diff --git a/test/database.test.tsx b/test/database.test.tsx
new file mode 100644
index 0000000..23b2dea
--- /dev/null
+++ b/test/database.test.tsx
@@ -0,0 +1,237 @@
+import { describe, it, vi, beforeEach, afterEach, expect } from 'vitest'
+import NoteController from '@/lib/controller/NoteController'
+import EdgeController from '@/lib/controller/EdgeController'
+import ChatHistoryController from '@/lib/controller/ChatHistoryController'
+import KeyController from '@/lib/controller/KeyController'
+import Database from '@/lib/Database'
+
+describe('Edge operations', () => {
+  let edgeController: EdgeController
+
+  beforeEach(async () => {
+    vi.clearAllMocks()
+
+    const sqliteMock = await import('@tauri-apps/plugin-sql')
+    const driverMock = {
+      execute: vi.fn().mockResolvedValue({ rowsAffected: 1 }),
+      select: vi.fn().mockResolvedValue([])
+    }
+    sqliteMock.default.load = vi.fn().mockResolvedValue(driverMock)
+    edgeController = new EdgeController(':memory:')
+  })
+
+  afterEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('should use SQL constraint to prevent duplicate edges', async () => {
+    const executeSpy = vi.spyOn(edgeController as any, 'execute')
+    await edgeController.create({ src: 1, dst: 2 })
+    expect(executeSpy).toHaveBeenCalledWith(
+      expect.stringContaining('ON CONFLICT(src, dst) DO NOTHING'),
+      [1, 2]
+    )
+  })
+})
+
+describe('Chat History operations', () => {
+  let chatHistoryController: ChatHistoryController
+
+  beforeEach(async () => {
+    vi.clearAllMocks()
+    const sqliteMock = await import('@tauri-apps/plugin-sql')
+    const driverMock = {
+      execute: vi.fn().mockResolvedValue({ rowsAffected: 1 }),
+      select: vi.fn().mockResolvedValue([])
+    }
+    sqliteMock.default.load = vi.fn().mockResolvedValue(driverMock)
+    chatHistoryController = new ChatHistoryController(':memory:')
+  })
+
+  afterEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('should query chat history in ascending order of timestamp', async () => {
+    const selectSpy = vi.spyOn(chatHistoryController as any, 'select')
+    await chatHistoryController.readAll()
+    expect(selectSpy).toHaveBeenCalledWith(
+      expect.stringContaining(`ORDER BY time;`))
+  })
+})
+
+describe('Database operations', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  afterEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('should create database tables on startup', async () => {
+    const database = new Database(':memory:')
+
+    const sqliteMock = await import('@tauri-apps/plugin-sql')
+    const driverMock = {
+      execute: vi.fn().mockResolvedValue({ rowsAffected: 1 }),
+      select: vi.fn().mockResolvedValue([])
+    }
+    sqliteMock.default.load = vi.fn().mockResolvedValue(driverMock)
+
+    await database.connect()
+
+    expect(driverMock.execute).toHaveBeenCalledWith(expect.stringContaining('CREATE TABLE IF NOT EXISTS Notes'))
+    expect(driverMock.execute).toHaveBeenCalledWith(expect.stringContaining('CREATE TABLE IF NOT EXISTS Edges'))
+    expect(driverMock.execute).toHaveBeenCalledWith(expect.stringContaining('CREATE TABLE IF NOT EXISTS Keys'))
+    expect(driverMock.execute).toHaveBeenCalledWith(expect.stringContaining('CREATE TABLE IF NOT EXISTS Chat_History'))
+    expect(driverMock.execute).toHaveBeenCalledWith(expect.stringContaining('CREATE VIRTUAL TABLE IF NOT EXISTS Search'))
+  })
+
+  it('should throw error if database is not connected before executing queries', async () => {
+    const database = new Database(':memory:')
+    await expect(database.execute('SELECT * FROM Notes')).rejects.toThrow('database is disconnected')
+    await expect(database.select('SELECT * FROM Notes')).rejects.toThrow('database is disconnected')
+  })
+})
+
+describe('Note operations', () => {
+  let noteController: NoteController
+
+  beforeEach(() => {
+    noteController = new NoteController(':memory:')
+    vi.clearAllMocks()
+  })
+
+  afterEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('should query search with proper SQL for content searching', async () => {
+    const selectSpy = vi.spyOn(noteController as any, 'select')
+    const searchTerm = 'search term'
+    await noteController.search(searchTerm)
+
+    expect(selectSpy).toHaveBeenCalledWith(
+      expect.stringContaining('FROM Search'),
+      expect.arrayContaining([expect.stringContaining('search term')])
+    )
+
+    expect(selectSpy).toHaveBeenCalledWith(
+      expect.stringContaining('Search.content MATCH ?'),
+      expect.any(Array)
+    )
+  })
+})
+
+describe('Controller connection behavior', () => {
+  let noteController: NoteController
+  let edgeController: EdgeController
+  let chatHistoryController: ChatHistoryController
+  let keyController: KeyController
+
+  beforeEach(async () => {
+    vi.clearAllMocks()
+
+    const sqliteMock = await import('@tauri-apps/plugin-sql')
+    const driverMock = {
+      execute: vi.fn().mockResolvedValue({ rowsAffected: 1 }),
+      select: vi.fn().mockResolvedValue([])
+    }
+    sqliteMock.default.load = vi.fn().mockResolvedValue(driverMock)
+
+    noteController = new NoteController(':memory:')
+    edgeController = new EdgeController(':memory:')
+    chatHistoryController = new ChatHistoryController(':memory:')
+    keyController = new KeyController(':memory:')
+  })
+
+  afterEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('NoteController should establish connection before executing queries', async () => {
+    const ensureConnectedSpy = vi.spyOn(noteController as any, 'ensureConnected')
+    const connectSpy = vi.spyOn(noteController as any, 'connect')
+
+    // Force controller to think it's not connected
+    Object.defineProperty(noteController, 'ready', { value: false, writable: true })
+
+    await noteController.readAll()
+
+    expect(ensureConnectedSpy).toHaveBeenCalledTimes(1)
+    expect(connectSpy).toHaveBeenCalledTimes(1)
+
+    // Set ready to true as it would be after first connection
+    Object.defineProperty(noteController, 'ready', { value: true, writable: true })
+    ensureConnectedSpy.mockClear()
+    connectSpy.mockClear()
+
+    await noteController.readAll()
+
+    expect(ensureConnectedSpy).toHaveBeenCalledTimes(1)
+    expect(connectSpy).not.toHaveBeenCalled()
+  })
+
+  it('EdgeController should establish connection before executing queries', async () => {
+    const ensureConnectedSpy = vi.spyOn(edgeController as any, 'ensureConnected')
+    const connectSpy = vi.spyOn(edgeController as any, 'connect')
+
+    Object.defineProperty(edgeController, 'ready', { value: false, writable: true })
+    await edgeController.readAll()
+
+    expect(ensureConnectedSpy).toHaveBeenCalledTimes(1)
+    expect(connectSpy).toHaveBeenCalledTimes(1)
+
+    Object.defineProperty(edgeController, 'ready', { value: true, writable: true })
+    ensureConnectedSpy.mockClear()
+    connectSpy.mockClear()
+
+    await edgeController.readAll()
+
+    expect(ensureConnectedSpy).toHaveBeenCalledTimes(1)
+    expect(connectSpy).not.toHaveBeenCalled()
+  })
+
+  it('ChatHistoryController should establish connection before executing queries', async () => {
+    const ensureConnectedSpy = vi.spyOn(chatHistoryController as any, 'ensureConnected')
+    const connectSpy = vi.spyOn(chatHistoryController as any, 'connect')
+
+    Object.defineProperty(chatHistoryController, 'ready', { value: false, writable: true })
+
+    await chatHistoryController.readAll()
+
+    expect(ensureConnectedSpy).toHaveBeenCalledTimes(1)
+    expect(connectSpy).toHaveBeenCalledTimes(1)
+
+    Object.defineProperty(chatHistoryController, 'ready', { value: true, writable: true })
+    ensureConnectedSpy.mockClear()
+    connectSpy.mockClear()
+
+    await chatHistoryController.readAll()
+
+    expect(ensureConnectedSpy).toHaveBeenCalledTimes(1)
+    expect(connectSpy).not.toHaveBeenCalled()
+  })
+
+  it('KeyController should establish connection before executing queries', async () => {
+    const ensureConnectedSpy = vi.spyOn(keyController as any, 'ensureConnected')
+    const connectSpy = vi.spyOn(keyController as any, 'connect')
+
+    Object.defineProperty(keyController, 'ready', { value: false, writable: true })
+
+    await keyController.readAll()
+
+    expect(ensureConnectedSpy).toHaveBeenCalledTimes(1)
+    expect(connectSpy).toHaveBeenCalledTimes(1)
+
+    Object.defineProperty(keyController, 'ready', { value: true, writable: true })
+    ensureConnectedSpy.mockClear()
+    connectSpy.mockClear()
+
+    await keyController.readAll()
+
+    expect(ensureConnectedSpy).toHaveBeenCalledTimes(1)
+    expect(connectSpy).not.toHaveBeenCalled()
+  })
+})
diff --git a/vitest.config.ts b/vitest.config.ts
index 74e4982..310156a 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -1,6 +1,7 @@
 /// <reference types="vitest" />
 import { defineConfig } from 'vitest/config'
 import react from '@vitejs/plugin-react'
+import path from 'path'
 
 export default defineConfig({
   plugins: [react()],
@@ -9,4 +10,9 @@ export default defineConfig({
     environment: 'jsdom',
     setupFiles: './test/setup.ts',
   },
-})
+  resolve: {
+    alias: {
+      '@': path.resolve(__dirname, './'),
+    },
+  },
+})
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