```ruby
require 'rails_helper'

describe Person, type: :model do
  it 'should have a valid factory' do
    expect(create(:person)).to be_valid
  end
  
  it 'requires a church' do
    expect(build(:person, church: nil)).to be_invalid
  end
  
  it 'requires first name' do
    expect(build(:person, first_name: nil)).to be_invalid
  end
  
  it 'requires last name' do
    expect(build(:person, last_name: nil)).to be_invalid
  end
  
  it 'creates a name from first and last names' do
    expect(build(:person, first_name: 'Roger', last_name: 'Smith').name).to eq('Roger Smith')
  end
  
  it 'stores arbitrary fields' do
    fields = { 'a field' => 'b', 'd' => 3, 'f' => true }
    person = build(:person, fields: fields)
    expect(person.save).to be true
    person.reload
    expect(person.fields).to eq(fields)
  end
end
```

Test that arbitrary fields can hold non-ascii characters.
user
```ruby
require 'rails_helper'

describe Person, type: :model do
  it 'should have a valid factory' do
    expect(create(:person)).to be_valid
  end
  
  it 'requires a church' do
    expect(build(:person, church: nil)).to be_invalid
  end
  
  it 'requires first name' do
    expect(build(:person, first_name: nil)).to be_invalid
  end
  
  it 'requires last name' do
    expect(build(:person, last_name: nil)).to be_invalid
  end
  
  it 'creates a name from first and last names' do
    expect(build(:person, first_name: 'Roger', last_name: 'Smith').name).to eq('Roger Smith')
  end
  
  it 'stores arbitrary fields' do
    fields = { 'a field!@#$%^&*()[]{}_-="\'' => 'b💩', 'd💩' => 3, 'f' => true }
    person = build(:person, fields: fields)
    expect(person.save).to be true
    person.reload
    expect(person.fields).to eq(fields)
  end
end
```
assistant