How to Write a GROQ Join Query for a Reference Type

export default {
  name: 'homepage',
  type: 'document',
  title: 'Homepage Data',
  fields: [
    ...
    {
      name: 'home_testimonials',
      type: 'array',
      of: [{ type: 'reference', to: [{ type: 'testimonial' }] }],
      title: 'Homepage Testimonials',
    },
  ],
}; 

// testimonial.js
export default {
  name: 'testimonial',
  title: 'Testimonial',
  type: 'document',
  fields: [
    {
      name: 'author',
      type: 'string',
      title: 'Author',
    },
    {
      name: 'jobTitle',
      type: 'string',
      title: 'Job Title',
    },
    {
      name: 'content',
      type: 'string',
      title: 'Content',
    },
  ],
};

export const homepageQuery = `*[_type == "homepage"] {
  ...,
  "home_testimonials": testimonial[]{
    testimonial->{content, jobTitle, author}
  }
}`;

home_testimonials: [{
  "_key":"4185e4bd9cea",
  "_ref":"07c6f4c5-f09b-456b-9d1b-95af390f389b",
  "_type":"reference"
  },
  ...
] 

*[ _type == "homepage" ]{ ..., home_testimonials[]->{content, jobTitle, author} }