test: cover electron boundary modules

tests/unit/update-installer.test.ts

@@ -0,0 +1,33 @@
+import path from 'path'
+import { describe, expect, it } from 'vitest'
+import { UpdateInstaller } from '../../src/main/services/update/update-installer'
+
+describe('UpdateInstaller', () => {
+  it('builds downloaded package path under userData pending-update', () => {
+    const installer = new UpdateInstaller()
+
+    const result = installer.getDownloadPath({
+      version: '1.2.3',
+      channel: 'stable'
+    })
+
+    expect(result).toContain(path.join('logs', 'pending-update'))
+    expect(result).toContain('stable-1.2.3.exe')
+  })
+
+  it('returns null when downloaded package does not exist', async () => {
+    const installer = new UpdateInstaller()
+
+    const result = await installer.getValidDownloadedRelease({
+      version: '9.9.9',
+      channel: 'preview',
+      artifactKey: 'preview/9.9.9.exe',
+      sha256: 'missing',
+      size: 1,
+      publishedAt: '2026-03-21T10:00:00Z',
+      changelogKey: 'preview/9.9.9.md'
+    })
+
+    expect(result).toBeNull()
+  })
+})