Calculate examples count when Reporter starts

lib/turbo_tests/reporter.rb

@@ -37,6 +37,7 @@ def initialize(start_time, files, parallel_options)
     end
 
     def add(name, outputs)
+      custom_formatters = false
       outputs.each do |output|
         formatter_class =
           case name
@@ -45,11 +46,18 @@ def add(name, outputs)
           when "d", "documentation"
             RSpec::Core::Formatters::DocumentationFormatter
           else
+            custom_formatters = true
             Kernel.const_get(name)
           end
 
         @formatters << formatter_class.new(output)
       end
+
+      start if custom_formatters
+    end
+
+    def start
+      delegate_to_formatters(:start, RSpec::Core::Notifications::StartNotification.new(examples_count))
     end
 
     def group_started(notification)
@@ -123,6 +131,15 @@ def seed_notification(seed, seed_used)
 
     protected
 
+    def examples_count
+      files = ParallelTests::RSpec::Runner.send(:find_tests, @files, @parallel_options)
+      output_file = Tempfile.new("rspec-summary")
+      `#{ENV.fetch("BUNDLE_BIN_PATH")} exec rspec --dry-run --format json --out='#{output_file.path}' #{files.join(" ")}`
+
+      json_summary = JSON.parse(output_file.read, symbolize_names: true)
+      json_summary.dig(:summary, :example_count) || 0
+    end
+
     def delegate_to_formatters(method, *args)
       @formatters.each do |formatter|
         formatter.send(method, *args) if formatter.respond_to?(method)