diff --git a/frontends/nextjs/src/seed-data/index.test.ts b/frontends/nextjs/src/seed-data/index.test.ts
new file mode 100644
index 000000000..011079604
--- /dev/null
+++ b/frontends/nextjs/src/seed-data/index.test.ts
@@ -0,0 +1,71 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest'
+
+const {
+  initializeUsers,
+  initializeComponents,
+  initializeScripts,
+  initializeWorkflows,
+  initializePages,
+  initializePackages,
+} = vi.hoisted(() => ({
+  initializeUsers: vi.fn(),
+  initializeComponents: vi.fn(),
+  initializeScripts: vi.fn(),
+  initializeWorkflows: vi.fn(),
+  initializePages: vi.fn(),
+  initializePackages: vi.fn(),
+}))
+
+vi.mock('./users', () => ({ initializeUsers }))
+vi.mock('./components', () => ({ initializeComponents }))
+vi.mock('./scripts', () => ({ initializeScripts }))
+vi.mock('./workflows', () => ({ initializeWorkflows }))
+vi.mock('./pages', () => ({ initializePages }))
+vi.mock('./packages', () => ({ initializePackages }))
+
+import { initializeAllSeedData } from './index'
+
+describe('initializeAllSeedData', () => {
+  beforeEach(() => {
+    initializeUsers.mockReset()
+    initializeComponents.mockReset()
+    initializeScripts.mockReset()
+    initializeWorkflows.mockReset()
+    initializePages.mockReset()
+    initializePackages.mockReset()
+  })
+
+  it.each([
+    {
+      name: 'run seeders in order',
+      errorStep: null as string | null,
+      expectedCalls: ['users', 'components', 'scripts', 'workflows', 'pages', 'packages'],
+    },
+    {
+      name: 'stop when a seeder fails',
+      errorStep: 'scripts',
+      expectedCalls: ['users', 'components', 'scripts'],
+    },
+  ])('should $name', async ({ errorStep, expectedCalls }) => {
+    const callOrder: string[] = []
+    initializeUsers.mockImplementation(async () => callOrder.push('users'))
+    initializeComponents.mockImplementation(async () => callOrder.push('components'))
+    initializeScripts.mockImplementation(async () => {
+      callOrder.push('scripts')
+      if (errorStep === 'scripts') {
+        throw new Error('seed failed')
+      }
+    })
+    initializeWorkflows.mockImplementation(async () => callOrder.push('workflows'))
+    initializePages.mockImplementation(async () => callOrder.push('pages'))
+    initializePackages.mockImplementation(async () => callOrder.push('packages'))
+
+    if (errorStep) {
+      await expect(initializeAllSeedData()).rejects.toThrow('seed failed')
+    } else {
+      await expect(initializeAllSeedData()).resolves.toBeUndefined()
+    }
+
+    expect(callOrder).toEqual(expectedCalls)
+  })
+})
diff --git a/frontends/nextjs/src/seed-data/packages.test.ts b/frontends/nextjs/src/seed-data/packages.test.ts
new file mode 100644
index 000000000..b2c152cac
--- /dev/null
+++ b/frontends/nextjs/src/seed-data/packages.test.ts
@@ -0,0 +1,32 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest'
+
+const { initializePackageSystem } = vi.hoisted(() => ({
+  initializePackageSystem: vi.fn(),
+}))
+
+vi.mock('@/lib/package-loader', () => ({
+  initializePackageSystem,
+}))
+
+import { initializePackages } from '@/seed-data/packages'
+
+describe('initializePackages', () => {
+  beforeEach(() => {
+    initializePackageSystem.mockReset()
+  })
+
+  it.each([
+    { name: 'resolve when initializer succeeds', error: null as Error | null },
+    { name: 'propagate errors from initializer', error: new Error('init failed') },
+  ])('should $name', async ({ error }) => {
+    if (error) {
+      initializePackageSystem.mockRejectedValueOnce(error)
+      await expect(initializePackages()).rejects.toThrow('init failed')
+    } else {
+      initializePackageSystem.mockResolvedValueOnce(undefined)
+      await expect(initializePackages()).resolves.toBeUndefined()
+    }
+
+    expect(initializePackageSystem).toHaveBeenCalledTimes(1)
+  })
+})
diff --git a/frontends/nextjs/src/seed-data/pages.test.ts b/frontends/nextjs/src/seed-data/pages.test.ts
new file mode 100644
index 000000000..d822bb23c
--- /dev/null
+++ b/frontends/nextjs/src/seed-data/pages.test.ts
@@ -0,0 +1,60 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest'
+
+const { getPages } = vi.hoisted(() => ({
+  getPages: vi.fn(),
+}))
+
+const { initializeDefaultPages } = vi.hoisted(() => ({
+  initializeDefaultPages: vi.fn(),
+}))
+
+const { getPageDefinitionBuilder } = vi.hoisted(() => ({
+  getPageDefinitionBuilder: vi.fn(),
+}))
+
+vi.mock('@/lib/database', () => ({
+  Database: {
+    getPages,
+  },
+}))
+
+vi.mock('@/lib/page-definition-builder', () => ({
+  getPageDefinitionBuilder,
+}))
+
+import { initializePages } from '@/seed-data/pages'
+
+describe('initializePages', () => {
+  beforeEach(() => {
+    getPages.mockReset()
+    getPageDefinitionBuilder.mockReset()
+    initializeDefaultPages.mockReset()
+  })
+
+  it.each([
+    {
+      name: 'skip initialization when pages exist',
+      existingPages: [{ id: 'page1' }],
+      shouldInitialize: false,
+    },
+    {
+      name: 'initialize defaults when no pages exist',
+      existingPages: [],
+      shouldInitialize: true,
+    },
+  ])('should $name', async ({ existingPages, shouldInitialize }) => {
+    getPages.mockResolvedValue(existingPages)
+    getPageDefinitionBuilder.mockReturnValue({ initializeDefaultPages })
+
+    await initializePages()
+
+    expect(getPages).toHaveBeenCalledTimes(1)
+    if (shouldInitialize) {
+      expect(getPageDefinitionBuilder).toHaveBeenCalledTimes(1)
+      expect(initializeDefaultPages).toHaveBeenCalledTimes(1)
+    } else {
+      expect(getPageDefinitionBuilder).not.toHaveBeenCalled()
+      expect(initializeDefaultPages).not.toHaveBeenCalled()
+    }
+  })
+})
diff --git a/frontends/nextjs/src/seed-data/scripts.test.ts b/frontends/nextjs/src/seed-data/scripts.test.ts
new file mode 100644
index 000000000..1aefa57e6
--- /dev/null
+++ b/frontends/nextjs/src/seed-data/scripts.test.ts
@@ -0,0 +1,56 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest'
+
+const { getLuaScripts, addLuaScript } = vi.hoisted(() => ({
+  getLuaScripts: vi.fn(),
+  addLuaScript: vi.fn(),
+}))
+
+vi.mock('@/lib/database', () => ({
+  Database: {
+    getLuaScripts,
+    addLuaScript,
+  },
+}))
+
+import { initializeScripts } from '@/seed-data/scripts'
+
+const expectedScriptIds = [
+  'script_welcome_message',
+  'script_format_date',
+  'script_validate_email',
+  'script_permission_check',
+  'script_page_load_analytics',
+]
+
+describe('initializeScripts', () => {
+  beforeEach(() => {
+    getLuaScripts.mockReset()
+    addLuaScript.mockReset()
+  })
+
+  it.each([
+    {
+      name: 'skip seeding when scripts exist',
+      existingScripts: [{ id: 'existing' }],
+      expectedAdds: 0,
+    },
+    {
+      name: 'seed default scripts when none exist',
+      existingScripts: [],
+      expectedAdds: expectedScriptIds.length,
+    },
+  ])('should $name', async ({ existingScripts, expectedAdds }) => {
+    getLuaScripts.mockResolvedValue(existingScripts)
+
+    await initializeScripts()
+
+    expect(getLuaScripts).toHaveBeenCalledTimes(1)
+    expect(addLuaScript).toHaveBeenCalledTimes(expectedAdds)
+
+    if (expectedAdds > 0) {
+      expectedScriptIds.forEach(id => {
+        expect(addLuaScript).toHaveBeenCalledWith(expect.objectContaining({ id }))
+      })
+    }
+  })
+})
diff --git a/frontends/nextjs/src/seed-data/users.test.ts b/frontends/nextjs/src/seed-data/users.test.ts
new file mode 100644
index 000000000..253d6365e
--- /dev/null
+++ b/frontends/nextjs/src/seed-data/users.test.ts
@@ -0,0 +1,98 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest'
+
+const {
+  getUsers,
+  setCredential,
+  setFirstLoginFlag,
+  addUser,
+  setGodCredentialsExpiry,
+  hashPassword,
+} = vi.hoisted(() => ({
+  getUsers: vi.fn(),
+  setCredential: vi.fn(),
+  setFirstLoginFlag: vi.fn(),
+  addUser: vi.fn(),
+  setGodCredentialsExpiry: vi.fn(),
+  hashPassword: vi.fn(),
+}))
+
+const { getScrambledPassword } = vi.hoisted(() => ({
+  getScrambledPassword: vi.fn(),
+}))
+
+vi.mock('@/lib/database', () => ({
+  Database: {
+    getUsers,
+    setCredential,
+    setFirstLoginFlag,
+    addUser,
+    setGodCredentialsExpiry,
+  },
+  hashPassword,
+}))
+
+vi.mock('@/lib/auth', () => ({
+  getScrambledPassword,
+}))
+
+import { initializeUsers } from '@/seed-data/users'
+
+const expectedUsernames = ['supergod', 'god', 'admin', 'alice', 'bob']
+
+describe('initializeUsers', () => {
+  beforeEach(() => {
+    getUsers.mockReset()
+    setCredential.mockReset()
+    setFirstLoginFlag.mockReset()
+    addUser.mockReset()
+    setGodCredentialsExpiry.mockReset()
+    hashPassword.mockReset()
+    getScrambledPassword.mockReset()
+  })
+
+  it.each([
+    {
+      name: 'skip seeding when users exist',
+      existingUsers: [{ id: 'existing' }],
+      expectedAdds: 0,
+    },
+    {
+      name: 'seed users when none exist',
+      existingUsers: [],
+      expectedAdds: expectedUsernames.length,
+    },
+  ])('should $name', async ({ existingUsers, expectedAdds }) => {
+    const nowSpy = vi.spyOn(Date, 'now').mockReturnValue(1000)
+    getUsers.mockResolvedValue(existingUsers)
+    getScrambledPassword.mockImplementation((username: string) => `scrambled-${username}`)
+    hashPassword.mockImplementation(async (value: string) => `hash-${value}`)
+
+    if (expectedAdds === 0) {
+      await initializeUsers()
+    } else {
+      await expect(initializeUsers()).resolves.toBeUndefined()
+    }
+
+    expect(getUsers).toHaveBeenCalledTimes(1)
+    expect(addUser).toHaveBeenCalledTimes(expectedAdds)
+    expect(setCredential).toHaveBeenCalledTimes(expectedAdds)
+    expect(setFirstLoginFlag).toHaveBeenCalledTimes(expectedAdds)
+
+    if (expectedAdds === 0) {
+      expect(getScrambledPassword).not.toHaveBeenCalled()
+      expect(hashPassword).not.toHaveBeenCalled()
+      expect(setGodCredentialsExpiry).not.toHaveBeenCalled()
+    } else {
+      expectedUsernames.forEach(username => {
+        expect(getScrambledPassword).toHaveBeenCalledWith(username)
+        expect(hashPassword).toHaveBeenCalledWith(`scrambled-${username}`)
+        expect(setCredential).toHaveBeenCalledWith(username, `hash-scrambled-${username}`)
+        expect(setFirstLoginFlag).toHaveBeenCalledWith(username, true)
+        expect(addUser).toHaveBeenCalledWith(expect.objectContaining({ username }))
+      })
+      expect(setGodCredentialsExpiry).toHaveBeenCalledWith(1000 + 60 * 60 * 1000)
+    }
+
+    nowSpy.mockRestore()
+  })
+})
diff --git a/frontends/nextjs/src/seed-data/workflows.test.ts b/frontends/nextjs/src/seed-data/workflows.test.ts
new file mode 100644
index 000000000..c4adbebaa
--- /dev/null
+++ b/frontends/nextjs/src/seed-data/workflows.test.ts
@@ -0,0 +1,54 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest'
+
+const { getWorkflows, addWorkflow } = vi.hoisted(() => ({
+  getWorkflows: vi.fn(),
+  addWorkflow: vi.fn(),
+}))
+
+vi.mock('@/lib/database', () => ({
+  Database: {
+    getWorkflows,
+    addWorkflow,
+  },
+}))
+
+import { initializeWorkflows } from '@/seed-data/workflows'
+
+const expectedWorkflowIds = [
+  'workflow_user_registration',
+  'workflow_page_access',
+  'workflow_comment_submission',
+]
+
+describe('initializeWorkflows', () => {
+  beforeEach(() => {
+    getWorkflows.mockReset()
+    addWorkflow.mockReset()
+  })
+
+  it.each([
+    {
+      name: 'skip seeding when workflows exist',
+      existingWorkflows: [{ id: 'existing' }],
+      expectedAdds: 0,
+    },
+    {
+      name: 'seed default workflows when none exist',
+      existingWorkflows: [],
+      expectedAdds: expectedWorkflowIds.length,
+    },
+  ])('should $name', async ({ existingWorkflows, expectedAdds }) => {
+    getWorkflows.mockResolvedValue(existingWorkflows)
+
+    await initializeWorkflows()
+
+    expect(getWorkflows).toHaveBeenCalledTimes(1)
+    expect(addWorkflow).toHaveBeenCalledTimes(expectedAdds)
+
+    if (expectedAdds > 0) {
+      expectedWorkflowIds.forEach(id => {
+        expect(addWorkflow).toHaveBeenCalledWith(expect.objectContaining({ id }))
+      })
+    }
+  })
+})