add missing unit test suite

tests/nav-preferences.test.ts

@@ -0,0 +1,37 @@
+/**
+ * Unit tests for nav-preferences.ts — the PURE validation (parseNavPatch). It has no DB
+ * dependency, so it imports directly with no mock.module (mocking ./db here is unsafe: bun's
+ * mock.module is process-global and would clobber the ./db export set other backup unit tests
+ * rely on, e.g. route-guards.test.ts's getBackupConfig). The merge/defaults + env-deletion
+ * sweep touch the DB and are exercised via the integration suite, not mocked here.
+ */
+import { describe, it, expect } from 'bun:test';
+import { parseNavPatch, PAGE_SLUGS } from '../src/lib/server/nav-preferences-core';
+
+describe('parseNavPatch — validation', () => {
+	it('accepts every real page slug for landingPage', () => {
+		for (const p of PAGE_SLUGS) {
+			expect(parseNavPatch({ landingPage: p })).toEqual({ landingPage: p });
+		}
+	});
+	it("rejects 'remember' for landingPage (feature removed)", () => {
+		expect(() => parseNavPatch({ landingPage: 'remember' })).toThrow('Invalid landingPage');
+	});
+	it("treats '' and null as a clear (null)", () => {
+		expect(parseNavPatch({ landingPage: '' })).toEqual({ landingPage: null });
+		expect(parseNavPatch({ landingPage: null })).toEqual({ landingPage: null });
+	});
+	it('rejects an unknown landingPage', () => {
+		expect(() => parseNavPatch({ landingPage: 'nope' })).toThrow('Invalid landingPage');
+	});
+	it("rejects 'dashboard' for envClickPage (concrete per-env only)", () => {
+		expect(() => parseNavPatch({ envClickPage: 'dashboard' })).toThrow('Invalid envClickPage');
+	});
+	it('accepts an env-scoped page for envClickPage', () => {
+		expect(parseNavPatch({ envClickPage: 'stacks' })).toEqual({ envClickPage: 'stacks' });
+	});
+	it('ignores fields that are not present (partial patch)', () => {
+		expect(parseNavPatch({})).toEqual({});
+		expect(parseNavPatch({ landingPage: 'logs' })).toEqual({ landingPage: 'logs' });
+	});
+});