Cypress using JSON fixture in body?

You get a literal because in the form cy.request(options), options is a plain JS object and unfortunately not parsed by Cypress to interpret the alias.

The request form cy.request(method, url, body) probably does allow an alias for the body param, since cy.route() allows it ref: Accessing Fixture Data

e.g the following should be valid, but does not allow setting headers

cy.fixture('test_create').as('create_test')
cy.request('POST', 'http://localhost:8080/widgets', '@create_test');

So, you can use then()

cy.fixture('test_create').then(myFixture => {

  cy.request({
    method: 'POST',
    url: 'http://localhost:8080/widgets',
    body: myFixture,
    headers: {
      'Authorization': this.token,
      'Content-Type': 'application/json;charset=UTF-8'
    }
  })
});

or

cy.fixture('test_create').as('create_test');

...  // some other code between

cy.get('@create_test').then(myFixture => {  // retrieve the fixture from alias

  cy.request({
    method: 'POST',
    url: 'http://localhost:8080/widgets',
    body: myFixture,
    headers: {
      'Authorization': this.token,
      'Content-Type': 'application/json;charset=UTF-8'
    }
  })
})