diff --git a/.rubocop.yml b/.rubocop.yml
index b170ace2..3eac785b 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -11,6 +11,7 @@ AllCops:
     - "vendor/bundle/**/*"
     - "vendor/bundle/**/.*"
   TargetRubyVersion: 2.5
+  NewCops: enable
   # we might wanna adopt rspec and rake but it's a bit annoying for now
   SuggestExtensions: false
 
diff --git a/lib/simplecov.rb b/lib/simplecov.rb
index 12202c9e..3c7acfce 100644
--- a/lib/simplecov.rb
+++ b/lib/simplecov.rb
@@ -11,9 +11,9 @@
   # @see https://github.com/simplecov-ruby/simplecov/issues/86
   # @see https://jira.codehaus.org/browse/JRUBY-6106
 
-  warn 'Coverage may be inaccurate; set the "--debug" command line option,' \
-    ' or do JRUBY_OPTS="--debug"' \
-    ' or set the "debug.fullTrace=true" option in your .jrubyrc'
+  warn 'Coverage may be inaccurate; set the "--debug" command line option, ' \
+       'or do JRUBY_OPTS="--debug" ' \
+       'or set the "debug.fullTrace=true" option in your .jrubyrc'
 end
 
 #
@@ -347,9 +347,9 @@ def start_coverage_measurement
     end
 
     def start_coverage_with_criteria
-      start_arguments = coverage_criteria.map do |criterion|
+      start_arguments = coverage_criteria.to_h do |criterion|
         [lookup_corresponding_ruby_coverage_name(criterion), true]
-      end.to_h
+      end
 
       start_arguments[:eval] = true if coverage_for_eval_enabled?
 
@@ -432,7 +432,7 @@ def make_parallel_tests_available
     end
 
     def probably_running_parallel_tests?
-      ENV["TEST_ENV_NUMBER"] && ENV["PARALLEL_TEST_GROUPS"]
+      ENV.fetch("TEST_ENV_NUMBER", nil) && ENV.fetch("PARALLEL_TEST_GROUPS", nil)
     end
   end
 end
diff --git a/lib/simplecov/command_guesser.rb b/lib/simplecov/command_guesser.rb
index bc949ffd..b0e2dd18 100644
--- a/lib/simplecov/command_guesser.rb
+++ b/lib/simplecov/command_guesser.rb
@@ -23,9 +23,9 @@ def from_env
         # If being run from inside parallel_tests set the command name according to the process number
         return unless ENV["PARALLEL_TEST_GROUPS"] && ENV["TEST_ENV_NUMBER"]
 
-        number = ENV["TEST_ENV_NUMBER"]
+        number = ENV.fetch("TEST_ENV_NUMBER", nil)
         number = "1" if number.empty?
-        "(#{number}/#{ENV['PARALLEL_TEST_GROUPS']})"
+        "(#{number}/#{ENV.fetch('PARALLEL_TEST_GROUPS', nil)})"
       end
 
       def from_command_line_options
diff --git a/lib/simplecov/configuration.rb b/lib/simplecov/configuration.rb
index 617e5f6e..6c2cc3d4 100644
--- a/lib/simplecov/configuration.rb
+++ b/lib/simplecov/configuration.rb
@@ -35,7 +35,7 @@ def coverage_dir(dir = nil)
       return @coverage_dir if defined?(@coverage_dir) && dir.nil?
 
       @coverage_path = nil # invalidate cache
-      @coverage_dir = (dir || "coverage")
+      @coverage_dir = dir || "coverage"
     end
 
     #
@@ -140,7 +140,7 @@ def print_error_status
     def nocov_token(nocov_token = nil)
       return @nocov_token if defined?(@nocov_token) && nocov_token.nil?
 
-      @nocov_token = (nocov_token || "nocov")
+      @nocov_token = nocov_token || "nocov"
     end
     alias skip_token nocov_token
 
@@ -344,7 +344,7 @@ def minimum_coverage_by_file(coverage = nil)
     def refuse_coverage_drop(*criteria)
       criteria = coverage_criteria if criteria.empty?
 
-      maximum_coverage_drop(criteria.map { |c| [c, 0] }.to_h)
+      maximum_coverage_drop(criteria.to_h { |c| [c, 0] })
     end
 
     #
diff --git a/lib/simplecov/defaults.rb b/lib/simplecov/defaults.rb
index 21cba877..2d82d952 100644
--- a/lib/simplecov/defaults.rb
+++ b/lib/simplecov/defaults.rb
@@ -44,7 +44,7 @@
       load filename
     rescue LoadError, StandardError
       warn "Warning: Error occurred while trying to load #{filename}. " \
-        "Error message: #{$!.message}"
+           "Error message: #{$!.message}"
     end
     break
   end
diff --git a/lib/simplecov/formatter/simple_formatter.rb b/lib/simplecov/formatter/simple_formatter.rb
index 5f66af24..b99338c0 100644
--- a/lib/simplecov/formatter/simple_formatter.rb
+++ b/lib/simplecov/formatter/simple_formatter.rb
@@ -11,7 +11,7 @@ def format(result)
         output = +""
         result.groups.each do |name, files|
           output << "Group: #{name}\n"
-          output << "=" * 40
+          output << ("=" * 40)
           output << "\n"
           files.each do |file|
             output << "#{file.filename} (coverage: #{file.covered_percent.round(2)}%)\n"
diff --git a/lib/simplecov/load_global_config.rb b/lib/simplecov/load_global_config.rb
index 64dc62ae..758bbcfc 100644
--- a/lib/simplecov/load_global_config.rb
+++ b/lib/simplecov/load_global_config.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 require "etc"
-home_dir = (ENV["HOME"] && File.expand_path("~")) || Etc.getpwuid.dir || (ENV["USER"] && File.expand_path("~#{ENV['USER']}"))
+home_dir = (Dir.home && File.expand_path("~")) || Etc.getpwuid.dir || (ENV.fetch("USER", nil) && File.expand_path("~#{ENV.fetch('USER', nil)}"))
 if home_dir
   global_config_path = File.join(home_dir, ".simplecov")
   load global_config_path if File.exist?(global_config_path)
diff --git a/lib/simplecov/result.rb b/lib/simplecov/result.rb
index 51726f1a..7741678c 100644
--- a/lib/simplecov/result.rb
+++ b/lib/simplecov/result.rb
@@ -83,7 +83,7 @@ def self.from_hash(hash)
 
     def coverage
       keys = original_result.keys & filenames
-      Hash[keys.zip(original_result.values_at(*keys))]
+      keys.zip(original_result.values_at(*keys)).to_h
     end
 
     # Applies all configured SimpleCov filters on this result's source files
diff --git a/lib/simplecov/source_file/line.rb b/lib/simplecov/source_file/line.rb
index 7aab40c2..2491e586 100644
--- a/lib/simplecov/source_file/line.rb
+++ b/lib/simplecov/source_file/line.rb
@@ -65,7 +65,8 @@ def status
         return "skipped" if skipped?
         return "never" if never?
         return "missed" if missed?
-        return "covered" if covered?
+
+        "covered" if covered?
       end
     end
   end
diff --git a/simplecov.gemspec b/simplecov.gemspec
index c770c14d..21f35eeb 100644
--- a/simplecov.gemspec
+++ b/simplecov.gemspec
@@ -29,7 +29,8 @@ Gem::Specification.new do |gem|
     "changelog_uri"     => "https://github.com/simplecov-ruby/simplecov/blob/main/CHANGELOG.md",
     "documentation_uri" => "https://www.rubydoc.info/gems/simplecov/#{gem.version}",
     "mailing_list_uri"  => "https://groups.google.com/forum/#!forum/simplecov",
-    "source_code_uri"   => "https://github.com/simplecov-ruby/simplecov/tree/v#{gem.version}"
+    "source_code_uri"   => "https://github.com/simplecov-ruby/simplecov/tree/v#{gem.version}",
+"rubygems_mfa_required" => "true"
   }
 
   gem.required_ruby_version = ">= 2.5.0"
diff --git a/spec/filters_spec.rb b/spec/filters_spec.rb
index 82028303..fa25d12f 100644
--- a/spec/filters_spec.rb
+++ b/spec/filters_spec.rb
@@ -36,15 +36,15 @@
     expect(SimpleCov::StringFilter.new(parent_dir_name)).not_to be_matches subject
   end
 
-  it "matches a new SimpleCov::RegexFilter /\/fixtures\//" do
+  it "matches a new SimpleCov::RegexFilter //fixtures//" do
     expect(SimpleCov::RegexFilter.new(/\/fixtures\//)).to be_matches subject
   end
 
-  it "doesn't match a new SimpleCov::RegexFilter /^\/fixtures\//" do
+  it "doesn't match a new SimpleCov::RegexFilter /^/fixtures//" do
     expect(SimpleCov::RegexFilter.new(/^\/fixtures\//)).not_to be_matches subject
   end
 
-  it "matches a new SimpleCov::RegexFilter /^\/spec\//" do
+  it "matches a new SimpleCov::RegexFilter /^/spec//" do
     expect(SimpleCov::RegexFilter.new(/^\/spec\//)).to be_matches subject
   end
 
diff --git a/spec/last_run_spec.rb b/spec/last_run_spec.rb
index a1543067..b6d7d295 100644
--- a/spec/last_run_spec.rb
+++ b/spec/last_run_spec.rb
@@ -18,7 +18,7 @@
 
   context "reading" do
     context "but the last_run file does not exist" do
-      before { File.delete(subject.last_run_path) if File.exist?(subject.last_run_path) }
+      before { FileUtils.rm_f(subject.last_run_path) }
 
       it "returns nil" do
         expect(subject.read).to be_nil
diff --git a/spec/result_merger_spec.rb b/spec/result_merger_spec.rb
index 0bbb70f0..d9544e42 100644
--- a/spec/result_merger_spec.rb
+++ b/spec/result_merger_spec.rb
@@ -6,7 +6,7 @@
 
 describe SimpleCov::ResultMerger do
   after do
-    File.delete(SimpleCov::ResultMerger.resultset_path) if File.exist?(SimpleCov::ResultMerger.resultset_path)
+    FileUtils.rm_f(SimpleCov::ResultMerger.resultset_path)
   end
 
   let(:resultset1) do
diff --git a/spec/support/fail_rspec_on_ruby_warning.rb b/spec/support/fail_rspec_on_ruby_warning.rb
index b5115161..5d99c2b2 100644
--- a/spec/support/fail_rspec_on_ruby_warning.rb
+++ b/spec/support/fail_rspec_on_ruby_warning.rb
@@ -54,9 +54,7 @@ def write_other_warnings_to_tmp(other_warnings)
     output_dir = File.join(@app_root, "tmp")
     FileUtils.mkdir_p(output_dir)
     output_file = File.join(output_dir, "warnings.txt")
-    File.open(output_file, "w") do |file|
-      file.write(other_warnings.join("\n") << "\n")
-    end
+    File.write(output_file, other_warnings.join("\n") << "\n")
     puts
     puts "Non-app warnings written to tmp/warnings.txt"
     puts