Switch to find_or_create_by after code review

Jeremy pointed out during code review that it might be worth using
find_or_create_by in the Term methods, rather than a combination of the
create method and a guard method in the Detection model.

This makes that change, adopting find_or_create_by inside Term and
removing the check_for_current method from the Detection model.

Along the way we update the specific assertion being looked for in the
Detection tests. Please note that there are tests in the Term model that
confirm the record_* methods an be called repeatedly without either
creating duplicate records, or throwing errors.

app/models/detection.rb

@@ -25,7 +25,7 @@ class Detection < ApplicationRecord
   belongs_to :detector
 
   # We use the before_create hook to prevent needing to override the initialize method, which Rails frowns upon.
-  before_create :set_defaults, :check_for_current
+  before_create :set_defaults
 
   # These scopes allow for easy filtering of Detection records by a single parameter.
   scope :current, -> { where(detector_version: ENV.fetch('DETECTOR_VERSION', 'unset')) }
@@ -34,15 +34,6 @@ class Detection < ApplicationRecord
 
   private
 
-  # This leverages three scopes to confirm, before creating a new Detection, whether that combination of Term, Detector,
-  # and Version has already been registered. If one is found, it aborts the creation.
-  def check_for_current
-    return unless Detection.for_term(term).for_detector(detector).current.exists?
-
-    errors.add(:detector_version, 'already exists')
-    throw(:abort)
-  end
-
   # This looks up the current Detector Version from the environment, storing the value as part of the record which is
   # about to be saved. This prevents the rest of the application from having to worry about this value, while also
   # providing a mechanism to prevent duplicate records from being created.

app/models/term.rb

@@ -35,7 +35,7 @@ def record_patterns
     si = Detector::StandardIdentifiers.new(phrase)
 
     si.identifiers.each_key do |k|
-      Detection.create(
+      Detection.find_or_create_by(
         term: self,
         detector: Detector.where(name: k.to_s.upcase).first
       )
@@ -51,7 +51,7 @@ def record_journals
     result = Detector::Journal.full_term_match(phrase)
     return unless result.any?
 
-    Detection.create(
+    Detection.find_or_create_by(
       term: self,
       detector: Detector.where("name = 'Journal'").first
     )
@@ -69,7 +69,7 @@ def record_suggested_resources
     result = Detector::SuggestedResource.full_term_match(phrase)
     return unless result.any?
 
-    Detection.create(
+    Detection.find_or_create_by(
       term: self,
       detector: Detector.where("name = 'SuggestedResource'").first
     )

test/models/detection_test.rb

@@ -28,7 +28,7 @@ class DetectionTest < ActiveSupport::TestCase
 
     assert_equal(initial_count + 1, post_count)
 
-    assert_raises(ActiveRecord::RecordNotSaved) do
+    assert_raises(ActiveRecord::RecordNotUnique) do
       Detection.create!(sample)
     end
 
@@ -48,7 +48,7 @@ class DetectionTest < ActiveSupport::TestCase
     }
 
     # A purely duplicate record fails to save...
-    assert_raises(ActiveRecord::RecordNotSaved) do
+    assert_raises(ActiveRecord::RecordNotUnique) do
       Detection.create!(new_sample)
     end