Enable branch coverage when coverage testing

Simplify coverage testing code while here.

Current coverage:

3311 relevant lines, 3243 lines covered and 68 lines missed. ( 97.95% )
1140 total branches, 1021 branches covered and 119 branches missed. ( 89.56% )

1 files changed, 6 insertions, 9 deletions

diff --git a/test/helper.rb b/test/helper.rb
index fe1fa594..5c310b54 100644
--- a/test/helper.rb
+++ b/test/helper.rb
@@ -1,18 +1,15 @@
 # frozen_string_literal: true
 
 if ENV.delete('COVERAGE')
-  require 'coverage'
   require 'simplecov'
 
-  def SimpleCov.rack_coverage(**opts)
-    start do
-      add_filter "/test/"
-      add_filter "/lib/rack/handler"
-      add_group('Missing'){|src| src.covered_percent < 100}
-      add_group('Covered'){|src| src.covered_percent == 100}
-    end
+  SimpleCov.start do
+    enable_coverage :branch
+    add_filter "/test/"
+    add_filter "/lib/rack/handler"
+    add_group('Missing'){|src| src.covered_percent < 100}
+    add_group('Covered'){|src| src.covered_percent == 100}
   end
-  SimpleCov.rack_coverage
 end
 
 $:.unshift(File.expand_path('../lib', __dir__))