diff --git a/goodwe_controller/test_setup.py b/goodwe_controller/test_setup.py
index ebcd97c..4de85cf 100644
--- a/goodwe_controller/test_setup.py
+++ b/goodwe_controller/test_setup.py
@@ -28,7 +28,7 @@ HERE = os.path.dirname(os.path.abspath(__file__))
 sys.path.insert(0, os.path.join(HERE, "tools"))
 logging.disable(logging.WARNING)            # the validator's own log lines
 
-from aiohttp import ClientSession, web as aioweb                # noqa: E402
+from aiohttp import ClientSession, ContentTypeError, web as aioweb  # noqa: E402
 
 import translations_lint as TL                                  # noqa: E402
 import ux13_demo as D                                           # noqa: E402
@@ -264,7 +264,10 @@ async def _get(s, url):
 
 async def _post(s, url, body):
     async with s.post(url, json=body) as r:
-        return r.status, await r.json()
+        try:
+            return r.status, await r.json()
+        except (ValueError, ContentTypeError):    # e.g. a plain-text 500
+            return r.status, {}
 
 
 STATES = [state("sensor.grid", "402"), state("number.inv1_power", "0"),
@@ -790,18 +793,18 @@ async def _f1(s, root, sup):
 
 _r, _sup = asyncio.run(session(Controller(SITE, STATES, Store(), grid=402.0),
                                SITE, _f1))
-print(f"    empty day price: steps {_r['price']['steps']}")
+print(f"    empty day price: steps {_r['price'].get('steps')}")
 check("F1: a price the page cannot turn into options blocks step 4, beside "
       "its own field",
-      _r["price"]["steps"]["4"] >= 1
+      _r["price"].get("steps", {}).get("4", 0) >= 1
       and {"field": "ui.day_price", "card": None, "tier": "bad",
-           "text": WS_D["no_price"]["description"]} in _r["price"]["messages"])
+           "text": WS_D["no_price"]["description"]} in _r["price"].get("messages", []))
 check("F1: ...and the last step's live checks still run on the rest",
       [x["tier"] for x in _r["price"].get("setup", [])
        if "number.inv1_power" in x["text"]] == ["ok"]
       and any("402 W" in x["text"] for x in _r["price"]["setup"]))
 check("F1: no inverter card blocks step 2, not the last step alone",
-      _r["none"]["steps"]["2"] >= 1)
+      _r["none"].get("steps", {}).get("2", 0) >= 1)
 check("F1: the save refuses it (422) and says which step to go back to",
       _r["save"][0] == 422 and _r["save"][1]["steps"]["4"] >= 1
       and _sup.writes == [])
diff --git a/goodwe_controller/test_setup_only.py b/goodwe_controller/test_setup_only.py
index e880155..3da2d5e 100644
--- a/goodwe_controller/test_setup_only.py
+++ b/goodwe_controller/test_setup_only.py
@@ -339,10 +339,14 @@ class Session:
 
 
 def _refused(coro):
+    """True only for the read-only refusal; a request that reached the
+    session (AssertionError there) or no refusal at all is False."""
     try:
         asyncio.run(coro)
     except H.ReadOnly:
         return True
+    except Exception:                                   # noqa: BLE001
+        return False
     return False
 
 
@@ -372,8 +376,10 @@ check("control: a normal HomeAssistant does send the write", _sent
 try:
     M.Controller(dict(_ok), _ro, None, None, stop=asyncio.Event())
     _built = True
-except ValueError:
-    _built = False
+except ValueError as err:
+    _built = "read-only" not in str(err)
+except Exception:                                       # noqa: BLE001
+    _built = True           # it got past the check and failed on something else
 check("no controller can be built on a read-only HomeAssistant", not _built)
 try:
     setuponly.SetupOnly(SHIPPED, _rw, None)