enable branch coverage by default

Readme.md

@@ -4,15 +4,15 @@ Actionable code coverage.
  - Get actionable feedback on every successful test run
  - Only 2-5% runtime overhead on small files compared to 50% for `SimpleCov`
  - No more PRs with bad test coverage
- - Branch coverage on ruby 2.5+
+ - Branch coverage on ruby 2.5+ (disable via `branches: false`)
 
 ```Ruby
 # Gemfile
 gem 'single_cov', group: :test
 
 # spec/spec_helper.rb ... load before loading rails / minitest / libraries
 require 'single_cov'
-SingleCov.setup :rspec, branches: true
+SingleCov.setup :rspec
 
 # spec/foobar_spec.rb ... add covered! call to every test file
 require 'spec_helper'
@@ -37,7 +37,7 @@ lib/foobar.rb:23
 Call setup before loading minitest.
 
 ```Ruby
-SingleCov.setup :minitest, branches: true
+SingleCov.setup :minitest
 require 'minitest/autorun'
 ```
 

lib/single_cov.rb

@@ -2,6 +2,7 @@ module SingleCov
   COVERAGES = []
   MAX_OUTPUT = 40
   APP_FOLDERS = ["models", "serializers", "helpers", "controllers", "mailers", "views", "jobs"]
+  BRANCH_COVERAGE_SUPPORTED = (RUBY_VERSION >= "2.5.0")
 
   class << self
     # optionally rewrite the file we guessed with a lambda
@@ -66,18 +67,16 @@ def assert_tested(files: glob('{app,lib}/**/*.rb'), tests: default_tests, untest
       end
     end
 
-    def setup(framework, root: nil, branches: false)
+    def setup(framework, root: nil, branches: BRANCH_COVERAGE_SUPPORTED)
       if defined?(SimpleCov)
         raise "Load SimpleCov after SingleCov"
       end
-      if branches && RUBY_VERSION < "2.5.0"
-        warn "Branch coverage needs ruby 2.5.0"
-        @branches = false
-      else
-        @branches = branches
+      if branches && !BRANCH_COVERAGE_SUPPORTED
+        raise "Branch coverage needs ruby >= 2.5.0"
       end
 
-      @root = root if root
+      @branches = branches
+      @root = root
 
       case framework
       when :minitest

specs/single_cov_spec.rb

@@ -153,7 +153,10 @@ def self.it_does_not_complain_when_everything_is_covered
     end
 
     describe "when SimpleCov was loaded after" do
-      around { |t| change_file("test/a_test.rb", default_setup, "#{default_setup}\nrequire 'simplecov'\nSimpleCov.start\n", &t) }
+      # NOTE: SimpleCov also starts coverage and will break when we activated branches
+      let(:branchless_setup) { default_setup.sub('root: root', 'root: root, branches: false') }
+
+      around { |t| change_file("test/a_test.rb", default_setup, "#{branchless_setup}\nrequire 'simplecov'\nSimpleCov.start\n", &t) }
 
       it "works" do
         result = sh "ruby test/a_test.rb"