diff --git a/docker-compose.yml b/docker-compose.yml
index 5769116..9316df5 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -31,19 +31,6 @@ services:
       - solr-sdr-catalog
       - mariadb
 
-  test-persist:
-    build: .
-    volumes:
-      - .:/usr/src/app
-      - gem_cache:/gems
-    command: bash -c "bin/wait-for solr-sdr-catalog:9033 mariadb:3306"
-    environment:
-      SOLR_URL: http://solr-sdr-catalog:9033/solr/catalog
-      RIGHTS_DATABASE_CONNECTION_STRING: "mysql2://ht_rights:ht_rights@mariadb/ht"
-    depends_on:
-      - solr-sdr-catalog
-      - mariadb
-
   solr-sdr-catalog:
     image: ghcr.io/hathitrust/catalog-solr-sample
     ports:
diff --git a/lib/oai_solr/basic_marc_extractor.rb b/lib/oai_solr/basic_marc_extractor.rb
index 73e87e1..ca4a69b 100644
--- a/lib/oai_solr/basic_marc_extractor.rb
+++ b/lib/oai_solr/basic_marc_extractor.rb
@@ -71,8 +71,8 @@ def values(rec)
     # merge into one set; the ranges we handle separately for efficiency (no sense in
     # turning '600'..'699' into an array)
     def set_interesting_tags!
-      @interesting_single_tags = Set.new
-      @interesting_ranges = Set.new
+      @interesting_single_tags = ::Set.new
+      @interesting_ranges = ::Set.new
       @single_extractors.map(&:computed_tags).each do |tags|
         case tags
         when Range
diff --git a/lib/oai_solr/basic_marc_single_extractor.rb b/lib/oai_solr/basic_marc_single_extractor.rb
index 6081f60..97775c9 100644
--- a/lib/oai_solr/basic_marc_single_extractor.rb
+++ b/lib/oai_solr/basic_marc_single_extractor.rb
@@ -110,7 +110,7 @@ def tag_matcher(tags_to_match)
         @computed_tags = tags_to_match
         ->(t) { @computed_tags.cover?(t) }
       else
-        raise "Illegal argumrnt '#{tags_to_match.inspect}'"
+        raise "Illegal argument '#{tags_to_match.inspect}'"
       end
     end
 
diff --git a/lib/oai_solr/dublin_core_crosswalk.rb b/lib/oai_solr/dublin_core_crosswalk.rb
index 0f0a51b..114c23d 100644
--- a/lib/oai_solr/dublin_core_crosswalk.rb
+++ b/lib/oai_solr/dublin_core_crosswalk.rb
@@ -82,31 +82,17 @@ class DublinCoreCrosswalk
       # type -- see below
     }
 
-    # Build the instance that will do the data extraction based on the mappings
-    # in MAPPINGS.
-    def initialize
-      MAPPINGS.each_pair do |key, spec_pairs|
-        define_singleton_method(key.to_sym, basic_marc_extractor_proc(spec_pairs))
-      end
+    MAPPINGS.each do |key, spec_pairs|
+      bme = BasicMARCExtractor.from_pairs(spec_pairs)
+      define_method(key.to_sym, ->(rec) { bme.values(rec) })
     end
 
+    # If it's necessary to add a field that does not have an identically-named
+    # accessor, or is not in MAPPINGS, some adjustment may be necessary,
     def full_map(rec)
-      {
-        contributor: contributor(rec),
-        coverage: coverage(rec),
-        date: date(rec),
-        description: description(rec),
-        format: self.format(rec), # need self to avoid keyword conflict
-        identifier: identifier(rec),
-        language: language(rec),
-        publisher: publisher(rec),
-        relation: relation(rec),
-        rights: rights(rec),
-        source: source(rec),
-        subject: subject(rec),
-        title: title(rec),
-        type: type(rec)
-      }.reject { |k, v| v.empty? }
+      fields = MAPPINGS.keys + %i(type date)
+      Hash[fields.map {|field| [ field, self.send(field, rec)] }]
+        .reject { |k, v| v.empty? }
     end
 
     # Get the best date possible, looking for four digits in the 008, then
@@ -138,11 +124,6 @@ def type(rec)
 
     private
 
-    def basic_marc_extractor_proc(pairs)
-      bme = BasicMARCExtractor.from_pairs(pairs)
-      ->(rec) { bme.values(rec) }
-    end
-
     def date_008(rec)
       rec["008"].value[7..10]
     end