Part I test coverage increase for sequence migration code

app/lib/sequence_migration.rb

@@ -14,6 +14,8 @@
 #           automagically run if the API determines a sequence is out of date.
 module SequenceMigration
   class Base
+    UP_IS_REQUIRED = "You forgot to implement an `up()`" +
+                     " method on your migration"
     # When we last ran a compaction (22 NOV 17), the highest version number was
     # this:
     HIGHEST_VERSION_AT_TIME_OF_LAST_COMPACTION = 4
@@ -33,11 +35,6 @@ module SequenceMigration
       self
         .descendants
         .map  { |k| k::VERSION }
-        .each { |v|
-          if v < HIGHEST_VERSION_AT_TIME_OF_LAST_COMPACTION
-            raise "VERSION TOO LOW"
-          end
-        }
         .max
     end
 
@@ -62,7 +59,7 @@ module SequenceMigration
     end
 
     def up
-      throw "You forgot to implement an `up()` method on your migration"
+      raise UP_IS_REQUIRED
     end
 
     def run

app/models/sequence.rb

@@ -57,14 +57,6 @@ class Sequence < ApplicationRecord
     Sequences::Migrate.run!(sequence: self, device: self.device)
   end
 
-  # Helper used for QAing stuff on staging. Grabs a random sequence from the
-  # database, runs a migration (does not save) and prints to screen.
-  def self.spot_check
-    s = random
-    puts "Sequence ##{s.id} ========="
-    puts s.maybe_migrate.body.to_yaml
-  end
-
   def self.random
     Sequence.order("RANDOM()").first
   end

spec/lib/sequence_migration_spec.rb

@@ -44,6 +44,14 @@ FIXTURE = JSON.parse('[
   }
 ]')
 
+class MockMigration < SequenceMigration::Base
+  VERSION = -9
+end
+
+class MockMigrationTwo < SequenceMigration::Base
+  VERSION = 1
+end
+
 describe SequenceMigration do
   it 'has a latest version' do
       expect(SequenceMigration::Base.latest_version).to eq(5)
@@ -63,4 +71,25 @@ describe SequenceMigration do
     expect(s.body[1]["args"]["speed"]).to eq(100)
     expect(s.body[2]["args"]["speed"]).to eq(100)
   end
+
+  it 'warns developers that `up()` is required' do
+    base = SequenceMigration::Base.new(FactoryBot.create(:sequence))
+    expect { base.up }.to raise_error(SequenceMigration::Base::UP_IS_REQUIRED)
+  end
+
+  it 'checks for appropriate version number when running `before()`' do
+    base = MockMigration.new(FactoryBot.build(:sequence))
+    expect { base.before }
+      .to raise_error("Version must be -10 to run MockMigration. Got: 4")
+  end
+
+  it 'sorts migrations by version number' do
+    allow(SequenceMigration::Base)
+      .to receive(:descendants) { [MockMigration, MockMigrationTwo] }
+    sequence                 = FactoryBot.build(:sequence)
+    sequence.args["version"] = -10
+    result                   = SequenceMigration::Base.generate_list(sequence)
+    expect(result.first).to be_kind_of(MockMigration)
+    expect(result.last).to  be_kind_of(MockMigrationTwo)
+  end
 end