Add specs for feature_flags_available? method

spec/lib/feature_spec.rb

@@ -11,6 +11,32 @@ RSpec.describe Feature, stub_feature_flags: false do
     skip_feature_flags_yaml_validation
   end
 
+  describe '.feature_flags_available?' do
+    it 'returns false on connection error' do
+      expect(ActiveRecord::Base.connection).to receive(:active?).and_raise(PG::ConnectionBad) # rubocop:disable Database/MultipleDatabases
+
+      expect(described_class.feature_flags_available?).to eq(false)
+    end
+
+    it 'returns false when connection is not active' do
+      expect(ActiveRecord::Base.connection).to receive(:active?).and_return(false) # rubocop:disable Database/MultipleDatabases
+
+      expect(described_class.feature_flags_available?).to eq(false)
+    end
+
+    it 'returns false when the flipper table does not exist' do
+      expect(Feature::FlipperFeature).to receive(:table_exists?).and_return(false)
+
+      expect(described_class.feature_flags_available?).to eq(false)
+    end
+
+    it 'returns false on NoDatabaseError' do
+      expect(Feature::FlipperFeature).to receive(:table_exists?).and_raise(ActiveRecord::NoDatabaseError)
+
+      expect(described_class.feature_flags_available?).to eq(false)
+    end
+  end
+
   describe '.get' do
     let(:feature) { double(:feature) }
     let(:key) { 'my_feature' }