Add tests for absent anonymizer and residential data

horgh's review of the anonymizer.residential addition flagged two
untested paths:

- Insights#initialize unconditionally calls
  Anonymizer.new(record['anonymizer']), and Anonymizer#initialize
  unconditionally calls AnonymizerFeed.new(record['residential']). The
  common case has neither key present, so Anonymizer.new(nil) and
  AnonymizerFeed.new(nil) are the hot paths, guarded only by
  `record.nil? ? nil : record['residential']`. Add coverage for a
  Model::Insights built from a raw hash with no "anonymizer" key at
  all, and for an "anonymizer" present without a nested "residential"
  key, asserting every getter returns nil with no NoMethodError.

- network_last_seen's `if !date_string` guard, which prevents
  Date.parse(nil) from raising when the date key is absent, was
  untested in all three places it is duplicated: AnonymizerFeed,
  Anonymizer, and Model::AnonymousPlus. Add a test per class
  asserting network_last_seen is nil when the date key is absent.

Verified the AnonymizerFeed test actually catches a regression: with
the guard temporarily removed (network_last_seen calling
Date.parse(date_string) unconditionally), 3 of the 5 new tests failed
with "TypeError: no implicit conversion of nil into String" as
expected. Restored the guard afterward.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: oschwald

test/test_record.rb

@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+require 'date'
+require 'maxmind/geoip2'
+require 'minitest/autorun'
+
+class RecordTest < Minitest::Test
+  # This covers the common case where a web service response has no
+  # "anonymizer" key at all. Insights#initialize always calls
+  # Anonymizer.new(record['anonymizer']), so this exercises
+  # Anonymizer.new(nil) and, in turn, AnonymizerFeed.new(nil).
+  def test_insights_no_anonymizer
+    model = MaxMind::GeoIP2::Model::Insights.new({}, ['en'])
+
+    assert_nil(model.anonymizer.confidence)
+    refute(model.anonymizer.anonymous?)
+    refute(model.anonymizer.anonymous_vpn?)
+    refute(model.anonymizer.hosting_provider?)
+    refute(model.anonymizer.public_proxy?)
+    refute(model.anonymizer.residential_proxy?)
+    refute(model.anonymizer.tor_exit_node?)
+    assert_nil(model.anonymizer.network_last_seen)
+    assert_nil(model.anonymizer.provider_name)
+
+    assert_nil(model.anonymizer.residential.confidence)
+    assert_nil(model.anonymizer.residential.network_last_seen)
+    assert_nil(model.anonymizer.residential.provider_name)
+  end
+
+  # This covers an "anonymizer" object being present without a nested
+  # "residential" key, which is the common case when the network is not
+  # part of the residential proxy feed.
+  def test_insights_anonymizer_without_residential
+    model = MaxMind::GeoIP2::Model::Insights.new(
+      {
+        'anonymizer' => {
+          'confidence' => 85,
+        },
+      },
+      ['en'],
+    )
+
+    assert_equal(85, model.anonymizer.confidence)
+
+    assert_nil(model.anonymizer.residential.confidence)
+    assert_nil(model.anonymizer.residential.network_last_seen)
+    assert_nil(model.anonymizer.residential.provider_name)
+  end
+
+  # network_last_seen is parsed lazily and guards against a missing date
+  # string. This asserts the guard is in place rather than an unconditional
+  # Date.parse(nil), which would raise.
+  def test_anonymizer_feed_network_last_seen_absent
+    feed = MaxMind::GeoIP2::Record::AnonymizerFeed.new(
+      { 'confidence' => 82 },
+    )
+
+    assert_nil(feed.network_last_seen)
+  end
+
+  def test_anonymizer_network_last_seen_absent
+    anonymizer = MaxMind::GeoIP2::Record::Anonymizer.new(
+      { 'confidence' => 85 },
+    )
+
+    assert_nil(anonymizer.network_last_seen)
+  end
+
+  def test_anonymous_plus_network_last_seen_absent
+    model = MaxMind::GeoIP2::Model::AnonymousPlus.new(
+      {
+        'ip_address' => '1.2.3.4',
+        'prefix_length' => 24,
+      },
+    )
+
+    assert_nil(model.network_last_seen)
+  end
+end