Using rspec-rails in non-rails projects

require_rails_all.rb

ActiveRecord::ConnectionNotEstablished: No connection pool with 'primary' found.
-e:1:in `load'
-e:1:in `<main>'

require_rspec_rails.rb

An error occurred while loading ./spec/project/project_spec.rb.
Failure/Error: require 'rspec/rails'

NameError:
  uninitialized constant ActionView::Template::Handlers::ERB::ENCODING_FLAG
  Did you mean?  Encoding
# ./spec/spec_helper.rb:9:in `require'
# ./spec/spec_helper.rb:9:in `<top (required)>'
# ./spec/project/project_spec.rb:1:in `require'
# ./spec/project/project_spec.rb:1:in `<top (required)>'
# -e:1:in `load'
# -e:1:in `<main>'

rspec_error_handling.rb

expect {
  Job.perform_later
}.to have_fgkjbfvghfjk(Job)

# => You must pass an argument rather than a block to use the provided matcher (have fgkjbfvghfjk Job), or the matcher must implement `supports_block_expectations?`.

expect {
  Job.perform_later
}.to fgkjbfvghfjk(Job)

# => NoMethodError: undefined method `fgkjbfvghfjk' for #<RSpec::ExampleGroups::Something:0x007f827dab4170>

rspec_rails_missing.rb

expect(Job).to have_been_enqueued

# => expected Job to respond to `has_been_enqueued?`

expect {
  Job.perform_later
}.to have_enqueued_job(Job)

# => You must pass an argument rather than a block to use the provided matcher (have enqueued job Job), or the matcher must implement `supports_block_expectations?`.

spec_helper.rb

require "action_controller/railtie"