that seems like it's probably the wrong url to be POSTing to, assuming you are doing normal REST routes, you'd be GETting that (if you expect to see a form), or POSTing to /business/customers if you have already filled out the form and are actually trying to create the record
beingjohnm: ruby has no mechanism to do warnings like that in core, and you are providing no hints that would cause it to think you want floats. you specify 2 integers and ask to do division, it does integer division.
maybe in version 3 the default could be changed. a discussion in the ruby-lang mailing list might get some progress down that regard, or some more clear technical reasons why integer division is the default
2 options are app/services and lib/ depending on the specific nature of the code
hrmm, trying to fix an issue in one of my environments where `bin/rails c` complains that rake isn't installed, but `bundle show rake` shows it as being installed, and `bundle install` doesn't do anything and lists it as already installed. Not sure where else to look for mixup
at unit level, you need both negative and positive assertions for cases
here's some more information based on the theory of the testing pyramid: https://martinfowler.com/articles/practical-test-pyramid.html#WhatToTest
guess it depends on what is necessary business logic wise to generate the preview
if it's just a reification of the CSV file, then upload the CSV to some sort of centralized object store like S3. if you need to do a lot of processing, consider doing the same thing if you can stand the request overhead, or put the work into a background job with a status checker. alternatively create a temporary table to store the data.