feat(formatter): first, very dirty implementation of formatter

this code is more or less broken, as-is, but it's a start to turning
this into a proper library.

lib/rspec/activerecord/formatter.rb

@@ -0,0 +1,124 @@
+class ActiveRecordFormatter < RSpec::Core::Formatters::DocumentationFormatter
+  # This registers the notifications this formatter supports, and tells
+  # us that this was written against the RSpec 3.x formatter API.
+  RSpec::Core::Formatters.register self, :example_started, :example_passed,
+                                         :example_failed, :start, :dump_summary
+
+  def initialize(output)
+    super
+    @colorizer = ::RSpec::Core::Formatters::ConsoleCodes
+  end
+
+  def start(start_notification)
+    ActiveRecordProfiler.init
+
+    output.puts "Recording and reporting ActiveRecord select and creation counts."
+  end
+
+  def example_started(example)
+    ActiveRecordProfiler.reset_example
+  end
+
+  def dump_summary(summary)
+    formatted = "\nFinished in #{summary.formatted_duration} " \
+      "(files took #{summary.formatted_load_time} to load)\n" \
+      "#{colorized_expanded_totals(summary)}\n"
+
+    unless summary.failed_examples.empty?
+      formatted << summary.colorized_rerun_commands(@colorizer) << "\n"
+    end
+
+    output.puts formatted
+  end
+
+  protected
+
+  def passed_output(example)
+    "#{current_indentation}#{ActiveRecordProfiler.example_counts}" +
+      @colorizer.wrap(example.description.strip, :success)
+  end
+
+  def failure_output(example)
+    "#{current_indentation}#{ActiveRecordProfiler.example_counts}" +
+      @colorizer.wrap("#{example.description.strip} (FAILED - #{next_failure_index})", :failure)
+  end
+
+
+  def colorized_expanded_totals(summary)
+    if summary.failure_count > 0
+      @colorizer.wrap(expanded_totals_line(summary), RSpec.configuration.failure_color)
+    elsif summary.pending_count > 0
+      @colorizer.wrap(expanded_totals_line(summary), RSpec.configuration.pending_color)
+    else
+      @colorizer.wrap(expanded_totals_line(summary), RSpec.configuration.success_color)
+    end
+  end
+
+  def expanded_totals_line(summary)
+    summary_text = ::RSpec::Core::Formatters::Helpers.pluralize(summary.example_count, "example")
+    summary_text << ", " << ::RSpec::Core::Formatters::Helpers.pluralize(summary.failure_count, "failure")
+    summary_text << ", #{summary.pending_count} pending" if summary.pending_count > 0
+
+    [summary_text, ActiveRecordProfiler.totals_line].compact.join(", ")
+  end
+end
+
+module ActiveRecordProfiler
+  extend ActiveSupport::Concern
+
+  SKIP_QUERIES = ["SELECT tablename FROM pg_tables", "select sum(ct) from (select count(*) ct from"]
+
+  @@total_queries = 0
+  @@query_count   = 0
+  @@total_objects = 0
+
+  @@show_queries  = false
+  @@ar_queries    = []
+
+  def self.init
+    ActiveSupport::Notifications.subscribe("sql.active_record", method(:record_query))
+
+    @@total_objects = 0
+    @@total_queries = 0
+  end
+
+  def self.active_record_count
+    tables =  (ActiveRecord::Base.connection.tables - ["ar_internal_metadata", "schema_migrations"])
+    rows   = tables.map { |t| "select count(*) ct from #{t}" }.join(" union ")
+    value  = "select sum(ct) from (#{rows}) t"
+
+    response = ActiveRecord::Base.connection.execute(value)
+    response.to_a.first["sum"].to_i
+  end
+
+  def self.record_query(*_unused, data)
+    return if SKIP_QUERIES.any? { |q| data[:sql].index(q) == 0 }
+
+    @@query_count +=1
+    @@ar_queries << [data[:name], data[:sql]].compact.join(": ") if @@show_queries
+  end
+
+  def self.example_counts(suffix: " ")
+    output = "(%02d, %02d)#{suffix}" % [active_record_count, @@query_count]
+
+    @@total_objects += active_record_count
+    @@total_queries += @@query_count
+
+    # TODO is there a sane way to do this?
+    #pp @@ar_queries if @@show_queries
+    @@ar_queries = []
+    output
+  end
+
+  def self.reset_example
+    @@query_count = 0
+  end
+
+  def self.totals_line
+    "#{@@total_objects} AR objects, #{@@total_queries} AR queries"
+  end
+
+  def self.show_ar_queries
+    @@show_queries = true
+  end
+end