Update to Minitest 6; update testing dependencies; add and configure simplecov

Author: rameerez

.simplecov

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+# SimpleCov configuration file (auto-loaded before test suite)
+# This keeps test_helper.rb clean and follows best practices
+
+SimpleCov.start do
+  # Use SimpleFormatter for terminal-only output (no HTML generation)
+  formatter SimpleCov::Formatter::SimpleFormatter
+
+  # Track coverage for the lib directory (gem source code)
+  add_filter "/test/"
+
+  # Exclude Rails engine components that require integration testing
+  # These are tested via Appraisal with a full Rails app
+  add_filter "/lib/profitable/engine.rb"
+  add_filter "/app/"
+
+  # Exclude the main profitable.rb entry point - it loads the engine and
+  # defines the Profitable module. Our unit tests use a test-specific
+  # Profitable module (defined in test_helper.rb) to avoid Rails dependencies.
+  # The core logic is tested via the individual lib/profitable/*.rb files.
+  add_filter "/lib/profitable.rb"
+
+  # Track the lib directory (core gem logic)
+  track_files "lib/**/*.rb"
+
+  # Enable branch coverage for more detailed metrics
+  enable_coverage :branch
+
+  # Set minimum coverage threshold for the core calculation logic
+  # The Rails engine/controllers are tested separately via Appraisal
+  minimum_coverage line: 80, branch: 70
+
+  # Disambiguate parallel test runs
+  command_name "Job #{ENV['TEST_ENV_NUMBER']}" if ENV['TEST_ENV_NUMBER']
+end
+
+# Print coverage summary to terminal after tests complete
+SimpleCov.at_exit do
+  SimpleCov.result.format!
+  puts "\n" + "=" * 60
+  puts "COVERAGE SUMMARY"
+  puts "=" * 60
+  puts "Line Coverage:   #{SimpleCov.result.covered_percent.round(2)}%"
+  puts "Branch Coverage: #{SimpleCov.result.coverage_statistics[:branch]&.percent&.round(2) || 'N/A'}%"
+  puts "=" * 60
+end

Gemfile

@@ -2,20 +2,21 @@
 
 source "https://rubygems.org"
 
-# Specify your gem's dependencies in profitable.gemspec
+# Specify your gem's dependencies in slugifiable.gemspec
 gemspec
 
 gem "rake", "~> 13.0"
 
-group :development do
-  gem "appraisal", "~> 2.5"
-end
+group :development, :test do
+  gem "appraisal"
+  gem "minitest", "~> 6.0"
+  gem "minitest-mock"
+  gem "minitest-reporters"
+  gem "rack-test"
+  gem "simplecov", require: false
+  gem "sqlite3", ">= 2.1"
 
-group :test do
-  gem "minitest", "~> 5.0"
-  gem "minitest-reporters", "~> 1.6"
   gem "mocha", "~> 2.1"
   gem "activerecord", ">= 7.0"
   gem "actionview", ">= 7.0"
-  gem "sqlite3"
 end

test/test_helper.rb

@@ -2,11 +2,16 @@
 
 $LOAD_PATH.unshift File.expand_path("../lib", __dir__)
 
+# SimpleCov must be loaded BEFORE any application code
+# Configuration is auto-loaded from .simplecov file
+require "simplecov"
+
 require "bundler/setup"
 require "active_record"
 require "active_support/all"
 require "action_view"
 require "minitest/autorun"
+require "minitest/mock"
 require "minitest/reporters"
 require "mocha/minitest"