wip variant service test

test/fixtures/files/dan-gold@2x.jpeg

test/fixtures/files/dan-gold_1000x500_crop_left.jpeg

test/fixtures/files/dan-gold_200x300_crop_top.jpeg

test/fixtures/files/dan-gold_250x250@3x.jpeg

test/fixtures/files/dan-gold_250x250_crop_left@2x.jpeg

test/fixtures/files/dan-gold_300x200_crop_right@2x.jpeg

test/fixtures/files/dan-gold_500x.jpeg

test/fixtures/files/dan-gold_500x500.jpeg

test/fixtures/files/dan-gold_500x500@2x.jpeg

test/fixtures/files/dan-gold_500x500_crop_left.jpeg

test/fixtures/files/dan-gold_crop_left.jpeg

test/fixtures/files/dan-gold_crop_left@2x.jpeg

test/fixtures/files/dan-gold_x500.jpeg

test/models/variant_service_test.rb