Add fix to access the plugin inside tests

[SumeetHaryani]

Checklist

• [x] run npm run test and npm run benchmark
• [ ] tests and/or benchmarks are included
• [ ] documentation is changed or added
• [ ] commit message and code follows the Developer's Certification of Origin and the Code of conduct

[SumeetHaryani]

@Eomm By wrapping the build function with fastify-plugin able to access the plugins inside test cases. Should I add changes for other configurations?