins(subset=subset), status_code)
 
         accept_header = request.META.get("HTTP_ACCEPT", "*/*")
         for media in MediaType.parse_header(accept_header):
@@ -106,7 +107,7 @@ def get(self, request, *args, **kwargs):
                 context = self.get_context_data(**kwargs)
                 return self.render_to_response(context, status=status_code)
             elif media.mime_type in ("application/json", "application/*"):
-                return self.render_to_response_json(self.plugins, status_code)
+                return self.render_to_response_json(self.filter_plugins(subset=subset), status_code)
         return HttpResponse(
             "Not Acceptable: Supported content types: text/html, application/json",
             status=406,
@@ -114,10 +115,11 @@ def get(self, request, *args, **kwargs):
         )
 
     def get_context_data(self, **kwargs):
-        return {**super().get_context_data(**kwargs), "plugins": self.plugins}
+        subset = kwargs.get('subset', None)
+        return {**super().get_context_data(**kwargs), "plugins": self.filter_plugins(subset=subset).values()}
 
     def render_to_response_json(self, plugins, status):
         return JsonResponse(
-            {str(p.identifier()): str(p.pretty_status()) for p in plugins},
+            {str(plugin_identifier): str(p.pretty_status()) for plugin_identifier, p in plugins.items()},
             status=status,
         )

From 4c81186946a7c48984747ae9c706684fc0c371c8 Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Sun, 26 Nov 2023 02:29:19 +0700
Subject: [PATCH 02/16] feat: adjust default health check to conform with new
 structure

---
 health_check/cache/backends.py                   | 2 +-
 health_check/contrib/celery/backends.py          | 2 +-
 health_check/contrib/celery_ping/backends.py     | 2 +-
 health_check/contrib/migrations/backends.py      | 2 +-
 health_check/contrib/psutil/backends.py          | 4 ++--
 health_check/contrib/rabbitmq/backends.py        | 2 +-
 health_check/contrib/redis/backends.py           | 2 +-
 health_check/db/backends.py                      | 2 +-
 health_check/management/commands/health_check.py | 4 ++--
 health_check/storage/backends.py                 | 2 +-
 tests/test_commands.py                           | 4 ++--
 tests/test_mixins.py                             | 4 ++--
 tests/test_plugins.py                            | 4 ++--
 tests/test_views.py                              | 6 +++---
 14 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/health_check/cache/backends.py b/health_check/cache/backends.py
index d810f805..6b6c050c 100644
--- a/health_check/cache/backends.py
+++ b/health_check/cache/backends.py
@@ -28,7 +28,7 @@ def __init__(self, backend="default"):
     def identifier(self):
         return f"Cache backend: {self.backend}"
 
-    def check_status(self):
+    def check_status(self, subset=None):
         cache = caches[self.backend]
 
         try:
diff --git a/health_check/contrib/celery/backends.py b/health_check/contrib/celery/backends.py
index 77afbdc5..7454597e 100644
--- a/health_check/contrib/celery/backends.py
+++ b/health_check/contrib/celery/backends.py
@@ -8,7 +8,7 @@
 
 
 class CeleryHealthCheck(BaseHealthCheckBackend):
-    def check_status(self):
+    def check_status(self, subset=None):
         timeout = getattr(settings, "HEALTHCHECK_CELERY_TIMEOUT", 3)
         result_timeout = getattr(settings, "HEALTHCHECK_CELERY_RESULT_TIMEOUT", timeout)
         queue_timeout = getattr(settings, "HEALTHCHECK_CELERY_QUEUE_TIMEOUT", timeout)
diff --git a/health_check/contrib/celery_ping/backends.py b/health_check/contrib/celery_ping/backends.py
index 4c2a2d34..2fdc9a69 100644
--- a/health_check/contrib/celery_ping/backends.py
+++ b/health_check/contrib/celery_ping/backends.py
@@ -8,7 +8,7 @@
 class CeleryPingHealthCheck(BaseHealthCheckBackend):
     CORRECT_PING_RESPONSE = {"ok": "pong"}
 
-    def check_status(self):
+    def check_status(self, subset=None):
         timeout = getattr(settings, "HEALTHCHECK_CELERY_PING_TIMEOUT", 1)
 
         try:
diff --git a/health_check/contrib/migrations/backends.py b/health_check/contrib/migrations/backends.py
index 727b1814..c465c8f2 100644
--- a/health_check/contrib/migrations/backends.py
+++ b/health_check/contrib/migrations/backends.py
@@ -14,7 +14,7 @@ class MigrationsHealthCheck(BaseHealthCheckBackend):
     def get_migration_plan(self, executor):
         return executor.migration_plan(executor.loader.graph.leaf_nodes())
 
-    def check_status(self):
+    def check_status(self, subset=None):
         db_alias = getattr(settings, "HEALTHCHECK_MIGRATIONS_DB", DEFAULT_DB_ALIAS)
         try:
             executor = MigrationExecutor(connections[db_alias])
diff --git a/health_check/contrib/psutil/backends.py b/health_check/contrib/psutil/backends.py
index 0d2709a4..d5054ec6 100644
--- a/health_check/contrib/psutil/backends.py
+++ b/health_check/contrib/psutil/backends.py
@@ -14,7 +14,7 @@
 
 
 class DiskUsage(BaseHealthCheckBackend):
-    def check_status(self):
+    def check_status(self, subset=None):
         try:
             du = psutil.disk_usage("/")
             if DISK_USAGE_MAX and du.percent >= DISK_USAGE_MAX:
@@ -28,7 +28,7 @@ def check_status(self):
 
 
 class MemoryUsage(BaseHealthCheckBackend):
-    def check_status(self):
+    def check_status(self, subset=None):
         try:
             memory = psutil.virtual_memory()
             if MEMORY_MIN and memory.available < (MEMORY_MIN * 1024 * 1024):
diff --git a/health_check/contrib/rabbitmq/backends.py b/health_check/contrib/rabbitmq/backends.py
index adaff36b..37c9f9dc 100644
--- a/health_check/contrib/rabbitmq/backends.py
+++ b/health_check/contrib/rabbitmq/backends.py
@@ -15,7 +15,7 @@ class RabbitMQHealthCheck(BaseHealthCheckBackend):
 
     namespace = None
 
-    def check_status(self):
+    def check_status(self, subset=None):
         """Check RabbitMQ service by opening and closing a broker channel."""
         logger.debug("Checking for a broker_url on django settings...")
 
diff --git a/health_check/contrib/redis/backends.py b/health_check/contrib/redis/backends.py
index 9d7272c6..e9076bbf 100644
--- a/health_check/contrib/redis/backends.py
+++ b/health_check/contrib/redis/backends.py
@@ -14,7 +14,7 @@ class RedisHealthCheck(BaseHealthCheckBackend):
 
     redis_url = getattr(settings, "REDIS_URL", "redis://localhost/1")
 
-    def check_status(self):
+    def check_status(self, subset=None):
         """Check Redis service by pinging the redis instance with a redis connection."""
         logger.debug("Got %s as the redis_url. Connecting to redis...", self.redis_url)
 
diff --git a/health_check/db/backends.py b/health_check/db/backends.py
index 8687d994..1c7473fd 100644
--- a/health_check/db/backends.py
+++ b/health_check/db/backends.py
@@ -7,7 +7,7 @@
 
 
 class DatabaseBackend(BaseHealthCheckBackend):
-    def check_status(self):
+    def check_status(self, subset=None):
         try:
             obj = TestModel.objects.create(title="test")
             obj.title = "newtest"
diff --git a/health_check/management/commands/health_check.py b/health_check/management/commands/health_check.py
index 1bb7e723..22a4f6ae 100644
--- a/health_check/management/commands/health_check.py
+++ b/health_check/management/commands/health_check.py
@@ -12,11 +12,11 @@ def handle(self, *args, **options):
         # perform all checks
         errors = self.errors
 
-        for plugin in self.plugins:
+        for plugin_identifier, plugin in self.plugins.items():
             style_func = self.style.SUCCESS if not plugin.errors else self.style.ERROR
             self.stdout.write(
                 "{:<24} ... {}\n".format(
-                    plugin.identifier(), style_func(plugin.pretty_status())
+                    plugin_identifier, style_func(plugin.pretty_status())
                 )
             )
 
diff --git a/health_check/storage/backends.py b/health_check/storage/backends.py
index 5920b133..0d966d67 100644
--- a/health_check/storage/backends.py
+++ b/health_check/storage/backends.py
@@ -67,7 +67,7 @@ def check_delete(self, file_name):
         if storage.exists(file_name):
             raise ServiceUnavailable("File was not deleted")
 
-    def check_status(self):
+    def check_status(self, subset=None):
         try:
             # write the file to the storage backend
             file_name = self.get_file_name()
diff --git a/tests/test_commands.py b/tests/test_commands.py
index 59c0ceb2..a4ad47ae 100644
--- a/tests/test_commands.py
+++ b/tests/test_commands.py
@@ -8,12 +8,12 @@
 
 
 class FailPlugin(BaseHealthCheckBackend):
-    def check_status(self):
+    def check_status(self, subset=None):
         self.add_error("Oops")
 
 
 class OkPlugin(BaseHealthCheckBackend):
-    def check_status(self):
+    def check_status(self, subset=None):
         pass
 
 
diff --git a/tests/test_mixins.py b/tests/test_mixins.py
index 1a35e936..2393490c 100644
--- a/tests/test_mixins.py
+++ b/tests/test_mixins.py
@@ -6,12 +6,12 @@
 
 
 class FailPlugin(BaseHealthCheckBackend):
-    def check_status(self):
+    def check_status(self, subset=None):
         self.add_error("Oops")
 
 
 class OkPlugin(BaseHealthCheckBackend):
-    def check_status(self):
+    def check_status(self, subset=None):
         pass
 
 
diff --git a/tests/test_plugins.py b/tests/test_plugins.py
index 879d4b9d..d2ad270c 100644
--- a/tests/test_plugins.py
+++ b/tests/test_plugins.py
@@ -5,12 +5,12 @@
 
 
 class FakePlugin(BaseHealthCheckBackend):
-    def check_status(self):
+    def check_status(self, subset=None):
         pass
 
 
 class Plugin(BaseHealthCheckBackend):
-    def check_status(self):
+    def check_status(self, subset=None):
         pass
 
 
diff --git a/tests/test_views.py b/tests/test_views.py
index 252e76c9..a0a60f77 100644
--- a/tests/test_views.py
+++ b/tests/test_views.py
@@ -92,7 +92,7 @@ def test_success(self, client):
 
     def test_error(self, client):
         class MyBackend(BaseHealthCheckBackend):
-            def check_status(self):
+            def check_status(self, subset=None):
                 self.add_error("Super Fail!")
 
         plugin_dir.reset()
@@ -104,7 +104,7 @@ def check_status(self):
 
     def test_warning(self, client):
         class MyBackend(BaseHealthCheckBackend):
-            def check_status(self):
+            def check_status(self, subset=None):
                 raise ServiceWarning("so so")
 
         plugin_dir.reset()
@@ -124,7 +124,7 @@ def test_non_critical(self, client):
         class MyBackend(BaseHealthCheckBackend):
             critical_service = False
 
-            def check_status(self):
+            def check_status(self, subset=None):
                 self.add_error("Super Fail!")
 
         plugin_dir.reset()

From 51c6ed84b352f0b1745be82ba7feb5c3646d6b7a Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Sun, 26 Nov 2023 02:42:51 +0700
Subject: [PATCH 03/16] chore: add usage instruction in readme

---
 README.md | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/README.md b/README.md
index ffba6438..71d01e26 100644
--- a/README.md
+++ b/README.md
@@ -90,6 +90,19 @@ one of these checks, set its value to `None`.
     }
 ```
 
+To use Health Check Subsets, Specify a subset name and associate it with the relevant health check services to utilize Health Check Subsets.
+```python
+    HEALTH_CHECK_SUBSETS = {
+        'startup-probe': ['DatabaseBackend', 'MigrationsHealthCheck'],
+        'liveness-probe': ['DatabaseBackend'],
+    }
+```
+
+To only execute specific subset of health check
+```shell
+curl -X GET -H "Accept: application/json" http://www.example.com/ht/startup-probe/
+```
+
 If using the DB check, run migrations:
 
 ```shell

From 0e5cd5f375920214a88ea2157a32ac69b6cccaaa Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Sun, 26 Nov 2023 03:02:18 +0700
Subject: [PATCH 04/16] feat: allow subset argument to be specify using Django
 Command

---
 health_check/management/commands/health_check.py | 9 +++++++--
 health_check/mixins.py                           | 2 +-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/health_check/management/commands/health_check.py b/health_check/management/commands/health_check.py
index 22a4f6ae..541ea209 100644
--- a/health_check/management/commands/health_check.py
+++ b/health_check/management/commands/health_check.py
@@ -8,11 +8,16 @@
 class Command(CheckMixin, BaseCommand):
     help = "Run health checks and exit 0 if everything went well."
 
+    def add_arguments(self, parser):
+        parser.add_argument("--subset", type=str, default=None, nargs=1)
+
     def handle(self, *args, **options):
         # perform all checks
-        errors = self.errors
+        subset = options.get("subset", [])
+        subset = subset[0] if subset else None
+        errors = self.check(subset=subset)
 
-        for plugin_identifier, plugin in self.plugins.items():
+        for plugin_identifier, plugin in self.filter_plugins(subset=subset).items():
             style_func = self.style.SUCCESS if not plugin.errors else self.style.ERROR
             self.stdout.write(
                 "{:<24} ... {}\n".format(
diff --git a/health_check/mixins.py b/health_check/mixins.py
index 3cdf5c4f..bfbf30a7 100644
--- a/health_check/mixins.py
+++ b/health_check/mixins.py
@@ -20,7 +20,7 @@ def errors(self):
             self._errors = self.run_check()
         return self._errors
 
-    def check(self, subset):
+    def check(self, subset=None):
         return self.run_check(subset=subset)
 
     @property

From 77fba53fedea3ff15094e55611ff578078070b47 Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Sun, 26 Nov 2023 03:17:30 +0700
Subject: [PATCH 05/16] feat: fix broken tests with missing subset argument

---
 tests/test_views.py | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/tests/test_views.py b/tests/test_views.py
index a0a60f77..cc8e86c6 100644
--- a/tests/test_views.py
+++ b/tests/test_views.py
@@ -136,7 +136,7 @@ def check_status(self, subset=None):
 
     def test_success_accept_json(self, client):
         class JSONSuccessBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 pass
 
         plugin_dir.reset()
@@ -147,7 +147,7 @@ def run_check(self):
 
     def test_success_prefer_json(self, client):
         class JSONSuccessBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 pass
 
         plugin_dir.reset()
@@ -160,7 +160,7 @@ def run_check(self):
 
     def test_success_accept_xhtml(self, client):
         class SuccessBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 pass
 
         plugin_dir.reset()
@@ -171,7 +171,7 @@ def run_check(self):
 
     def test_success_unsupported_accept(self, client):
         class SuccessBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 pass
 
         plugin_dir.reset()
@@ -186,7 +186,7 @@ def run_check(self):
 
     def test_success_unsupported_and_supported_accept(self, client):
         class SuccessBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 pass
 
         plugin_dir.reset()
@@ -199,7 +199,7 @@ def run_check(self):
 
     def test_success_accept_order(self, client):
         class JSONSuccessBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 pass
 
         plugin_dir.reset()
@@ -213,7 +213,7 @@ def run_check(self):
 
     def test_success_accept_order__reverse(self, client):
         class JSONSuccessBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 pass
 
         plugin_dir.reset()
@@ -227,7 +227,7 @@ def run_check(self):
 
     def test_format_override(self, client):
         class JSONSuccessBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 pass
 
         plugin_dir.reset()
@@ -238,7 +238,7 @@ def run_check(self):
 
     def test_format_no_accept_header(self, client):
         class JSONSuccessBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 pass
 
         plugin_dir.reset()
@@ -249,7 +249,7 @@ def run_check(self):
 
     def test_error_accept_json(self, client):
         class JSONErrorBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 self.add_error("JSON Error")
 
         plugin_dir.reset()
@@ -266,7 +266,7 @@ def run_check(self):
 
     def test_success_param_json(self, client):
         class JSONSuccessBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 pass
 
         plugin_dir.reset()
@@ -278,9 +278,13 @@ def run_check(self):
             JSONSuccessBackend().identifier(): JSONSuccessBackend().pretty_status()
         }
 
+
+    def test_success_subset_define(self, client):
+
+
     def test_error_param_json(self, client):
         class JSONErrorBackend(BaseHealthCheckBackend):
-            def run_check(self):
+            def run_check(self, subset=None):
                 self.add_error("JSON Error")
 
         plugin_dir.reset()

From 4268859ddc74ab555158a9c1ae279f486678f9d7 Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Sun, 26 Nov 2023 03:22:29 +0700
Subject: [PATCH 06/16] feat: move getattr from django settings to conf

---
 health_check/conf.py   | 1 +
 health_check/mixins.py | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/health_check/conf.py b/health_check/conf.py
index fdd2b1ec..ab72ed0e 100644
--- a/health_check/conf.py
+++ b/health_check/conf.py
@@ -4,3 +4,4 @@
 HEALTH_CHECK.setdefault("DISK_USAGE_MAX", 90)
 HEALTH_CHECK.setdefault("MEMORY_MIN", 100)
 HEALTH_CHECK.setdefault("WARNINGS_AS_ERRORS", True)
+HEALTH_CHECK_SUBSETS = getattr(settings, "HEALTH_CHECK_SUBSETS", {})
diff --git a/health_check/mixins.py b/health_check/mixins.py
index bfbf30a7..b775f6e3 100644
--- a/health_check/mixins.py
+++ b/health_check/mixins.py
@@ -4,7 +4,7 @@
 from django.conf import settings
 from django.http import Http404
 
-from health_check.conf import HEALTH_CHECK
+from health_check.conf import HEALTH_CHECK, HEALTH_CHECK_SUBSETS
 from health_check.exceptions import ServiceWarning
 from health_check.plugins import plugin_dir
 
@@ -37,7 +37,7 @@ def filter_plugins(self, subset=None):
         if subset is None:
             return self.plugins
 
-        health_check_subsets = getattr(settings, 'HEALTH_CHECK_SUBSETS', {})
+        health_check_subsets = HEALTH_CHECK_SUBSETS
 
         if subset not in health_check_subsets:
             raise Http404(f"Specify subset: '{subset}' does not exists.")

From afc83476baffdf11f07de1ae8fe51ef0399821e7 Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Sun, 26 Nov 2023 03:26:21 +0700
Subject: [PATCH 07/16] feat: remove unused variable

---
 health_check/mixins.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/health_check/mixins.py b/health_check/mixins.py
index b775f6e3..6d43f57d 100644
--- a/health_check/mixins.py
+++ b/health_check/mixins.py
@@ -1,7 +1,6 @@
 import copy
 from collections import OrderedDict
 from concurrent.futures import ThreadPoolExecutor
-from django.conf import settings
 from django.http import Http404
 
 from health_check.conf import HEALTH_CHECK, HEALTH_CHECK_SUBSETS
@@ -12,7 +11,6 @@
 class CheckMixin:
     _errors = None
     _plugins = None
-    _subset = None
 
     @property
     def errors(self):

From 5d248d713f6b31bebdbc84897bb4a1a065e8f785 Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Sun, 26 Nov 2023 03:36:54 +0700
Subject: [PATCH 08/16] feat: add tests

---
 health_check/mixins.py | 16 +++++++++++-----
 health_check/views.py  | 20 +++++++++++++++-----
 tests/test_views.py    | 41 ++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 66 insertions(+), 11 deletions(-)

diff --git a/health_check/mixins.py b/health_check/mixins.py
index 6d43f57d..c808a4d2 100644
--- a/health_check/mixins.py
+++ b/health_check/mixins.py
@@ -1,6 +1,7 @@
 import copy
 from collections import OrderedDict
 from concurrent.futures import ThreadPoolExecutor
+
 from django.http import Http404
 
 from health_check.conf import HEALTH_CHECK, HEALTH_CHECK_SUBSETS
@@ -25,10 +26,12 @@ def check(self, subset=None):
     def plugins(self):
         if not self._plugins:
             registering_plugins = (
-                    plugin_class(**copy.deepcopy(options))
-                    for plugin_class, options in plugin_dir._registry
+                plugin_class(**copy.deepcopy(options))
+                for plugin_class, options in plugin_dir._registry
+            )
+            self._plugins = OrderedDict(
+                {plugin.identifier(): plugin for plugin in registering_plugins}
             )
-            self._plugins = OrderedDict({plugin.identifier(): plugin for plugin in registering_plugins})
         return self._plugins
 
     def filter_plugins(self, subset=None):
@@ -41,8 +44,11 @@ def filter_plugins(self, subset=None):
             raise Http404(f"Specify subset: '{subset}' does not exists.")
 
         selected_subset = set(health_check_subsets[subset])
-        return {plugin_identifier: v for plugin_identifier, v in self.plugins.items() if plugin_identifier in selected_subset}
-
+        return {
+            plugin_identifier: v
+            for plugin_identifier, v in self.plugins.items()
+            if plugin_identifier in selected_subset
+        }
 
     def run_check(self, subset=None):
         errors = []
diff --git a/health_check/views.py b/health_check/views.py
index 75f9ad21..3c928e90 100644
--- a/health_check/views.py
+++ b/health_check/views.py
@@ -94,7 +94,9 @@ def get(self, request, *args, **kwargs):
         format_override = request.GET.get("format")
 
         if format_override == "json":
-            return self.render_to_response_json(self.filter_plugins(subset=subset), status_code)
+            return self.render_to_response_json(
+                self.filter_plugins(subset=subset), status_code
+            )
 
         accept_header = request.META.get("HTTP_ACCEPT", "*/*")
         for media in MediaType.parse_header(accept_header):
@@ -107,7 +109,9 @@ def get(self, request, *args, **kwargs):
                 context = self.get_context_data(**kwargs)
                 return self.render_to_response(context, status=status_code)
             elif media.mime_type in ("application/json", "application/*"):
-                return self.render_to_response_json(self.filter_plugins(subset=subset), status_code)
+                return self.render_to_response_json(
+                    self.filter_plugins(subset=subset), status_code
+                )
         return HttpResponse(
             "Not Acceptable: Supported content types: text/html, application/json",
             status=406,
@@ -115,11 +119,17 @@ def get(self, request, *args, **kwargs):
         )
 
     def get_context_data(self, **kwargs):
-        subset = kwargs.get('subset', None)
-        return {**super().get_context_data(**kwargs), "plugins": self.filter_plugins(subset=subset).values()}
+        subset = kwargs.get("subset", None)
+        return {
+            **super().get_context_data(**kwargs),
+            "plugins": self.filter_plugins(subset=subset).values(),
+        }
 
     def render_to_response_json(self, plugins, status):
         return JsonResponse(
-            {str(plugin_identifier): str(p.pretty_status()) for plugin_identifier, p in plugins.items()},
+            {
+                str(plugin_identifier): str(p.pretty_status())
+                for plugin_identifier, p in plugins.items()
+            },
             status=status,
         )
diff --git a/tests/test_views.py b/tests/test_views.py
index cc8e86c6..92f4834b 100644
--- a/tests/test_views.py
+++ b/tests/test_views.py
@@ -2,6 +2,7 @@
 
 import pytest
 
+from health_check import conf
 from health_check.backends import BaseHealthCheckBackend
 from health_check.conf import HEALTH_CHECK
 from health_check.exceptions import ServiceWarning
@@ -278,9 +279,47 @@ def run_check(self, subset=None):
             JSONSuccessBackend().identifier(): JSONSuccessBackend().pretty_status()
         }
 
-
     def test_success_subset_define(self, client):
+        class SuccessOneBackend(BaseHealthCheckBackend):
+            def run_check(self, subset=None):
+                pass
 
+        class SuccessTwoBackend(BaseHealthCheckBackend):
+            def run_check(self, subset=None):
+                pass
+
+        plugin_dir.reset()
+        plugin_dir.register(SuccessOneBackend)
+        plugin_dir.register(SuccessTwoBackend)
+
+        HEALTH_CHECK_SUBSETS = {
+            "startup-probe": ["SuccessOneBackend", "SuccessTwoBackend"],
+            "liveness-probe": ["SuccessTwoBackend"],
+        }
+        setattr(conf, "HEALTH_CHECK_SUBSETS", HEALTH_CHECK_SUBSETS)
+
+        response_startup_probe = client.get(
+            self.url + "startup-probe/", {"format": "json"}
+        )
+        assert (
+            response_startup_probe.status_code == 200
+        ), response_startup_probe.content.decode("utf-8")
+        assert response_startup_probe["content-type"] == "application/json"
+        assert json.loads(response_startup_probe.content.decode("utf-8")) == {
+            SuccessOneBackend().identifier(): SuccessOneBackend().pretty_status(),
+            SuccessTwoBackend().identifier(): SuccessTwoBackend().pretty_status(),
+        }
+
+        response_liveness_probe = client.get(
+            self.url + "liveness-probe/", {"format": "json"}
+        )
+        assert (
+            response_liveness_probe.status_code == 200
+        ), response_liveness_probe.content.decode("utf-8")
+        assert response_liveness_probe["content-type"] == "application/json"
+        assert json.loads(response_liveness_probe.content.decode("utf-8")) == {
+            SuccessTwoBackend().identifier(): SuccessTwoBackend().pretty_status(),
+        }
 
     def test_error_param_json(self, client):
         class JSONErrorBackend(BaseHealthCheckBackend):

From b61c4f1e1320af6cf8b8e06edaf6a7874099931c Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Sun, 26 Nov 2023 03:45:26 +0700
Subject: [PATCH 09/16] feat: add subset not found should return HTTP 404

---
 tests/test_views.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tests/test_views.py b/tests/test_views.py
index 92f4834b..2b861701 100644
--- a/tests/test_views.py
+++ b/tests/test_views.py
@@ -321,6 +321,10 @@ def run_check(self, subset=None):
             SuccessTwoBackend().identifier(): SuccessTwoBackend().pretty_status(),
         }
 
+    def test_error_subset_not_found(self, client):
+        response = client.get(self.url, {"format": "json"})
+        assert response.status_code == 404, response.content.decode("utf-8")
+
     def test_error_param_json(self, client):
         class JSONErrorBackend(BaseHealthCheckBackend):
             def run_check(self, subset=None):

From 99ae3952be249df2a82f3111ec890d81f1d8aeef Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Sun, 26 Nov 2023 12:59:44 +0700
Subject: [PATCH 10/16] feat: ensure plugins are sorted by name

---
 health_check/mixins.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/health_check/mixins.py b/health_check/mixins.py
index c808a4d2..a498f848 100644
--- a/health_check/mixins.py
+++ b/health_check/mixins.py
@@ -29,6 +29,7 @@ def plugins(self):
                 plugin_class(**copy.deepcopy(options))
                 for plugin_class, options in plugin_dir._registry
             )
+            registering_plugins = sorted(registering_plugins, key=lambda plugin: plugin.identifier())
             self._plugins = OrderedDict(
                 {plugin.identifier(): plugin for plugin in registering_plugins}
             )

From 01364bddb9d26202f0defebb60a90030311f85a4 Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Sun, 26 Nov 2023 13:01:11 +0700
Subject: [PATCH 11/16] feat: ensure plugins are sorted by name

---
 health_check/mixins.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/health_check/mixins.py b/health_check/mixins.py
index a498f848..eeb55153 100644
--- a/health_check/mixins.py
+++ b/health_check/mixins.py
@@ -29,7 +29,9 @@ def plugins(self):
                 plugin_class(**copy.deepcopy(options))
                 for plugin_class, options in plugin_dir._registry
             )
-            registering_plugins = sorted(registering_plugins, key=lambda plugin: plugin.identifier())
+            registering_plugins = sorted(
+                registering_plugins, key=lambda plugin: plugin.identifier()
+            )
             self._plugins = OrderedDict(
                 {plugin.identifier(): plugin for plugin in registering_plugins}
             )

From 1aa13e7ffe3abe0bb6277ec1c03143a420f463b0 Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Mon, 27 Nov 2023 15:22:31 +0700
Subject: [PATCH 12/16] feat: adjust health check config structure

---
 README.md            | 11 ++++++++---
 health_check/conf.py |  4 +++-
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 71d01e26..b95f2b44 100644
--- a/README.md
+++ b/README.md
@@ -92,9 +92,14 @@ one of these checks, set its value to `None`.
 
 To use Health Check Subsets, Specify a subset name and associate it with the relevant health check services to utilize Health Check Subsets.
 ```python
-    HEALTH_CHECK_SUBSETS = {
-        'startup-probe': ['DatabaseBackend', 'MigrationsHealthCheck'],
-        'liveness-probe': ['DatabaseBackend'],
+    HEALTH_CHECK = {
+        # .....
+        "SUBSETS": {
+            "startup-probe": ["MigrationsHealthCheck", "DatabaseBackend"],
+            "liveness-probe": ["DatabaseBackend"],
+            "<SUBSET_NAME>": ["<Health_Check_Service_Name"]
+        },
+        # .....
     }
 ```
 
diff --git a/health_check/conf.py b/health_check/conf.py
index ab72ed0e..9eeb8b9e 100644
--- a/health_check/conf.py
+++ b/health_check/conf.py
@@ -4,4 +4,6 @@
 HEALTH_CHECK.setdefault("DISK_USAGE_MAX", 90)
 HEALTH_CHECK.setdefault("MEMORY_MIN", 100)
 HEALTH_CHECK.setdefault("WARNINGS_AS_ERRORS", True)
-HEALTH_CHECK_SUBSETS = getattr(settings, "HEALTH_CHECK_SUBSETS", {})
+HEALTH_CHECK.setdefault("SUBSETS", {})
+
+HEALTH_CHECK_SUBSETS = HEALTH_CHECK.get("SUBSETS")

From bd690fc357453a3e5edc1aa99ab90a4af90518c6 Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Wed, 29 Nov 2023 12:10:08 +0700
Subject: [PATCH 13/16] feat: add more tests

---
 health_check/conf.py   |  2 --
 health_check/mixins.py | 10 ++++++----
 tests/test_views.py    |  8 +++++---
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/health_check/conf.py b/health_check/conf.py
index 9eeb8b9e..adb74e17 100644
--- a/health_check/conf.py
+++ b/health_check/conf.py
@@ -5,5 +5,3 @@
 HEALTH_CHECK.setdefault("MEMORY_MIN", 100)
 HEALTH_CHECK.setdefault("WARNINGS_AS_ERRORS", True)
 HEALTH_CHECK.setdefault("SUBSETS", {})
-
-HEALTH_CHECK_SUBSETS = HEALTH_CHECK.get("SUBSETS")
diff --git a/health_check/mixins.py b/health_check/mixins.py
index eeb55153..c6a6d704 100644
--- a/health_check/mixins.py
+++ b/health_check/mixins.py
@@ -4,7 +4,7 @@
 
 from django.http import Http404
 
-from health_check.conf import HEALTH_CHECK, HEALTH_CHECK_SUBSETS
+from health_check.conf import HEALTH_CHECK
 from health_check.exceptions import ServiceWarning
 from health_check.plugins import plugin_dir
 
@@ -24,6 +24,9 @@ def check(self, subset=None):
 
     @property
     def plugins(self):
+        if not plugin_dir._registry:
+            return OrderedDict({})
+
         if not self._plugins:
             registering_plugins = (
                 plugin_class(**copy.deepcopy(options))
@@ -41,9 +44,8 @@ def filter_plugins(self, subset=None):
         if subset is None:
             return self.plugins
 
-        health_check_subsets = HEALTH_CHECK_SUBSETS
-
-        if subset not in health_check_subsets:
+        health_check_subsets = HEALTH_CHECK['SUBSETS']
+        if subset not in health_check_subsets or not self.plugins:
             raise Http404(f"Specify subset: '{subset}' does not exists.")
 
         selected_subset = set(health_check_subsets[subset])
diff --git a/tests/test_views.py b/tests/test_views.py
index 2b861701..61047a29 100644
--- a/tests/test_views.py
+++ b/tests/test_views.py
@@ -292,11 +292,10 @@ def run_check(self, subset=None):
         plugin_dir.register(SuccessOneBackend)
         plugin_dir.register(SuccessTwoBackend)
 
-        HEALTH_CHECK_SUBSETS = {
+        HEALTH_CHECK['SUBSETS'] = {
             "startup-probe": ["SuccessOneBackend", "SuccessTwoBackend"],
             "liveness-probe": ["SuccessTwoBackend"],
         }
-        setattr(conf, "HEALTH_CHECK_SUBSETS", HEALTH_CHECK_SUBSETS)
 
         response_startup_probe = client.get(
             self.url + "startup-probe/", {"format": "json"}
@@ -322,7 +321,10 @@ def run_check(self, subset=None):
         }
 
     def test_error_subset_not_found(self, client):
-        response = client.get(self.url, {"format": "json"})
+        plugin_dir.reset()
+        response = client.get(self.url + "liveness-probe/", {"format": "json"})
+        print(f"content: {response.content}")
+        print(f"code: {response.status_code}")
         assert response.status_code == 404, response.content.decode("utf-8")
 
     def test_error_param_json(self, client):

From ad0b1e8b263a150dacc6f77896d8b10789028dcb Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Wed, 29 Nov 2023 12:41:04 +0700
Subject: [PATCH 14/16] feat: add commmand tests

---
 .../management/commands/health_check.py       |  9 +++-
 tests/test_commands.py                        | 47 +++++++++++++++++++
 2 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/health_check/management/commands/health_check.py b/health_check/management/commands/health_check.py
index 541ea209..eb36ac88 100644
--- a/health_check/management/commands/health_check.py
+++ b/health_check/management/commands/health_check.py
@@ -1,6 +1,7 @@
 import sys
 
 from django.core.management.base import BaseCommand
+from django.http import Http404
 
 from health_check.mixins import CheckMixin
 
@@ -9,13 +10,17 @@ class Command(CheckMixin, BaseCommand):
     help = "Run health checks and exit 0 if everything went well."
 
     def add_arguments(self, parser):
-        parser.add_argument("--subset", type=str, default=None, nargs=1)
+        parser.add_argument("-s", '--subset', type=str, nargs=1)
 
     def handle(self, *args, **options):
         # perform all checks
         subset = options.get("subset", [])
         subset = subset[0] if subset else None
-        errors = self.check(subset=subset)
+        try:
+            errors = self.check(subset=subset)
+        except Http404 as e:
+            self.stdout.write(str(e))
+            sys.exit(1)
 
         for plugin_identifier, plugin in self.filter_plugins(subset=subset).items():
             style_func = self.style.SUCCESS if not plugin.errors else self.style.ERROR
diff --git a/tests/test_commands.py b/tests/test_commands.py
index a4ad47ae..7c7aaf15 100644
--- a/tests/test_commands.py
+++ b/tests/test_commands.py
@@ -4,6 +4,7 @@
 from django.core.management import call_command
 
 from health_check.backends import BaseHealthCheckBackend
+from health_check.conf import HEALTH_CHECK
 from health_check.plugins import plugin_dir
 
 
@@ -35,3 +36,49 @@ def test_command(self):
             "FailPlugin               ... unknown error: Oops\n"
             "OkPlugin                 ... working\n"
         )
+
+    def test_command_with_subset(self):
+        SUBSET_NAME_1 = 'subset-1'
+        SUBSET_NAME_2 = 'subset-2'
+        HEALTH_CHECK['SUBSETS'] = {
+            SUBSET_NAME_1: ["OkPlugin"],
+            SUBSET_NAME_2: ["OkPlugin", "FailPlugin"]
+        }
+
+        stdout = StringIO()
+        call_command(f"health_check", f"--subset={SUBSET_NAME_1}", stdout=stdout)
+        stdout.seek(0)
+        assert stdout.read() == (
+            "OkPlugin                 ... working\n"
+        )
+
+
+    def test_command_with_failed_check_subset(self):
+        SUBSET_NAME = 'subset-2'
+        HEALTH_CHECK['SUBSETS'] = {
+            SUBSET_NAME: ["OkPlugin", "FailPlugin"]
+        }
+
+        stdout = StringIO()
+        with pytest.raises(SystemExit):
+            call_command(f"health_check", f"--subset={SUBSET_NAME}", stdout=stdout)
+        stdout.seek(0)
+        assert stdout.read() == (
+            "FailPlugin               ... unknown error: Oops\n"
+            "OkPlugin                 ... working\n"
+        )
+
+    def test_command_with_non_existence_subset(self):
+        SUBSET_NAME = 'subset-2'
+        NON_EXISTENCE_SUBSET_NAME = "abcdef12"
+        HEALTH_CHECK['SUBSETS'] = {
+            SUBSET_NAME: ["OkPlugin"]
+        }
+
+        stdout = StringIO()
+        with pytest.raises(SystemExit):
+            call_command(f"health_check", f"--subset={NON_EXISTENCE_SUBSET_NAME}", stdout=stdout)
+        stdout.seek(0)
+        assert stdout.read() == (
+            f"Specify subset: '{NON_EXISTENCE_SUBSET_NAME}' does not exists.\n"
+        )

From 649274160128647fb1e44c663661bd9e3e4a2473 Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Wed, 13 Dec 2023 23:50:23 +0700
Subject: [PATCH 15/16] feat: fix merge conflicts

---
 health_check/mixins.py | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/health_check/mixins.py b/health_check/mixins.py
index ac87939b..e32be97e 100644
--- a/health_check/mixins.py
+++ b/health_check/mixins.py
@@ -66,7 +66,7 @@ def _run(plugin):
                 from django.db import connections
 
                 connections.close_all()
-        
+
         def _collect_errors(plugin):
             if plugin.critical_service:
                 if not HEALTH_CHECK["WARNINGS_AS_ERRORS"]:
@@ -75,15 +75,16 @@ def _collect_errors(plugin):
                     )
                 else:
                     errors.extend(plugin.errors)
-                    
+
         plugins = self.filter_plugins(subset=subset)
-        
+        plugin_instances = plugins.values()
+
         if HEALTH_CHECK["DISABLE_THREADING"]:
-            for plugin in plugins:
+            for plugin in plugin_instances:
                 _run(plugin)
                 _collect_errors(plugin)
         else:
-            with ThreadPoolExecutor(max_workers=len(plugins) or 1) as executor:
-                for plugin in executor.map(_run, plugins):
+            with ThreadPoolExecutor(max_workers=len(plugin_instances) or 1) as executor:
+                for plugin in executor.map(_run, plugin_instances):
                     _collect_errors(plugin)
         return errors

From 13efe1a19af34edfd5fa08efe32ea6f778f25687 Mon Sep 17 00:00:00 2001
From: Pan Teparak <panteparak@me.com>
Date: Wed, 13 Dec 2023 23:51:44 +0700
Subject: [PATCH 16/16] feat: fix merge conflicts

---
 .../management/commands/health_check.py       |  2 +-
 health_check/mixins.py                        |  2 +-
 tests/test_commands.py                        | 33 ++++++++-----------
 tests/test_views.py                           |  3 +-
 4 files changed, 17 insertions(+), 23 deletions(-)

diff --git a/health_check/management/commands/health_check.py b/health_check/management/commands/health_check.py
index eb36ac88..191d50d1 100644
--- a/health_check/management/commands/health_check.py
+++ b/health_check/management/commands/health_check.py
@@ -10,7 +10,7 @@ class Command(CheckMixin, BaseCommand):
     help = "Run health checks and exit 0 if everything went well."
 
     def add_arguments(self, parser):
-        parser.add_argument("-s", '--subset', type=str, nargs=1)
+        parser.add_argument("-s", "--subset", type=str, nargs=1)
 
     def handle(self, *args, **options):
         # perform all checks
diff --git a/health_check/mixins.py b/health_check/mixins.py
index e32be97e..dd04180c 100644
--- a/health_check/mixins.py
+++ b/health_check/mixins.py
@@ -44,7 +44,7 @@ def filter_plugins(self, subset=None):
         if subset is None:
             return self.plugins
 
-        health_check_subsets = HEALTH_CHECK['SUBSETS']
+        health_check_subsets = HEALTH_CHECK["SUBSETS"]
         if subset not in health_check_subsets or not self.plugins:
             raise Http404(f"Specify subset: '{subset}' does not exists.")
 
diff --git a/tests/test_commands.py b/tests/test_commands.py
index 7c7aaf15..da2a7aec 100644
--- a/tests/test_commands.py
+++ b/tests/test_commands.py
@@ -38,30 +38,25 @@ def test_command(self):
         )
 
     def test_command_with_subset(self):
-        SUBSET_NAME_1 = 'subset-1'
-        SUBSET_NAME_2 = 'subset-2'
-        HEALTH_CHECK['SUBSETS'] = {
+        SUBSET_NAME_1 = "subset-1"
+        SUBSET_NAME_2 = "subset-2"
+        HEALTH_CHECK["SUBSETS"] = {
             SUBSET_NAME_1: ["OkPlugin"],
-            SUBSET_NAME_2: ["OkPlugin", "FailPlugin"]
+            SUBSET_NAME_2: ["OkPlugin", "FailPlugin"],
         }
 
         stdout = StringIO()
-        call_command(f"health_check", f"--subset={SUBSET_NAME_1}", stdout=stdout)
+        call_command("health_check", f"--subset={SUBSET_NAME_1}", stdout=stdout)
         stdout.seek(0)
-        assert stdout.read() == (
-            "OkPlugin                 ... working\n"
-        )
-
+        assert stdout.read() == ("OkPlugin                 ... working\n")
 
     def test_command_with_failed_check_subset(self):
-        SUBSET_NAME = 'subset-2'
-        HEALTH_CHECK['SUBSETS'] = {
-            SUBSET_NAME: ["OkPlugin", "FailPlugin"]
-        }
+        SUBSET_NAME = "subset-2"
+        HEALTH_CHECK["SUBSETS"] = {SUBSET_NAME: ["OkPlugin", "FailPlugin"]}
 
         stdout = StringIO()
         with pytest.raises(SystemExit):
-            call_command(f"health_check", f"--subset={SUBSET_NAME}", stdout=stdout)
+            call_command("health_check", f"--subset={SUBSET_NAME}", stdout=stdout)
         stdout.seek(0)
         assert stdout.read() == (
             "FailPlugin               ... unknown error: Oops\n"
@@ -69,15 +64,15 @@ def test_command_with_failed_check_subset(self):
         )
 
     def test_command_with_non_existence_subset(self):
-        SUBSET_NAME = 'subset-2'
+        SUBSET_NAME = "subset-2"
         NON_EXISTENCE_SUBSET_NAME = "abcdef12"
-        HEALTH_CHECK['SUBSETS'] = {
-            SUBSET_NAME: ["OkPlugin"]
-        }
+        HEALTH_CHECK["SUBSETS"] = {SUBSET_NAME: ["OkPlugin"]}
 
         stdout = StringIO()
         with pytest.raises(SystemExit):
-            call_command(f"health_check", f"--subset={NON_EXISTENCE_SUBSET_NAME}", stdout=stdout)
+            call_command(
+                "health_check", f"--subset={NON_EXISTENCE_SUBSET_NAME}", stdout=stdout
+            )
         stdout.seek(0)
         assert stdout.read() == (
             f"Specify subset: '{NON_EXISTENCE_SUBSET_NAME}' does not exists.\n"
diff --git a/tests/test_views.py b/tests/test_views.py
index 61047a29..d9161081 100644
--- a/tests/test_views.py
+++ b/tests/test_views.py
@@ -2,7 +2,6 @@
 
 import pytest
 
-from health_check import conf
 from health_check.backends import BaseHealthCheckBackend
 from health_check.conf import HEALTH_CHECK
 from health_check.exceptions import ServiceWarning
@@ -292,7 +291,7 @@ def run_check(self, subset=None):
         plugin_dir.register(SuccessOneBackend)
         plugin_dir.register(SuccessTwoBackend)
 
-        HEALTH_CHECK['SUBSETS'] = {
+        HEALTH_CHECK["SUBSETS"] = {
             "startup-probe": ["SuccessOneBackend", "SuccessTwoBackend"],
             "liveness-probe": ["SuccessTwoBackend"],
         }