Fix ThreadSafety::NewThread cop

lib/rubocop/cop/thread_safety/new_thread.rb

@@ -12,17 +12,15 @@ module ThreadSafety
       #   Thread.new { do_work }
       class NewThread < Base
         MSG = 'Avoid starting new threads.'
-        RESTRICT_ON_SEND = %i[new].freeze
+        RESTRICT_ON_SEND = %i[new fork start].freeze
 
         # @!method new_thread?(node)
         def_node_matcher :new_thread?, <<~MATCHER
-          (send (const {nil? cbase} :Thread) :new)
+          (send (const {nil? cbase} :Thread) {:new :fork :start} ...)
         MATCHER
 
         def on_send(node)
-          return unless new_thread?(node)
-
-          add_offense(node)
+          new_thread?(node) { add_offense(node) }
         end
       end
     end

spec/rubocop/cop/thread_safety/new_thread_spec.rb

@@ -1,17 +1,47 @@
 # frozen_string_literal: true
 
 RSpec.describe RuboCop::Cop::ThreadSafety::NewThread, :config do
+  let(:msg) { 'Avoid starting new threads.' }
+
   it 'registers an offense for starting a new thread' do
     expect_offense(<<~RUBY)
       Thread.new { do_work }
-      ^^^^^^^^^^ Avoid starting new threads.
+      ^^^^^^^^^^ #{msg}
+    RUBY
+  end
+
+  it 'registers an offense for starting a new thread with positional arguments' do
+    expect_offense(<<~RUBY)
+      Thread.new(1) { do_work }
+      ^^^^^^^^^^^^^ #{msg}
+    RUBY
+  end
+
+  it 'registers an offense for starting a new thread with keyword arguments' do
+    expect_offense(<<~RUBY)
+      Thread.new(a: 42) { do_work }
+      ^^^^^^^^^^^^^^^^^ #{msg}
+    RUBY
+  end
+
+  it 'registers an offense for starting a new thread with `fork` method' do
+    expect_offense(<<~RUBY)
+      Thread.fork { do_work }
+      ^^^^^^^^^^^ #{msg}
+    RUBY
+  end
+
+  it 'registers an offense for starting a new thread with `start` method' do
+    expect_offense(<<~RUBY)
+      Thread.start { do_work }
+      ^^^^^^^^^^^^ #{msg}
     RUBY
   end
 
   it 'registers an offense for starting a new thread with top-level constant' do
     expect_offense(<<~RUBY)
       ::Thread.new { do_work }
-      ^^^^^^^^^^^^ Avoid starting new threads.
+      ^^^^^^^^^^^^ #{msg}
     RUBY
   end