```ruby
require_relative '../../spec_helper'
require_relative 'fixtures/classes'

describe "Thread.list" do
  it "includes the current and main thread" do
    Thread.list.should include(Thread.current)
    Thread.list.should include(Thread.main)
  end

  it "includes threads of non-default thread groups" do
    t = Thread.new { sleep }
    begin
      ThreadGroup.new.add(t)
      Thread.list.should include(t)
    ensure
      t.kill
      t.join
    end
  end

  it "does not include deceased threads" do
    t = Thread.new { 1; }
    t.join
    Thread.list.should_not include(t)
  end

  it "includes waiting threads" do
    c = Channel.new
    t = Thread.new { c.receive }
    begin
      Thread.pass while t.status and t.status != 'sleep'
      Thread.list.should include(t)
    ensure
      c << nil
      t.join
    end
  end
end

describe "Thread.list" do
  it "needs to be reviewed for spec completeness"
end
```

Add spec for Thread.list under concurrent load
user
```ruby
require_relative '../../spec_helper'
require_relative 'fixtures/classes'

describe "Thread.list" do
  it "includes the current and main thread" do
    Thread.list.should include(Thread.current)
    Thread.list.should include(Thread.main)
  end

  it "includes threads of non-default thread groups" do
    t = Thread.new { sleep }
    begin
      ThreadGroup.new.add(t)
      Thread.list.should include(t)
    ensure
      t.kill
      t.join
    end
  end

  it "does not include deceased threads" do
    t = Thread.new { 1; }
    t.join
    Thread.list.should_not include(t)
  end

  it "includes waiting threads" do
    c = Channel.new
    t = Thread.new { c.receive }
    begin
      Thread.pass while t.status and t.status != 'sleep'
      Thread.list.should include(t)
    ensure
      c << nil
      t.join
    end
  end

  it "returns instances of Thread and not null or nil values" do
    spawner = Thread.new do
      Array.new(100) do
        Thread.new {}
      end
    end

    while spawner.alive?
      Thread.list.each { |th|
        th.should be_kind_of(Thread)
      }
    end

    threads = spawner.value
    threads.each(&:join)
  end
end
```
assistant