Validate test fixture attributes

lib/frozen_record/test_helper.rb

@@ -2,6 +2,7 @@
 
 module FrozenRecord
   module TestHelper
+    FixtureAttributeMismatch = Class.new(StandardError)
     NoFixturesLoaded = Class.new(StandardError)
 
     class << self
@@ -15,10 +16,16 @@ def load_fixture(model_class, alternate_base_path)
           unload_fixture(model_class)
         end
 
-        @cache[model_class] = base_path_if_file_present(model_class)
+        old_base_path = base_path_if_file_present(model_class)
+        expected_attributes = model_class.attributes if old_base_path
+        @cache[model_class] = old_base_path
 
         model_class.base_path = alternate_base_path
         model_class.load_records(force: true)
+        ensure_fixture_attributes_match(model_class, expected_attributes) if expected_attributes
+      rescue FixtureAttributeMismatch
+        unload_fixture(model_class)
+        raise
       end
 
       def unload_fixture(model_class)
@@ -62,6 +69,19 @@ def ensure_model_class_is_frozenrecord(model_class)
           raise ArgumentError, "Model class (#{model_class}) does not inherit from #{FrozenRecord::Base}"
         end
       end
+
+      def ensure_fixture_attributes_match(model_class, expected_attributes)
+        actual_attributes = model_class.attributes
+        missing_attributes = expected_attributes - actual_attributes
+        unexpected_attributes = actual_attributes - expected_attributes
+        return if missing_attributes.empty? && unexpected_attributes.empty?
+
+        differences = []
+        differences << "missing: #{missing_attributes.to_a.sort.join(', ')}" unless missing_attributes.empty?
+        differences << "unexpected: #{unexpected_attributes.to_a.sort.join(', ')}" unless unexpected_attributes.empty?
+
+        raise FixtureAttributeMismatch, "#{model_class} fixture attributes do not match (#{differences.join('; ')})"
+      end
     end
   end
 end

spec/fixtures/test_helper/countries.yml.erb

@@ -6,4 +6,6 @@
   population: 42
   founded_on: 2019-01-01
   updated_at: 2019-01-01T19:08:06-05:00
+  nato: true
   king: Bob Smith
+  continent: Some continent

spec/fixtures/test_helper/missing_attributes/countries.yml.erb

@@ -0,0 +1,10 @@
+---
+- id: 1
+  name: Some country
+  capital: <%= 'Somewhere' %>
+  density: 1.0
+  population: 42
+  founded_on: 2019-01-01
+  updated_at: 2019-01-01T19:08:06-05:00
+  king: Bob Smith
+  continent: Some continent

spec/fixtures/test_helper/unexpected_attributes/countries.yml.erb

@@ -0,0 +1,12 @@
+---
+- id: 1
+  name: Some country
+  capital: <%= 'Somewhere' %>
+  density: 1.0
+  population: 42
+  founded_on: 2019-01-01
+  updated_at: 2019-01-01T19:08:06-05:00
+  nato: true
+  king: Bob Smith
+  continent: Some continent
+  region_code: SC

spec/test_helper_spec.rb

@@ -24,6 +24,36 @@
       }.to raise_error(ArgumentError)
     end
 
+    it 'raises when alternate fixtures are missing attributes' do
+      original_base_path = Country.base_path
+      test_fixtures_base_path = File.join(File.dirname(__FILE__), 'fixtures', 'test_helper', 'missing_attributes')
+
+      expect {
+        FrozenRecord::TestHelper.load_fixture(Country, test_fixtures_base_path)
+      }.to raise_error(
+        FrozenRecord::TestHelper::FixtureAttributeMismatch,
+        'Country fixture attributes do not match (missing: nato)'
+      )
+
+      expect(Country.base_path).to eq(original_base_path)
+      expect(Country.count).to be == 3
+    end
+
+    it 'raises when alternate fixtures have unexpected attributes' do
+      original_base_path = Country.base_path
+      test_fixtures_base_path = File.join(File.dirname(__FILE__), 'fixtures', 'test_helper', 'unexpected_attributes')
+
+      expect {
+        FrozenRecord::TestHelper.load_fixture(Country, test_fixtures_base_path)
+      }.to raise_error(
+        FrozenRecord::TestHelper::FixtureAttributeMismatch,
+        'Country fixture attributes do not match (unexpected: region_code)'
+      )
+
+      expect(Country.base_path).to eq(original_base_path)
+      expect(Country.count).to be == 3
+    end
+
     it 'is a no-op when called again with the same path' do
       test_fixtures_base_path = File.join(File.dirname(__FILE__), 'fixtures', 'test_helper')
       FrozenRecord::TestHelper.load_fixture(Country, test_fixtures_base_path)