Test local RAM probe fallbacks

Cover broken psutil, Linux procfs fallback, macOS/POSIX sysconf fallback, and fail-closed behavior when every probe is unavailable.

tests/test_local_ui_portability.py

@@ -2,7 +2,9 @@
 
 from __future__ import annotations
 
-from unittest.mock import Mock
+import sys
+from types import SimpleNamespace
+from unittest.mock import Mock, mock_open
 
 from obliteratus import local_ui
 
@@ -33,3 +35,38 @@ def test_system_info_queries_the_platform_temp_directory(monkeypatch, tmp_path):
     local_ui._print_system_info([])
 
     disk_free.assert_called_once_with(str(tmp_path))
+
+
+def test_ram_detection_falls_back_from_broken_psutil_to_proc(monkeypatch):
+    broken_psutil = SimpleNamespace(
+        virtual_memory=Mock(side_effect=OSError("unavailable")),
+    )
+    monkeypatch.setitem(sys.modules, "psutil", broken_psutil)
+    monkeypatch.setattr(
+        "builtins.open",
+        mock_open(read_data="MemTotal:       2097152 kB\n"),
+    )
+
+    assert local_ui._get_ram_gb() == 2.0
+
+
+def test_ram_detection_uses_posix_sysconf_without_psutil_or_proc(monkeypatch):
+    monkeypatch.setitem(sys.modules, "psutil", None)
+    monkeypatch.setattr("builtins.open", Mock(side_effect=OSError("no procfs")))
+    values = {"SC_PHYS_PAGES": 1_048_576, "SC_PAGE_SIZE": 4096}
+    sysconf = Mock(side_effect=values.__getitem__)
+    monkeypatch.setattr(local_ui.os, "sysconf", sysconf)
+
+    assert local_ui._get_ram_gb() == 4.0
+    assert [call.args[0] for call in sysconf.call_args_list] == [
+        "SC_PHYS_PAGES",
+        "SC_PAGE_SIZE",
+    ]
+
+
+def test_ram_detection_fails_closed_when_all_probes_are_unavailable(monkeypatch):
+    monkeypatch.setitem(sys.modules, "psutil", None)
+    monkeypatch.setattr("builtins.open", Mock(side_effect=OSError("no procfs")))
+    monkeypatch.setattr(local_ui.os, "sysconf", Mock(side_effect=OSError("unsupported")))
+
+    assert local_ui._get_ram_gb() == 0.0