Feature: Add Rails generator and rake task support for creating data migration test coverage

README.md

@@ -97,7 +97,6 @@ You can generate a data migration as you would a schema migration:
     rake db:structure:load:with_data               # Load both structure.sql and data_schema.rb file into the database
     rake db:version:with_data                      # Retrieves the current schema version numbers for data and schema migrations
 
-
 Tasks work as they would with the 'vanilla' db version. The 'with_data' addition to the 'db' tasks will run the task in the context of both the data and schema migrations. That is, rake db:rollback:with_data will check to see if it was a schema or data migration invoked last, and do that. Tasks invoked in that space also have an additional line of output, indicating if the action is performed on data or schema.
 
 With 'up' and 'down', you can specify the option 'BOTH', which defaults to false. Using true, will migrate both the data and schema (in the desired direction) if they both match the version provided. Again, going up, schema is given precedence. Down its data.
@@ -126,10 +125,31 @@ DataMigrate.configure do |config|
     'password' => nil,
   }
   config.spec_name = 'primary'
+
+  # Enable data_migration generator to create test files
+  config.test_generator_enabled = true      # default: false
+  config.test_generator_framework = :rspec  # default: nil (will infer framework when test support enabled)
 end
+```
+
+### Test Suite Support
+
+When `config.test_generator_enabled = true`, the `data_migration` generator will create test files for your data migrations. You can explitcly set the test framework from the `config.test_generator_framework` setting. Otherwise, this will be inferred from the detected test suite.
 
+**Setup**
+Data Migration files should be required within your respective spec_helper.rb or test_helper.rb files.
+
+```
+# spec_helper.rb
+require db/data/my_new_data_migration.rb
 ```
 
+The standard data migration Rake task will now utilize corresponding RSpec and Minitest templates.
+For example, if you run `rails g data_migration add_this_to_that`, the following files will be created:
+
+- `/spec/db/data/add_this_to_that_spec.rb` (for RSpec)
+- `/test/db/data/add_this_to_that_test.rb` (for Minitest)
+
 ## Capistrano Support
 
 The gem comes with a capistrano task that can be used instead of `capistrano/rails/migrations`.

lib/data_migrate.rb

@@ -9,6 +9,7 @@
 require File.join(File.dirname(__FILE__), "data_migrate", "status_service")
 require File.join(File.dirname(__FILE__), "data_migrate", "migration_context")
 require File.join(File.dirname(__FILE__), "data_migrate", "railtie")
+require File.join(File.dirname(__FILE__), "data_migrate", "helpers/infer_test_framework")
 require File.join(File.dirname(__FILE__), "data_migrate", "tasks/data_migrate_tasks")
 require File.join(File.dirname(__FILE__), "data_migrate", "config")
 require File.join(File.dirname(__FILE__), "data_migrate", "schema_migration")

lib/data_migrate/config.rb

@@ -1,6 +1,7 @@
 module DataMigrate
-  class << self
+  include ActiveSupport::Configurable
 
+  class << self
     def configure
       yield config
     end
@@ -11,7 +12,7 @@ def config
   end
 
   class Config
-    attr_accessor :data_migrations_table_name, :data_migrations_path, :data_template_path, :db_configuration, :spec_name
+    attr_accessor :data_migrations_table_name, :data_migrations_path, :data_template_path, :db_configuration, :spec_name, :test_generator_enabled, :test_generator_framework
 
     DEFAULT_DATA_TEMPLATE_PATH = "data_migration.rb"
 
@@ -21,12 +22,20 @@ def initialize
       @data_template_path = DEFAULT_DATA_TEMPLATE_PATH
       @db_configuration = nil
       @spec_name = nil
+      @test_generator_enabled = false
+      @test_generator_framework = DataMigrate::Helpers::InferTestFramework.new.call
     end
 
     def data_template_path=(value)
       @data_template_path = value.tap do |path|
         raise ArgumentError, "File not found: '#{path}'" unless path == DEFAULT_DATA_TEMPLATE_PATH || File.exist?(path)
       end
     end
+
+    def test_generator_framework=(value)
+      raise ArgumentError, "Invalid test generator framework: #{value}" unless [:rspec, :minitest].include?(value)
+
+      @test_generator_framework = value
+    end
   end
 end

lib/data_migrate/helpers/infer_test_framework.rb

@@ -0,0 +1,15 @@
+module DataMigrate
+  module Helpers
+    class InferTestFramework
+      def call
+        if File.exist?(File.expand_path('spec/spec_helper.rb'))
+          :rspec
+        elsif File.exist?(File.expand_path('test/test_helper.rb'))
+          :minitest
+        else
+          raise StandardError.new('Unable to determine test suite')
+        end
+      end
+    end
+  end
+end

lib/generators/data_migration/data_migration_generator.rb

@@ -15,10 +15,30 @@ class DataMigrationGenerator < Rails::Generators::NamedBase
       def create_data_migration
         set_local_assigns!
         migration_template template_path, data_migrations_file_path
+        create_data_migration_test
       end
 
       protected
 
+      def create_data_migration_test
+        return unless DataMigrate.config.test_generator_enabled
+
+        case DataMigrate.config.test_generator_framework
+        when :rspec
+          template "data_migration_spec.rb", data_migrations_spec_file_path
+        when :minitest
+          template "data_migration_test.rb", data_migrations_test_file_path
+        end
+      end
+
+      def data_migrations_test_file_path
+        File.join(Rails.root, 'test', data_migrations_path, "#{migration_file_name}_test.rb")
+      end
+
+      def data_migrations_spec_file_path
+        File.join(Rails.root, 'spec', data_migrations_path, "#{migration_file_name}_spec.rb")
+      end
+
       def set_local_assigns!
         if file_name =~ /^(add|remove)_.*_(?:to|from)_(.*)/
           @migration_action = $1
@@ -38,6 +58,10 @@ def data_migrations_file_path
         File.join(data_migrations_path, "#{file_name}.rb")
       end
 
+      def data_migrations_file_path_with_version
+        File.join(data_migrations_path, "#{migration_number}_#{migration_file_name}.rb")
+      end
+
       # Use the first path in the data_migrations_path as the target directory
       def data_migrations_path
         Array.wrap(DataMigrate.config.data_migrations_path).first

lib/generators/data_migration/templates/data_migration_spec.rb

@@ -0,0 +1,10 @@
+require 'rails_helper'
+require './<%= data_migrations_file_path_with_version %>'
+
+describe <%= migration_class_name %>, type: :data_migration do
+  let(:migration) { <%= migration_class_name %>.new }
+
+  pending "should test `migration.up`"
+
+  pending "should test `migration.down`"
+end

lib/generators/data_migration/templates/data_migration_test.rb

@@ -0,0 +1,16 @@
+require 'test_helper'
+require './<%= data_migrations_file_path_with_version %>'
+
+class <%= migration_class_name %>Test < ActiveSupport::TestCase
+  def setup
+    @migration = <%= migration_class_name %>.new
+  end
+
+  def test_migration_up
+    skip("Pending test coverage for @migration.up")
+  end
+
+  def test_migration_down
+    skip("Pending test coverage for @migration.down")
+  end
+end

spec/data_migrate/config_spec.rb

@@ -66,4 +66,28 @@
       end
     end
   end
+
+  describe "#test_generator_framework=" do
+    context "when valid test framework is set" do
+      it "sets the test framework" do
+        allow(DataMigrate.config).to receive(:test_generator_framework).and_return(:minitest)
+
+        expect(DataMigrate.config.test_generator_framework).to eq(:minitest)
+      end
+    end
+
+    context "when valid test framework is set" do
+      it "sets the test framework" do
+        allow(DataMigrate.config).to receive(:test_generator_framework).and_return(:rspec)
+
+        expect(DataMigrate.config.test_generator_framework).to eq(:rspec)
+      end
+    end
+
+    context "when invalid test framework is set" do
+      it "raises an error" do
+        expect { DataMigrate.config.test_generator_framework = :invalid }.to raise_error(ArgumentError, "Invalid test generator framework: invalid")
+      end
+    end
+  end
 end

spec/data_migrate/helpers/infer_test_framework_spec.rb

@@ -0,0 +1,44 @@
+require 'spec_helper'
+
+describe DataMigrate::Helpers::InferTestFramework do
+  subject(:infer_test_suite) { described_class.new }
+
+  describe '#call' do
+    before do
+      allow(Rails).to receive(:root).and_return(Pathname.new('/fake/path'))
+    end
+
+    context 'when RSpec is detected' do
+      before do
+        allow(File).to receive(:exist?).with(File.expand_path('spec/spec_helper.rb')).and_return(true)
+        allow(File).to receive(:exist?).with(File.expand_path('test/test_helper.rb')).and_return(false)
+      end
+
+      it 'returns :rspec' do
+        expect(infer_test_suite.call).to eq(:rspec)
+      end
+    end
+
+    context 'when Minitest is detected' do
+      before do
+        allow(File).to receive(:exist?).with(File.expand_path('spec/spec_helper.rb')).and_return(false)
+        allow(File).to receive(:exist?).with(File.expand_path('test/test_helper.rb')).and_return(true)
+      end
+
+      it 'returns :minitest' do
+        expect(infer_test_suite.call).to eq(:minitest)
+      end
+    end
+
+    context 'when no test suite is detected' do
+      before do
+        allow(File).to receive(:exist?).with(File.expand_path('spec/spec_helper.rb')).and_return(false)
+        allow(File).to receive(:exist?).with(File.expand_path('test/test_helper.rb')).and_return(false)
+      end
+
+      it 'raises an error' do
+        expect { infer_test_suite.call }.to raise_error(StandardError, 'Unable to determine test suite')
+      end
+    end
+  end
+end

spec/generators/data_migration/data_migration_generator_spec.rb

@@ -30,9 +30,11 @@
   end
 
   describe :create_data_migration do
-    subject { DataMigrate::Generators::DataMigrationGenerator.new(['my_migration']) }
+    let(:migration_name) { 'my_migration' }
 
-    let(:data_migrations_file_path) { 'abc/my_migration.rb' }
+    subject { DataMigrate::Generators::DataMigrationGenerator.new([migration_name]) }
+
+    let(:data_migrations_file_path) { "abc/#{migration_name}.rb" }
 
     context 'when custom data migrations path has a trailing slash' do
       before do
@@ -44,6 +46,8 @@
           'data_migration.rb', data_migrations_file_path
         )
 
+        expect(subject).not_to receive(:template)
+
         subject.create_data_migration
       end
     end
@@ -58,9 +62,56 @@
           'data_migration.rb', data_migrations_file_path
         )
 
+        expect(subject).not_to receive(:template)
+
         subject.create_data_migration
       end
     end
+
+    context 'when test generation is enabled' do
+      let(:rails_root) { 'dummy-app' }
+
+      before do
+        DataMigrate.config.data_migrations_path = 'db/data/'
+        DataMigrate.config.test_generator_enabled = true
+
+        allow(Rails).to receive(:root).and_return(Pathname.new(rails_root))
+      end
+
+      after(:all) do
+        FileUtils.rm_rf(Dir.pwd + '/db/data')
+      end
+
+      context 'and the test suite is RSpec' do
+        before do
+          DataMigrate.config.test_generator_framework = :rspec
+        end
+
+        it 'creates a spec file' do
+          expect(subject).to receive(:template).with(
+            'data_migration_spec.rb',
+            "#{rails_root}/spec/db/data/#{migration_name}_spec.rb"
+          )
+
+          subject.create_data_migration
+        end
+      end
+
+      context 'and the test suite is Minitest' do
+        before do
+          DataMigrate.config.test_generator_framework = :minitest
+        end
+
+        it 'creates a test file' do
+          expect(subject).to receive(:template).with(
+            'data_migration_test.rb',
+            "#{rails_root}/test/db/data/#{migration_name}_test.rb"
+          )
+
+          subject.create_data_migration
+        end
+      end
+    end
   end
 
   describe ".source_root" do