test(macos): cover installer platform guards

tests/test_macos_install.py

@@ -0,0 +1,33 @@
+"""Platform guards for the community-supported native macOS install path."""
+from __future__ import annotations
+
+import importlib.util
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+SPEC = importlib.util.spec_from_file_location("nexus_sync_macos_test", ROOT / "bin" / "sync.py")
+assert SPEC and SPEC.loader
+sync = importlib.util.module_from_spec(SPEC)
+SPEC.loader.exec_module(sync)
+
+
+def test_darwin_uses_gpu_agnostic_requirements(monkeypatch):
+    monkeypatch.setattr(sync.os, "name", "posix")
+    monkeypatch.setattr(sync.sys, "platform", "darwin")
+    assert sync.requirements() == "requirements-base.txt"
+
+
+def test_linux_provisioning_stages_are_skipped_on_darwin(monkeypatch):
+    monkeypatch.setattr(sync.sys, "platform", "darwin")
+
+    def unexpected_run(*args, **kwargs):
+        raise AssertionError(f"Linux provisioning ran on macOS: {args!r}")
+
+    monkeypatch.setattr(sync.subprocess, "run", unexpected_run)
+    sync.linux_stage("restore-linux.sh", "packages")
+
+
+def test_macos_installer_is_in_the_shell_parse_gate():
+    gate = (ROOT / "bin" / "check.sh").read_text(encoding="utf-8")
+    assert "install-macos.sh" in gate