Add comprehensive tests for Data class

Created test suite for previously untested Data class covering:

Initialization:
- Dictionary loading (5 expected dictionaries)
- Adjacency graph loading (4 expected graphs)
- Trie building for all dictionaries
- Graph statistics pre-computation

Graph statistics:
- Verification of average_degree values
- Verification of starting_positions values
- Correctness checks for qwerty and keypad

Ranked dictionaries:
- Word ranking verification
- Common password frequency checks

Custom word lists:
- Dictionary addition via add_word_list
- Trie generation for custom dictionaries
- Word searchability via tries
- Empty list handling

Test count increased from 271 to 291 examples (20 new tests).

Author: orien

spec/data_spec.rb

@@ -0,0 +1,130 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Zxcvbn::Data do
+  let(:data) { described_class.new }
+
+  describe '#initialize' do
+    it 'loads ranked dictionaries' do
+      expect(data.ranked_dictionaries).to be_a(Hash)
+      expect(data.ranked_dictionaries).not_to be_empty
+    end
+
+    it 'loads all expected dictionaries' do
+      expect(data.ranked_dictionaries.keys).to include('english', 'female_names', 'male_names', 'passwords', 'surnames')
+    end
+
+    it 'loads adjacency graphs' do
+      expect(data.adjacency_graphs).to be_a(Hash)
+      expect(data.adjacency_graphs).not_to be_empty
+    end
+
+    it 'loads expected adjacency graphs' do
+      expect(data.adjacency_graphs.keys).to include('qwerty', 'dvorak', 'keypad', 'mac_keypad')
+    end
+
+    it 'builds dictionary tries' do
+      expect(data.dictionary_tries).to be_a(Hash)
+      expect(data.dictionary_tries).not_to be_empty
+    end
+
+    it 'builds tries for all dictionaries' do
+      expect(data.dictionary_tries.keys).to match_array(data.ranked_dictionaries.keys)
+    end
+
+    it 'creates Trie objects' do
+      data.dictionary_tries.each_value do |trie|
+        expect(trie).to be_a(Zxcvbn::Trie)
+      end
+    end
+
+    it 'computes graph statistics' do
+      expect(data.graph_stats).to be_a(Hash)
+      expect(data.graph_stats).not_to be_empty
+    end
+
+    it 'computes stats for all graphs' do
+      expect(data.graph_stats.keys).to match_array(data.adjacency_graphs.keys)
+    end
+
+    it 'includes average_degree in graph stats' do
+      data.graph_stats.each_value do |stats|
+        expect(stats).to have_key(:average_degree)
+        expect(stats[:average_degree]).to be_a(Float)
+        expect(stats[:average_degree]).to be > 0
+      end
+    end
+
+    it 'includes starting_positions in graph stats' do
+      data.graph_stats.each_value do |stats|
+        expect(stats).to have_key(:starting_positions)
+        expect(stats[:starting_positions]).to be_a(Integer)
+        expect(stats[:starting_positions]).to be > 0
+      end
+    end
+  end
+
+  describe '#ranked_dictionaries' do
+    it 'returns dictionaries with word rankings' do
+      dict = data.ranked_dictionaries['english']
+      expect(dict).to be_a(Hash)
+      expect(dict.values.first).to be_a(Integer)
+    end
+
+    it 'ranks common words lower (more frequent)' do
+      dict = data.ranked_dictionaries['passwords']
+      # Common passwords should have low rank numbers
+      expect(dict['password']).to be_a(Integer)
+      expect(dict['password']).to be < 100
+    end
+  end
+
+  describe '#add_word_list' do
+    it 'adds a custom dictionary' do
+      data.add_word_list('custom', %w[foo bar baz])
+      expect(data.ranked_dictionaries).to have_key('custom')
+    end
+
+    it 'ranks the custom dictionary' do
+      data.add_word_list('custom', %w[foo bar baz])
+      dict = data.ranked_dictionaries['custom']
+      expect(dict['foo']).to be_a(Integer)
+      expect(dict['bar']).to be_a(Integer)
+      expect(dict['baz']).to be_a(Integer)
+    end
+
+    it 'builds a trie for the custom dictionary' do
+      data.add_word_list('custom', %w[foo bar baz])
+      expect(data.dictionary_tries).to have_key('custom')
+      expect(data.dictionary_tries['custom']).to be_a(Zxcvbn::Trie)
+    end
+
+    it 'makes custom words searchable via trie' do
+      data.add_word_list('custom', %w[test])
+      trie = data.dictionary_tries['custom']
+      results = trie.search_prefixes('testing', 0)
+      expect(results).not_to be_empty
+      expect(results.first[0]).to eq('test')
+    end
+
+    it 'handles empty word lists' do
+      data.add_word_list('empty', [])
+      expect(data.ranked_dictionaries['empty']).to be_empty
+    end
+  end
+
+  describe '#graph_stats' do
+    it 'has correct values for qwerty keyboard' do
+      stats = data.graph_stats['qwerty']
+      expect(stats[:average_degree]).to be_within(0.01).of(4.6)
+      expect(stats[:starting_positions]).to eq(94)
+    end
+
+    it 'has correct values for keypad' do
+      stats = data.graph_stats['keypad']
+      expect(stats[:average_degree]).to be_within(0.01).of(5.07)
+      expect(stats[:starting_positions]).to eq(15)
+    end
+  end
+end