chore: --init-next improvements and tests

test/create-payload-app/.gitignore

@@ -0,0 +1 @@
+test-app

test/create-payload-app/int.spec.ts

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+import fs from 'fs'
+import path from 'path'
+import shelljs from 'shelljs'
+
+import { initNext } from '../../packages/create-payload-app/src/lib/init-next'
+
+describe('create-payload-app', () => {
+  describe('--init-next', () => {
+    const nextDir = path.resolve(__dirname, 'test-app')
+
+    beforeAll(() => {
+      if (fs.existsSync(nextDir)) {
+        fs.rmdirSync(nextDir, { recursive: true })
+      }
+
+      // Create dir for Next.js project
+      if (!fs.existsSync(nextDir)) {
+        fs.mkdirSync(nextDir)
+      }
+
+      // Create a new Next.js project with default options
+      shelljs.exec(
+        'pnpm create next-app@latest . --typescript --eslint --no-tailwind --app --import-alias="@/*" --src-dir',
+        { cwd: nextDir },
+      )
+    })
+
+    afterAll(() => {
+      if (fs.existsSync(nextDir)) {
+        fs.rmdirSync(nextDir, { recursive: true })
+      }
+    })
+
+    it('should install payload app in Next.js project', async () => {
+      expect(fs.existsSync(nextDir)).toBe(true)
+
+      const result = await initNext({
+        '--debug': true,
+        nextDir,
+        useDistFiles: true, // create-payload-app must be built
+      })
+
+      expect(result.success).toBe(true)
+      const payloadFilesPath = path.resolve(nextDir, 'src/app/(payload)')
+      expect(fs.existsSync(payloadFilesPath)).toBe(true)
+    })
+  })
+})