diff --git a/tests/test_docker.py b/tests/test_docker.py
index 35c4244..c725979 100644
--- a/tests/test_docker.py
+++ b/tests/test_docker.py
@@ -69,11 +69,11 @@ class TestDockerValidation:
         with pytest.raises(ToolError, match="destructive"):
             await tool_fn(action="remove", container_id="abc123")
 
-    async def test_container_actions_require_id(self, _mock_graphql: AsyncMock) -> None:
+    @pytest.mark.parametrize("action", ["start", "stop", "details", "logs", "pause", "unpause"])
+    async def test_container_actions_require_id(self, _mock_graphql: AsyncMock, action: str) -> None:
         tool_fn = _make_tool()
-        for action in ("start", "stop", "details", "logs", "pause", "unpause"):
-            with pytest.raises(ToolError, match="container_id"):
-                await tool_fn(action=action)
+        with pytest.raises(ToolError, match="container_id"):
+            await tool_fn(action=action)
 
     async def test_network_details_requires_id(self, _mock_graphql: AsyncMock) -> None:
         tool_fn = _make_tool()
@@ -92,18 +92,19 @@ class TestDockerActions:
 
     async def test_start_container(self, _mock_graphql: AsyncMock) -> None:
         # First call resolves ID, second performs start
+        cid = "a" * 64 + ":local"
         _mock_graphql.side_effect = [
             {
                 "docker": {
                     "containers": [
-                        {"id": "abc123def456" * 4 + "abcd1234abcd1234:local", "names": ["plex"]}
+                        {"id": cid, "names": ["plex"]}
                     ]
                 }
             },
             {
                 "docker": {
                     "start": {
-                        "id": "abc123def456" * 4 + "abcd1234abcd1234:local",
+                        "id": cid,
                         "state": "running",
                     }
                 }
@@ -299,7 +300,7 @@ class TestDockerNetworkErrors:
         with pytest.raises(ToolError, match="Connection refused"):
             await tool_fn(action="list")
 
-    async def test_start_http_401_unauthorized(self, _mock_graphql: AsyncMock) -> None:
+    async def test_list_http_401_unauthorized(self, _mock_graphql: AsyncMock) -> None:
         """HTTP 401 should propagate as ToolError."""
         _mock_graphql.side_effect = ToolError("HTTP error 401: Unauthorized")
         tool_fn = _make_tool()
diff --git a/tests/test_storage.py b/tests/test_storage.py
index 6c9812f..9cd7867 100644
--- a/tests/test_storage.py
+++ b/tests/test_storage.py
@@ -109,6 +109,45 @@ class TestStorageActions:
         assert result["summary"]["temperature"] == "35\u00b0C"
         assert "1.00 GB" in result["summary"]["size_formatted"]
 
+    async def test_disk_details_temperature_zero(self, _mock_graphql: AsyncMock) -> None:
+        """Temperature of 0 should display as '0\u00b0C', not 'N/A'."""
+        _mock_graphql.return_value = {
+            "disk": {
+                "id": "d:1",
+                "device": "sda",
+                "name": "WD",
+                "serialNum": "SN1",
+                "size": 1073741824,
+                "temperature": 0,
+            }
+        }
+        tool_fn = _make_tool()
+        result = await tool_fn(action="disk_details", disk_id="d:1")
+        assert result["summary"]["temperature"] == "0\u00b0C"
+
+    async def test_disk_details_temperature_null(self, _mock_graphql: AsyncMock) -> None:
+        """Null temperature should display as 'N/A'."""
+        _mock_graphql.return_value = {
+            "disk": {
+                "id": "d:1",
+                "device": "sda",
+                "name": "WD",
+                "serialNum": "SN1",
+                "size": 1073741824,
+                "temperature": None,
+            }
+        }
+        tool_fn = _make_tool()
+        result = await tool_fn(action="disk_details", disk_id="d:1")
+        assert result["summary"]["temperature"] == "N/A"
+
+    async def test_logs_null_log_file(self, _mock_graphql: AsyncMock) -> None:
+        """logFile being null should return an empty dict."""
+        _mock_graphql.return_value = {"logFile": None}
+        tool_fn = _make_tool()
+        result = await tool_fn(action="logs", log_path="/var/log/syslog")
+        assert result == {}
+
     async def test_disk_details_not_found(self, _mock_graphql: AsyncMock) -> None:
         _mock_graphql.return_value = {"disk": None}
         tool_fn = _make_tool()
diff --git a/tests/test_vm.py b/tests/test_vm.py
index a18b2f3..7680a5d 100644
--- a/tests/test_vm.py
+++ b/tests/test_vm.py
@@ -158,10 +158,10 @@ class TestVmMutationFailures:
         assert result["action"] == "start"
 
     async def test_stop_mutation_returns_null(self, _mock_graphql: AsyncMock) -> None:
-        """VM stop returning None in the field should raise ToolError (field not 'in' data)."""
+        """VM stop returning None in the field should succeed (key exists, value is None)."""
         _mock_graphql.return_value = {"vm": {"stop": None}}
         tool_fn = _make_tool()
-        # The check is `field in data["vm"]` — None is truthy for `in`, so it succeeds
+        # The check is `field in data["vm"]` — `in` checks key existence, not truthiness
         result = await tool_fn(action="stop", vm_id="uuid-1")
         assert result["success"] is None
         assert result["action"] == "stop"