diff --git a/caprover/gc-stack-deploy/src/gc_stack_deploy/apps_registry.py b/caprover/gc-stack-deploy/src/gc_stack_deploy/apps_registry.py
index 636d62b..2ed4522 100644
--- a/caprover/gc-stack-deploy/src/gc_stack_deploy/apps_registry.py
+++ b/caprover/gc-stack-deploy/src/gc_stack_deploy/apps_registry.py
@@ -49,6 +49,21 @@ def set_yaml_value(yaml_str: str | None, key: str | list[str], value: object) ->
     return buf.getvalue()
 
 
+def disable_healthcheck(suo: str | None) -> str:
+    """
+    Return a serviceUpdateOverride YAML with the Docker healthcheck disabled.
+
+    HealthCheck gets nested under TaskTemplate.ContainerSpec; I can't find
+    documentation for that, you will have to trust me (from trial-and-error).
+
+    TaskTemplate:
+      ContainerSpec:
+        HealthCheck:
+          Test: ["NONE"]
+    """
+    return set_yaml_value(suo, "TaskTemplate.ContainerSpec.HealthCheck.Test", ["NONE"])
+
+
 def set_memory_limit(cap, appname, memory_bytes=1610612736):
     app = cap.get_app(appname)
     new_suo = set_yaml_value(
@@ -311,11 +326,7 @@ def _install(self) -> None:
                 f"{self.app_name}-worker",
             ):
                 worker_app = cap.get_app(appname)
-                new_suo = set_yaml_value(
-                    worker_app["serviceUpdateOverride"],
-                    "TaskTemplate.HealthCheck.Test",
-                    ["NONE"],
-                )
+                new_suo = disable_healthcheck(worker_app["serviceUpdateOverride"])
                 # Also set memory limit to workers
                 new_suo = set_yaml_value(
                     new_suo, "TaskTemplate.Resources.Limits.MemoryBytes", 1610612736
diff --git a/caprover/gc-stack-deploy/tests/apps_registry_test.py b/caprover/gc-stack-deploy/tests/apps_registry_test.py
new file mode 100644
index 0000000..45b6d72
--- /dev/null
+++ b/caprover/gc-stack-deploy/tests/apps_registry_test.py
@@ -0,0 +1,77 @@
+import pytest
+from ruamel.yaml import YAML
+
+from gc_stack_deploy.apps_registry import disable_healthcheck, set_yaml_value
+
+
+def load_yaml(s):
+    return YAML().load(s)
+
+
+class TestSetYamlValue:
+    def test_creates_nested_keys_from_scratch(self):
+        result = set_yaml_value(None, "A.B.C", 42)
+        assert load_yaml(result) == {"A": {"B": {"C": 42}}}
+
+    def test_sets_value_in_existing_document(self):
+        existing = (
+            "A:\n"
+            "  B:\n"
+            "    C: 1\n"
+        )
+        result = set_yaml_value(existing, "A.B.C", 99)
+        assert load_yaml(result)["A"]["B"]["C"] == 99
+
+    def test_preserves_sibling_keys(self):
+        existing = (
+            "A:\n"
+            "  X: kept\n"
+            "  B:\n"
+            "    C: 1\n"
+        )
+        result = set_yaml_value(existing, "A.B.C", 2)
+        data = load_yaml(result)
+        assert data["A"]["X"] == "kept"
+        assert data["A"]["B"]["C"] == 2
+
+    def test_accepts_list_key(self):
+        result = set_yaml_value(None, ["A", "B"], "v")
+        assert load_yaml(result) == {"A": {"B": "v"}}
+
+    def test_empty_string_treated_as_empty(self):
+        result = set_yaml_value("", "K", "v")
+        assert load_yaml(result) == {"K": "v"}
+
+    def test_list_value(self):
+        result = set_yaml_value(None, "A.B", ["NONE"])
+        assert load_yaml(result) == {"A": {"B": ["NONE"]}}
+
+
+class TestDisableHealthcheck:
+    HEALTHCHECK_ONLY = (
+        "TaskTemplate:\n"
+        "  ContainerSpec:\n"
+        "    HealthCheck:\n"
+        "      Test:\n"
+        "      - NONE\n"
+    )
+
+    def test_none_input(self):
+        assert disable_healthcheck(None) == self.HEALTHCHECK_ONLY
+
+    def test_empty_string_input(self):
+        assert disable_healthcheck("") == self.HEALTHCHECK_ONLY
+
+    def test_disables_on_existing_suo(self):
+        existing = "TaskTemplate:\n  Resources:\n    Limits:\n      MemoryBytes: 1024\n"
+        expected = (
+            "TaskTemplate:\n"
+            "  Resources:\n"
+            "    Limits:\n"
+            "      MemoryBytes: 1024\n"
+            "  ContainerSpec:\n"
+            "    HealthCheck:\n"
+            "      Test:\n"
+            "      - NONE\n"
+        )
+        assert disable_healthcheck(existing) == expected