diff --git a/Gemfile b/Gemfile
index 44f6e48b80..24fbed33cd 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,6 +9,7 @@ gem "nio4r", "~> 2.0"
 gem "rack", "< 3.0"
 gem "minitest", "~> 5.11"
 gem "minitest-retry"
+gem "minitest-proveit"
 
 gem "jruby-openssl", :platform => "jruby"
 
diff --git a/History.md b/History.md
index 2a9416fc57..f2da4d47ee 100644
--- a/History.md
+++ b/History.md
@@ -1,12 +1,16 @@
 ## Master
 
-x features
+* Features
+  * Add log_formatter configuration #1816
+
+* Bugfixes
+  * Your bugfix goes here (#Github Number)
+
+## 4.0.1 / 2019-07-11
 
 * 2 bugfixes
-  * Socket removed after reload (#1829)
-  * Add extconf tests for DTLS_method & TLS_server_method, use in minissl.rb.  (#1832)
-* 1 feature
-  * Add log_formatter configuration
+  * Fix socket removed after reload - should fix problems with systemd socket activation. (#1829)
+  * Add extconf tests for DTLS_method & TLS_server_method, use in minissl.rb. Should fix "undefined symbol: DTLS_method" when compiling against old OpenSSL versions. (#1832)
 
 
 ## 4.0.0 / 2019-06-25
@@ -1439,3 +1443,12 @@ be added back in a future date when a java Puma::MiniSSL is added.
 ## 1.0.0 / 2012-03-29
 
 * Released!
+
+## Ignore - this is for maintainers to copy-paste during release
+## Master
+
+* Features
+  * Your feature goes here (#Github Number)
+
+* Bugfixes
+  * Your bugfix goes here (#Github Number)
diff --git a/README.md b/README.md
index 3bd0c5e6b8..ac75ef1143 100644
--- a/README.md
+++ b/README.md
@@ -10,36 +10,38 @@
 [![Code Climate](https://codeclimate.com/github/puma/puma.svg)](https://codeclimate.com/github/puma/puma)
 [![SemVer](https://api.dependabot.com/badges/compatibility_score?dependency-name=puma&package-manager=bundler&version-scheme=semver)](https://dependabot.com/compatibility-score.html?dependency-name=puma&package-manager=bundler&version-scheme=semver)
 
-Puma is a **simple, fast, threaded, and highly concurrent HTTP 1.1 server for Ruby/Rack applications** in development and production.
+Puma is a **simple, fast, multi-threaded, and highly concurrent HTTP 1.1 server for Ruby/Rack applications**.
 
 ## Built For Speed &amp; Concurrency
 
-Under the hood, Puma processes requests using a C-optimized Ragel extension (inherited from Mongrel) that provides fast, accurate HTTP 1.1 protocol parsing in a portable way. Puma then serves the request in a thread from an internal thread pool. Since each request is served in a separate thread, truly concurrent Ruby implementations (JRuby, Rubinius) will use all available CPU cores.
+Puma processes requests using a C-optimized Ragel extension (inherited from Mongrel) that provides fast, accurate HTTP 1.1 protocol parsing in a portable way. Puma then serves the request using a thread pool. Each request is served in a separate thread, so truly concurrent Ruby implementations (JRuby, Rubinius) will use all available CPU cores.
 
 Puma was designed to be the go-to server for [Rubinius](https://rubini.us), but also works well with JRuby and MRI.
 
-On MRI, there is a Global VM Lock (GVL) that ensures only one thread can run Ruby code at a time. But if you're doing a lot of blocking IO (such as HTTP calls to external APIs like Twitter), Puma still improves MRI's throughput by allowing blocking IO to be run concurrently.
+On MRI, there is a Global VM Lock (GVL) that ensures only one thread can run Ruby code at a time. But if you're doing a lot of blocking IO (such as HTTP calls to external APIs like Twitter), Puma still improves MRI's throughput by allowing IO waiting to be done in parallel.
 
 ## Quick Start
 
 ```
 $ gem install puma
-$ puma <any rackup (*.ru) file>
+$ puma
 ```
 
+Without arguments, puma will look for a rackup (.ru) file in the current working directory called `config.ru`.
+
 ## Frameworks
 
 ### Rails
 
-Puma is the default server for Rails, and should already be included in your Gemfile.
+Puma is the default server for Rails, included in the generated Gemfile.
 
-Then start your server with the `rails` command:
+Start your server with the `rails` command:
 
 ```
-$ rails s
+$ rails server
 ```
 
-Many configuration options are not available when using `rails s`. It is recommended that you use Puma's executable instead:
+Many configuration options and Puma features are not available when using `rails server`. It is recommended that you use Puma's executable instead:
 
 ```
 $ bundle exec puma
@@ -53,7 +55,7 @@ You can run your Sinatra application with Puma from the command line like this:
 $ ruby app.rb -s Puma
 ```
 
-Or you can configure your application to always use Puma:
+Or you can configure your Sinatra application to always use Puma:
 
 ```ruby
 require 'sinatra'
@@ -72,9 +74,9 @@ Puma uses a thread pool. You can set the minimum and maximum number of threads t
 $ puma -t 8:32
 ```
 
-Puma will automatically scale the number of threads, from the minimum until it caps out at the maximum, based on how much traffic is present. The current default is `0:16`. Feel free to experiment, but be careful not to set the number of maximum threads to a large number, as you may exhaust resources on the system (or hit resource limits).
+Puma will automatically scale the number of threads, from the minimum until it caps out at the maximum, based on how much traffic is present. The current default is `0:16`. Feel free to experiment, but be careful not to set the number of maximum threads to a large number, as you may exhaust resources on the system (or cause contention for the Global VM Lock, when using MRI).
 
-Be aware that additionally Puma creates threads on its own for internal purposes (e.g. handling slow clients). So even if you specify -t 1:1, expect around 7 threads created in your application.
+Be aware that additionally Puma creates threads on its own for internal purposes (e.g. handling slow clients). So, even if you specify -t 1:1, expect around 7 threads created in your application.
 
 ### Clustered mode
 
@@ -84,9 +86,9 @@ Puma also offers "clustered mode". Clustered mode `fork`s workers from a master
 $ puma -t 8:32 -w 3
 ```
 
-Note that threads are still used in clustered mode, and the `-t` thread flag setting is per worker, so `-w 2 -t 16:16` will spawn 32 threads in total.
+Note that threads are still used in clustered mode, and the `-t` thread flag setting is per worker, so `-w 2 -t 16:16` will spawn 32 threads in total, with 16 in each worker process.
 
-In clustered mode, Puma may "preload" your application. This loads all the application code *prior* to forking. Preloading reduces total memory usage of your application via an operating system feature called [copy-on-write](https://en.wikipedia.org/wiki/Copy-on-write) (Ruby 2.0+ only). Use the `--preload` flag from the command line:
+In clustered mode, Puma can "preload" your application. This loads all the application code *prior* to forking. Preloading reduces total memory usage of your application via an operating system feature called [copy-on-write](https://en.wikipedia.org/wiki/Copy-on-write) (Ruby 2.0+ only). Use the `--preload` flag from the command line:
 
 ```
 $ puma -w 3 --preload
@@ -111,8 +113,7 @@ end
 
 This code can be used to setup the process before booting the application, allowing
 you to do some Puma-specific things that you don't want to embed in your application.
-For instance, you could fire a log notification that a worker booted or send something to statsd.
-This can be called multiple times.
+For instance, you could fire a log notification that a worker booted or send something to statsd. This can be called multiple times.
 
 If you're preloading your application and using ActiveRecord, it's recommended that you setup your connection pool here:
 
@@ -125,7 +126,7 @@ on_worker_boot do
 end
 ```
 
-On top of that, you can specify a block in your configuration file that will be run before workers are forked:
+`before_fork` specifies a block to be run before workers are forked:
 
 ```ruby
 # config/puma.rb
@@ -138,13 +139,13 @@ Preloading can’t be used with phased restart, since phased restart kills and r
 
 ### Binding TCP / Sockets
 
-In contrast to many other server configs which require multiple flags, Puma simply uses one URI parameter with the `-b` (or `--bind`) flag:
+Bind Puma to a socket with the `-b` (or `--bind`) flag:
 
 ```
 $ puma -b tcp://127.0.0.1:9292
 ```
 
-Want to use UNIX Sockets instead of TCP (which can provide a 5-10% performance boost)?
+To use a UNIX Socket instead of TCP:
 
 ```
 $ puma -b unix:///var/run/puma.sock
@@ -157,13 +158,14 @@ $ puma -b 'unix:///var/run/puma.sock?umask=0111'
 ```
 
 Need a bit of security? Use SSL sockets:
+
 ```
 $ puma -b 'ssl://127.0.0.1:9292?key=path_to_key&cert=path_to_cert'
 ```
 
 #### Controlling SSL Cipher Suites
 
-Need to use or avoid specific SSL cipher suites? Use `ssl_cipher_filter` or `ssl_cipher_list` options.
+To use or avoid specific SSL cipher suites, use `ssl_cipher_filter` or `ssl_cipher_list` options.
 
 ##### Ruby:
 
@@ -179,7 +181,7 @@ $ puma -b 'ssl://127.0.0.1:9292?keystore=path_to_keystore&keystore-pass=keystore
 
 See https://www.openssl.org/docs/man1.0.2/apps/ciphers.html for cipher filter format and full list of cipher suites.
 
-Don't want to use insecure TLSv1.0 ?
+Disable TLS v1 with the `no_tlsv1` option:
 
 ```
 $ puma -b 'ssl://127.0.0.1:9292?key=path_to_key&cert=path_to_cert&no_tlsv1=true'
@@ -187,13 +189,13 @@ $ puma -b 'ssl://127.0.0.1:9292?key=path_to_key&cert=path_to_cert&no_tlsv1=true'
 
 ### Control/Status Server
 
-Puma has a built-in status/control app that can be used to query and control Puma itself.
+Puma has a built-in status and control app that can be used to query and control Puma.
 
 ```
 $ puma --control-url tcp://127.0.0.1:9293 --control-token foo
 ```
 
-Puma will start the control server on localhost port 9293. All requests to the control server will need to include `token=foo` as a query parameter. This allows for simple authentication. Check out [status.rb](https://github.com/puma/puma/blob/master/lib/puma/app/status.rb) to see what the app has available.
+Puma will start the control server on localhost port 9293. All requests to the control server will need to include control token (in this case, `token=foo`) as a query parameter. This allows for simple authentication. Check out [status.rb](https://github.com/puma/puma/blob/master/lib/puma/app/status.rb) to see what the status app has available.
 
 You can also interact with the control server via `pumactl`. This command will restart Puma:
 
@@ -205,13 +207,13 @@ To see a list of `pumactl` options, use `pumactl --help`.
 
 ### Configuration File
 
-You can also provide a configuration file which Puma will use with the `-C` (or `--config`) flag:
+You can also provide a configuration file with the `-C` (or `--config`) flag:
 
 ```
 $ puma -C /path/to/config
 ```
 
-If no configuration file is specified, Puma will look for a configuration file at `config/puma.rb`. If an environment is specified, either via the `-e` and `--environment` flags, or through the `RACK_ENV` environment variable, the default file location will be `config/puma/environment_name.rb`.
+If no configuration file is specified, Puma will look for a configuration file at `config/puma.rb`. If an environment is specified, either via the `-e` and `--environment` flags, or through the `RACK_ENV` environment variable, Puma looks for configuration at `config/puma/<environment_name>.rb`.
 
 If you want to prevent Puma from looking for a configuration file in those locations, provide a dash as the argument to the `-C` (or `--config`) flag:
 
@@ -236,7 +238,7 @@ Puma responds to several signals. A detailed guide to using UNIX signals with Pu
 Some platforms do not support all Puma features.
 
   * **JRuby**, **Windows**: server sockets are not seamless on restart, they must be closed and reopened. These platforms have no way to pass descriptors into a new process that is exposed to Ruby. Also, cluster mode is not supported due to a lack of fork(2).
-  * **Windows**: daemon mode is not supported due to a lack of fork(2).
+  * **Windows**: Cluster mode is not supported due to a lack of fork(2).
 
 ## Known Bugs
 
@@ -278,6 +280,24 @@ $ bundle install
 $ bundle exec rake
 ```
 
+To run a single test file, use the `TEST` environment variable:
+
+```bash
+$ TEST=test/test_binder.rb bundle exec rake test
+```
+
+Or use [`m`](https://github.com/qrush/m):
+
+```
+$ bundle exec m test/test_binder.rb
+```
+
+Which can also be used to run a single test case:
+
+```
+$ bundle exec m test/test_binder.rb:37
+```
+
 ## License
 
 Puma is copyright Evan Phoenix and contributors, licensed under the BSD 3-Clause license. See the included LICENSE file for details.
diff --git a/Rakefile b/Rakefile
index f56dce4a4f..231be50b12 100644
--- a/Rakefile
+++ b/Rakefile
@@ -7,14 +7,12 @@ require_relative 'lib/puma/detect'
 require 'rubygems/package_task'
 require 'bundler/gem_tasks'
 
-gemspec = Gem::Specification.load(Dir['*.gemspec'].first)
+gemspec = Gem::Specification.load("puma.gemspec")
 Gem::PackageTask.new(gemspec).define
 
 # Add rubocop task
 RuboCop::RakeTask.new
 
-spec = Gem::Specification.load("puma.gemspec")
-
 # generate extension code using Ragel (C and Java)
 desc "Generate extension code (C and Java) using Ragel"
 task :ragel
@@ -40,16 +38,16 @@ task :ragel => ['ext/puma_http11/org/jruby/puma/Http11Parser.java']
 if !Puma.jruby?
   # compile extensions using rake-compiler
   # C (MRI, Rubinius)
-  Rake::ExtensionTask.new("puma_http11", spec) do |ext|
+  Rake::ExtensionTask.new("puma_http11", gemspec) do |ext|
     # place extension inside namespace
     ext.lib_dir = "lib/puma"
 
-      CLEAN.include "lib/puma/{1.8,1.9}"
-      CLEAN.include "lib/puma/puma_http11.rb"
-    end
+    CLEAN.include "lib/puma/{1.8,1.9}"
+    CLEAN.include "lib/puma/puma_http11.rb"
+  end
 else
   # Java (JRuby)
-  Rake::JavaExtensionTask.new("puma_http11", spec) do |ext|
+  Rake::JavaExtensionTask.new("puma_http11", gemspec) do |ext|
     ext.lib_dir = "lib/puma"
   end
 end
@@ -75,6 +73,7 @@ end
 
 namespace :test do
   desc "Run the integration tests"
+  
   task :integration do
     sh "ruby test/shell/run.rb"
   end
diff --git a/lib/puma.rb b/lib/puma.rb
index 7a65d1256f..c48e352fdf 100644
--- a/lib/puma.rb
+++ b/lib/puma.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Standard libraries
 require 'socket'
 require 'tempfile'
diff --git a/lib/puma/accept_nonblock.rb b/lib/puma/accept_nonblock.rb
index a8d67673f2..e697032a2e 100644
--- a/lib/puma/accept_nonblock.rb
+++ b/lib/puma/accept_nonblock.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'openssl'
 
 module OpenSSL
diff --git a/lib/puma/app/status.rb b/lib/puma/app/status.rb
index 58615d7db1..84b3965415 100644
--- a/lib/puma/app/status.rb
+++ b/lib/puma/app/status.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'json'
 
 module Puma
diff --git a/lib/puma/configuration.rb b/lib/puma/configuration.rb
index 900a0105ee..6034520a1f 100644
--- a/lib/puma/configuration.rb
+++ b/lib/puma/configuration.rb
@@ -20,7 +20,7 @@ module ConfigDefault
   # In this class any "user" specified options take precedence over any
   # "file" specified options, take precedence over any "default" options.
   #
-  # User input is prefered over "defaults":
+  # User input is preferred over "defaults":
   #   user_options    = { foo: "bar" }
   #   default_options = { foo: "zoo" }
   #   options = UserFileDefaultOptions.new(user_options, default_options)
@@ -32,7 +32,7 @@ module ConfigDefault
   #   puts options.all_of(:foo)
   #   # => ["bar", "zoo"]
   #
-  # A "file" option can be set. This config will be prefered over "default" options
+  # A "file" option can be set. This config will be preferred over "default" options
   # but will defer to any available "user" specified options.
   #
   #   user_options    = { foo: "bar" }
diff --git a/lib/puma/const.rb b/lib/puma/const.rb
index 15b9b7e169..77e86d44c1 100644
--- a/lib/puma/const.rb
+++ b/lib/puma/const.rb
@@ -100,7 +100,7 @@ class UnsupportedOption < RuntimeError
   # too taxing on performance.
   module Const
 
-    PUMA_VERSION = VERSION = "4.0.0".freeze
+    PUMA_VERSION = VERSION = "4.0.1".freeze
     CODE_NAME = "4 Fast 4 Furious".freeze
     PUMA_SERVER_STRING = ['puma', PUMA_VERSION, CODE_NAME].join(' ').freeze
 
@@ -160,6 +160,9 @@ module Const
     LINE_END = "\r\n".freeze
     REMOTE_ADDR = "REMOTE_ADDR".freeze
     HTTP_X_FORWARDED_FOR = "HTTP_X_FORWARDED_FOR".freeze
+    HTTP_X_FORWARDED_SSL = "HTTP_X_FORWARDED_SSL".freeze
+    HTTP_X_FORWARDED_SCHEME = "HTTP_X_FORWARDED_SCHEME".freeze
+    HTTP_X_FORWARDED_PROTO = "HTTP_X_FORWARDED_PROTO".freeze
 
     SERVER_NAME = "SERVER_NAME".freeze
     SERVER_PORT = "SERVER_PORT".freeze
diff --git a/lib/puma/dsl.rb b/lib/puma/dsl.rb
index f5ab4ae519..a6ac191a5e 100644
--- a/lib/puma/dsl.rb
+++ b/lib/puma/dsl.rb
@@ -480,7 +480,7 @@ def worker_timeout(timeout)
         raise "The minimum worker_timeout must be greater than the worker reporting interval (#{min})"
       end
 
-      @options[:worker_timeout] = Integer(timeout)
+      @options[:worker_timeout] = timeout
     end
 
     # *Cluster mode only* Set the timeout for workers to boot
diff --git a/lib/puma/events.rb b/lib/puma/events.rb
index 04308e2fa2..148926cb95 100644
--- a/lib/puma/events.rb
+++ b/lib/puma/events.rb
@@ -39,8 +39,8 @@ def call(str)
     #
     def initialize(stdout, stderr)
       @formatter = DefaultFormatter.new
-      @stdout = stdout
-      @stderr = stderr
+      @stdout = stdout.dup
+      @stderr = stderr.dup
 
       @stdout.sync = true
       @stderr.sync = true
@@ -103,7 +103,10 @@ def format(str)
     # parsing exception.
     #
     def parse_error(server, env, error)
-      @stderr.puts "#{Time.now}: HTTP parse error, malformed request (#{env[HTTP_X_FORWARDED_FOR] || env[REMOTE_ADDR]}): #{error.inspect}\n---\n"
+      @stderr.puts "#{Time.now}: HTTP parse error, malformed request " \
+        "(#{env[HTTP_X_FORWARDED_FOR] || env[REMOTE_ADDR]}#{env[REQUEST_PATH]}): " \
+        "#{error.inspect}" \
+        "\n---\n"
     end
 
     # An SSL error has occurred.
diff --git a/lib/puma/plugin/tmp_restart.rb b/lib/puma/plugin/tmp_restart.rb
index 7c2c402abd..5e326bf3a2 100644
--- a/lib/puma/plugin/tmp_restart.rb
+++ b/lib/puma/plugin/tmp_restart.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'puma/plugin'
 
 Puma::Plugin.create do
diff --git a/lib/puma/rack/builder.rb b/lib/puma/rack/builder.rb
index c9eb29d2db..74c8aa40c2 100644
--- a/lib/puma/rack/builder.rb
+++ b/lib/puma/rack/builder.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Puma
 end
 
diff --git a/lib/puma/rack/urlmap.rb b/lib/puma/rack/urlmap.rb
index adaf74a1e3..0d0a5144f1 100644
--- a/lib/puma/rack/urlmap.rb
+++ b/lib/puma/rack/urlmap.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Puma::Rack
   # Rack::URLMap takes a hash mapping urls or paths to apps, and
   # dispatches accordingly.  Support for HTTP/1.1 host names exists if
diff --git a/lib/puma/rack_default.rb b/lib/puma/rack_default.rb
index f95fd97289..016f54d424 100644
--- a/lib/puma/rack_default.rb
+++ b/lib/puma/rack_default.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rack/handler/puma'
 
 module Rack::Handler
diff --git a/lib/puma/reactor.rb b/lib/puma/reactor.rb
index 0d419cfd0c..5bf10f2c19 100644
--- a/lib/puma/reactor.rb
+++ b/lib/puma/reactor.rb
@@ -23,7 +23,7 @@ module Puma
   # A connection comes into a `Puma::Server` instance, it is then passed to a `Puma::Reactor` instance,
   # which stores it in an array and waits for any of the connections to be ready for reading.
   #
-  # The waiting/wake up is performed with nio4r, which will use the apropriate backend (libev, Java NIO or
+  # The waiting/wake up is performed with nio4r, which will use the appropriate backend (libev, Java NIO or
   # just plain IO#select). The call to `NIO::Selector#select` will "wake up" and
   # return the references to any objects that caused it to "wake". The reactor
   # then loops through each of these request objects, and sees if they're complete. If they
diff --git a/lib/puma/server.rb b/lib/puma/server.rb
index ac1e28674a..d4435f264e 100644
--- a/lib/puma/server.rb
+++ b/lib/puma/server.rb
@@ -588,8 +588,11 @@ def normalize_env(env, client)
     end
 
     def default_server_port(env)
-      return PORT_443 if env[HTTPS_KEY] == 'on' || env[HTTPS_KEY] == 'https'
-      env['HTTP_X_FORWARDED_PROTO'] == 'https' ? PORT_443 : PORT_80
+      if ['on', HTTPS].include?(env[HTTPS_KEY]) || env[HTTP_X_FORWARDED_PROTO].to_s[0...5] == HTTPS || env[HTTP_X_FORWARDED_SCHEME] == HTTPS || env[HTTP_X_FORWARDED_SSL] == "on"
+        PORT_443
+      else
+        PORT_80
+      end
     end
 
     # Takes the request +req+, invokes the Rack application to construct
@@ -627,7 +630,7 @@ def handle_request(req, lines)
       head = env[REQUEST_METHOD] == HEAD
 
       env[RACK_INPUT] = body
-      env[RACK_URL_SCHEME] =  env[HTTPS_KEY] ? HTTPS : HTTP
+      env[RACK_URL_SCHEME] = default_server_port(env) == PORT_443 ? HTTPS : HTTP
 
       if @early_hints
         env[EARLY_HINTS] = lambda { |headers|
diff --git a/lib/rack/handler/puma.rb b/lib/rack/handler/puma.rb
index 4607b7c103..a8f03bc794 100644
--- a/lib/rack/handler/puma.rb
+++ b/lib/rack/handler/puma.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rack/handler'
 
 module Rack
diff --git a/test/helper.rb b/test/helper.rb
index 85b255d596..8ada8f5a39 100644
--- a/test/helper.rb
+++ b/test/helper.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 # Copyright (c) 2011 Evan Phoenix
 # Copyright (c) 2005 Zed A. Shaw
 
@@ -5,21 +6,16 @@
   begin
     require 'stopgap_13632'
   rescue LoadError
+    puts "For test stability, you must install the stopgap_13632 gem."
+    exit(1)
   end
 end
 
-begin
-  require "bundler/setup"
-  # bundler/setup may not load bundler
-  require "bundler" unless Bundler.const_defined?(:ORIGINAL_ENV)
-rescue LoadError
-  warn "Failed to load bundler ... this should only happen during package building"
-end
-
 require "net/http"
 require "timeout"
 require "minitest/autorun"
 require "minitest/pride"
+require "minitest/proveit"
 
 $LOAD_PATH << File.expand_path("../../lib", __FILE__)
 Thread.abort_on_exception = true
@@ -126,3 +122,10 @@ def next_port(incr = 1)
 end
 
 Minitest::Test.include TestSkips
+
+class Minitest::Test
+  def self.run(reporter, options = {}) # :nodoc:
+    prove_it!
+    super
+  end
+end
diff --git a/test/test_app_status.rb b/test/test_app_status.rb
index 7697975633..2dd1519d86 100644
--- a/test/test_app_status.rb
+++ b/test/test_app_status.rb
@@ -1,9 +1,13 @@
+# frozen_string_literal: true
+
 require_relative "helper"
 
 require "puma/app/status"
 require "rack"
 
 class TestAppStatus < Minitest::Test
+  parallelize_me!
+
   class FakeServer
     def initialize
       @status = :running
diff --git a/test/test_binder.rb b/test/test_binder.rb
index db9f659c2b..3146031e03 100644
--- a/test/test_binder.rb
+++ b/test/test_binder.rb
@@ -1,96 +1,85 @@
+# frozen_string_literal: true
+
 require_relative "helper"
 
 require "puma/binder"
 require "puma/puma_http11"
 
-class TestBinder < Minitest::Test
+class TestBinderBase < Minitest::Test
   def setup
     @events = Puma::Events.null
     @binder = Puma::Binder.new(@events)
+    @key    = File.expand_path "../../examples/puma/puma_keypair.pem", __FILE__
+    @cert   = File.expand_path "../../examples/puma/cert_puma.pem", __FILE__
   end
 
-  def test_localhost_addresses_dont_alter_listeners_for_tcp_addresses
-    skip_on :jruby
+  private
+
+  def ssl_context_for_binder(binder)
+    binder.instance_variable_get(:@ios)[0].instance_variable_get(:@ctx)
+  end
+end
 
+class TestBinder < TestBinderBase
+  def test_localhost_addresses_dont_alter_listeners_for_tcp_addresses
     @binder.parse(["tcp://localhost:10001"], @events)
 
     assert_equal [], @binder.listeners
   end
+end
 
-  def test_localhost_addresses_dont_alter_listeners_for_ssl_addresses
-    skip_on :jruby
+class TestBinderJRuby < TestBinderBase
+  def setup
+    super
+    skip_unless :jruby
+  end
 
-    key =  File.expand_path "../../examples/puma/puma_keypair.pem", __FILE__
-    cert = File.expand_path "../../examples/puma/cert_puma.pem", __FILE__
+  def test_binder_parses_jruby_ssl_options
+    keystore = File.expand_path "../../examples/puma/keystore.jks", __FILE__
+    ssl_cipher_list = "TLS_DHE_RSA_WITH_DES_CBC_SHA,TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA"
 
-    @binder.parse(["ssl://localhost:10002?key=#{key}&cert=#{cert}"], @events)
+    @binder.parse(["ssl://0.0.0.0:8080?keystore=#{keystore}&keystore-pass=&ssl_cipher_list=#{ssl_cipher_list}"], @events)
 
-    assert_equal [], @binder.listeners
+    assert_equal keystore, ssl_context_for_binder(@binder).keystore
+    assert_equal ssl_cipher_list, ssl_context_for_binder(@binder).ssl_cipher_list
   end
+end
 
-  def test_binder_parses_ssl_cipher_filter
+class TestBinderMRI < TestBinderBase
+  def setup
+    super
     skip_on :jruby
+  end
 
-    key =  File.expand_path "../../examples/puma/puma_keypair.pem", __FILE__
-    cert = File.expand_path "../../examples/puma/cert_puma.pem", __FILE__
-    ssl_cipher_filter = "AES@STRENGTH"
-
-    @binder.parse(["ssl://0.0.0.0?key=#{key}&cert=#{cert}&ssl_cipher_filter=#{ssl_cipher_filter}"], @events)
+  def test_localhost_addresses_dont_alter_listeners_for_ssl_addresses
+    @binder.parse(["ssl://localhost:10002?key=#{@key}&cert=#{@cert}"], @events)
 
-    ssl = @binder.instance_variable_get(:@ios)[0]
-    ctx = ssl.instance_variable_get(:@ctx)
-    assert_equal(ssl_cipher_filter, ctx.ssl_cipher_filter)
+    assert_equal [], @binder.listeners
   end
 
-  def test_binder_parses_jruby_ssl_options
-    skip_unless :jruby
+  def test_binder_parses_ssl_cipher_filter
+    ssl_cipher_filter = "AES@STRENGTH"
 
-    keystore = File.expand_path "../../examples/puma/keystore.jks", __FILE__
-    ssl_cipher_list = "TLS_DHE_RSA_WITH_DES_CBC_SHA,TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA"
-    @binder.parse(["ssl://0.0.0.0:8080?keystore=#{keystore}&keystore-pass=&ssl_cipher_list=#{ssl_cipher_list}"], @events)
+    @binder.parse(["ssl://0.0.0.0?key=#{@key}&cert=#{@cert}&ssl_cipher_filter=#{ssl_cipher_filter}"], @events)
 
-    ssl= @binder.instance_variable_get(:@ios)[0]
-    ctx = ssl.instance_variable_get(:@ctx)
-    assert_equal(keystore, ctx.keystore)
-    assert_equal(ssl_cipher_list, ctx.ssl_cipher_list)
+    assert_equal ssl_cipher_filter, ssl_context_for_binder(@binder).ssl_cipher_filter
   end
 
   def test_binder_parses_tlsv1_disabled
-    skip_on :jruby
-
-    key =  File.expand_path "../../examples/puma/puma_keypair.pem", __FILE__
-    cert = File.expand_path "../../examples/puma/cert_puma.pem", __FILE__
+    @binder.parse(["ssl://0.0.0.0?key=#{@key}&cert=#{@cert}&no_tlsv1=true"], @events)
 
-    @binder.parse(["ssl://0.0.0.0?key=#{key}&cert=#{cert}&no_tlsv1=true"], @events)
-
-    ssl = @binder.instance_variable_get(:@ios).first
-    ctx = ssl.instance_variable_get(:@ctx)
-    assert_equal(true, ctx.no_tlsv1)
+    assert ssl_context_for_binder(@binder).no_tlsv1
   end
 
   def test_binder_parses_tlsv1_enabled
-    skip_on :jruby
+    @binder.parse(["ssl://0.0.0.0?key=#{@key}&cert=#{@cert}&no_tlsv1=false"], @events)
 
-    key =  File.expand_path "../../examples/puma/puma_keypair.pem", __FILE__
-    cert = File.expand_path "../../examples/puma/cert_puma.pem", __FILE__
-
-    @binder.parse(["ssl://0.0.0.0?key=#{key}&cert=#{cert}&no_tlsv1=false"], @events)
-
-    ssl = @binder.instance_variable_get(:@ios).first
-    ctx = ssl.instance_variable_get(:@ctx)
-    refute(ctx.no_tlsv1)
+    refute ssl_context_for_binder(@binder).no_tlsv1
   end
 
   def test_binder_parses_tlsv1_unspecified_defaults_to_enabled
-    skip_on :jruby
-
-    key =  File.expand_path "../../examples/puma/puma_keypair.pem", __FILE__
-    cert = File.expand_path "../../examples/puma/cert_puma.pem", __FILE__
-
-    @binder.parse(["ssl://0.0.0.0?key=#{key}&cert=#{cert}"], @events)
+    @binder.parse(["ssl://0.0.0.0?key=#{@key}&cert=#{@cert}"], @events)
 
-    ssl = @binder.instance_variable_get(:@ios).first
-    ctx = ssl.instance_variable_get(:@ctx)
-    refute(ctx.no_tlsv1)
+    refute ssl_context_for_binder(@binder).no_tlsv1
   end
 end
diff --git a/test/test_cli.rb b/test/test_cli.rb
index cadefd097a..5140138665 100644
--- a/test/test_cli.rb
+++ b/test/test_cli.rb
@@ -87,8 +87,6 @@ def test_control_clustered
 
     wait_booted
 
-    sleep 2
-
     s = UNIXSocket.new @tmp_path
     s << "GET /stats HTTP/1.0\r\n\r\n"
     body = s.read
diff --git a/test/test_config.rb b/test/test_config.rb
index ae88bcda86..2fbef5ea07 100644
--- a/test/test_config.rb
+++ b/test/test_config.rb
@@ -1,12 +1,28 @@
+# frozen_string_literal: true
+
 require_relative "helper"
 
 require "puma/configuration"
 
-class TestConfigFile < Minitest::Test
-  def setup
-    FileUtils.mkpath("config/puma")
-    File.write("config/puma/fake-env.rb", "")
+class TestConfigFileBase < Minitest::Test
+  private
+
+  def with_env(env = {})
+    original_env = {}
+    env.each do |k, v|
+      original_env[k] = ENV[k]
+      ENV[k] = v
+    end
+    yield
+  ensure
+    original_env.each do |k, v|
+      ENV[k] = v
+    end
   end
+end
+
+class TestConfigFile < TestConfigFileBase
+  parallelize_me!
 
   def test_app_from_rackup
     conf = Puma::Configuration.new do |c|
@@ -46,19 +62,6 @@ def test_ssl_configuration_from_DSL
     assert_equal [200, {}, ["embedded app"]], app.call({})
   end
 
-  def test_double_bind_port
-    port = (rand(10_000) + 30_000).to_s
-    with_env("PORT" => port) do
-      conf = Puma::Configuration.new do |user_config, file_config, default_config|
-        user_config.bind "tcp://#{Puma::Configuration::DefaultTCPHost}:#{port}"
-        file_config.load "test/config/app.rb"
-      end
-
-      conf.load
-      assert_equal ["tcp://0.0.0.0:#{port}"], conf.options[:binds]
-    end
-  end
-
   def test_ssl_bind
     skip_on :jruby
 
@@ -168,24 +171,6 @@ def test_config_files_with_non_existing_path
     assert_equal ['test/config/typo/settings.rb'], conf.config_files
   end
 
-  def test_config_files_with_rack_env
-    with_env('RACK_ENV' => 'fake-env') do
-      conf = Puma::Configuration.new do
-      end
-
-      assert_equal ['config/puma/fake-env.rb'], conf.config_files
-    end
-  end
-
-  def test_config_files_with_specified_environment
-    conf = Puma::Configuration.new do
-    end
-
-    conf.options[:environment] = 'fake-env'
-
-    assert_equal ['config/puma/fake-env.rb'], conf.config_files
-  end
-
   def test_config_files_with_integer_convert
     conf = Puma::Configuration.new(config_files: ['test/config/with_integer_convert.rb']) do
     end
@@ -211,23 +196,49 @@ def test_config_raise_exception_on_sigterm
     conf.options[:raise_exception_on_sigterm] = true
     assert_equal conf.options[:raise_exception_on_sigterm], true
   end
+end
 
-  def teardown
-    FileUtils.rm_r("config/puma")
+# Thread unsafe modification of ENV
+class TestEnvModifificationConfig < TestConfigFileBase
+  def test_double_bind_port
+    port = (rand(10_000) + 30_000).to_s
+    with_env("PORT" => port) do
+      conf = Puma::Configuration.new do |user_config, file_config, default_config|
+        user_config.bind "tcp://#{Puma::Configuration::DefaultTCPHost}:#{port}"
+        file_config.load "test/config/app.rb"
+      end
+
+      conf.load
+      assert_equal ["tcp://0.0.0.0:#{port}"], conf.options[:binds]
+    end
   end
+end
 
-  private
+class TestConfigFileWithFakeEnv < TestConfigFileBase
+  def setup
+    FileUtils.mkpath("config/puma")
+    File.write("config/puma/fake-env.rb", "")
+  end
 
-    def with_env(env = {})
-      original_env = {}
-      env.each do |k, v|
-        original_env[k] = ENV[k]
-        ENV[k] = v
-      end
-      yield
-    ensure
-      original_env.each do |k, v|
-        ENV[k] = v
+  def test_config_files_with_rack_env
+    with_env('RACK_ENV' => 'fake-env') do
+      conf = Puma::Configuration.new do
       end
+
+      assert_equal ['config/puma/fake-env.rb'], conf.config_files
+    end
+  end
+
+  def test_config_files_with_specified_environment
+    conf = Puma::Configuration.new do
     end
+
+    conf.options[:environment] = 'fake-env'
+
+    assert_equal ['config/puma/fake-env.rb'], conf.config_files
+  end
+
+  def teardown
+    FileUtils.rm_r("config/puma")
+  end
 end
diff --git a/test/test_events.rb b/test/test_events.rb
index 8b91a69f84..98f3446d33 100644
--- a/test/test_events.rb
+++ b/test/test_events.rb
@@ -6,7 +6,6 @@ def test_null
 
     assert_instance_of Puma::NullIO, events.stdout
     assert_instance_of Puma::NullIO, events.stderr
-    assert_equal events.stdout, events.stderr
   end
 
   def test_strings
@@ -19,8 +18,17 @@ def test_strings
   def test_stdio
     events = Puma::Events.stdio
 
-    assert_equal STDOUT, events.stdout
-    assert_equal STDERR, events.stderr
+    # events.stdout is a dup, so same file handle, different ruby object, but inspect should show the same file handle
+    assert_equal STDOUT.inspect, events.stdout.inspect
+    assert_equal STDERR.inspect, events.stderr.inspect
+  end
+
+  def test_stdio_respects_sync
+    STDOUT.sync = false
+    events = Puma::Events.stdio
+
+    assert !STDOUT.sync
+    assert events.stdout.sync
   end
 
   def test_register_callback_with_block
@@ -156,4 +164,25 @@ def test_custom_log_formatter
 
     assert_equal "-> ready", out
   end
+
+  def test_parse_error
+    port = 0
+    host = "127.0.0.1"
+    app = proc { |env| [200, {"Content-Type" => "plain/text"}, ["hello\n"]] }
+    events = Puma::Events.strings
+    server = Puma::Server.new app, events
+
+    server.add_tcp_listener host, port
+    server.run
+
+    sock = TCPSocket.new host, server.connected_port
+    path = "/"
+    params = "a"*1024*10
+
+    sock << "GET #{path}?a=#{params} HTTP/1.1\r\nConnection: close\r\n\r\n"
+    sock.read
+    sleep 0.1 # important so that the previous data is sent as a packet
+    assert_match %r!HTTP parse error, malformed request \(#{path}\)!, events.stderr.string
+    server.stop(true)
+  end
 end
diff --git a/test/test_integration.rb b/test/test_integration.rb
index 78f4f01d8f..c07c308f42 100644
--- a/test/test_integration.rb
+++ b/test/test_integration.rb
@@ -6,6 +6,9 @@
 
 # These don't run on travis because they're too fragile
 
+# TODO: Remove over-utilization of @instance variables
+# TODO: remove stdout logging, get everything out of my rainbow dots
+
 class TestIntegration < Minitest::Test
 
   def setup
@@ -41,22 +44,25 @@ def teardown
     end
   end
 
-  def server(argv)
+  def server_cmd(argv)
     @tcp_port = next_port
     base = "#{Gem.ruby} -Ilib bin/puma"
-    base.prepend("bundle exec ") if defined?(Bundler)
-    cmd = "#{base} -b tcp://127.0.0.1:#{@tcp_port} #{argv}"
-    @server = IO.popen(cmd, "r")
+    base = "bundle exec #{base}" if defined?(Bundler)
+    "#{base} -b tcp://127.0.0.1:#{@tcp_port} #{argv}"
+  end
 
-    wait_for_server_to_boot
+  def server(argv)
+    @server = IO.popen(server_cmd(argv), "r")
+
+    wait_for_server_to_boot(@server)
 
     @server
   end
 
   def start_forked_server(argv)
-    @tcp_port = next_port
+    servercmd = server_cmd(argv)
     pid = fork do
-      exec "#{Gem.ruby} -I lib/ bin/puma -b tcp://127.0.0.1:#{@tcp_port} #{argv}"
+      exec servercmd
     end
 
     sleep 5
@@ -71,9 +77,9 @@ def stop_forked_server(pid)
 
   def restart_server_and_listen(argv)
     server(argv)
-    s = connect
-    initial_reply = read_body(s)
-    restart_server(s)
+    connection = connect
+    initial_reply = read_body(connection)
+    restart_server(@server, connection)
     [initial_reply, read_body(connect)]
   end
 
@@ -86,12 +92,12 @@ def wait_booted
   end
 
   # reuses an existing connection to make sure that works
-  def restart_server(connection)
+  def restart_server(server, connection)
     signal :USR2
 
     connection.write "GET / HTTP/1.1\r\n\r\n" # trigger it to start by sending a new request
 
-    wait_for_server_to_boot
+    wait_for_server_to_boot(server)
   end
 
   def connect
@@ -101,8 +107,8 @@ def connect
     s
   end
 
-  def wait_for_server_to_boot
-    true while @server.gets !~ /Ctrl-C/ # wait for server to say it booted
+  def wait_for_server_to_boot(server)
+    true while server.gets !~ /Ctrl-C/ # wait for server to say it booted
   end
 
   def read_body(connection)
@@ -204,7 +210,7 @@ def test_kill_unknown_via_pumactl
     skip_on :jruby
 
     # we run ls to get a 'safe' pid to pass off as puma in cli stop
-    # do not want to accidently kill a valid other process
+    # do not want to accidentally kill a valid other process
     io = IO.popen(windows? ? "dir" : "ls")
     safe_pid = io.pid
     Process.wait safe_pid
@@ -270,7 +276,7 @@ def test_sigterm_closes_listeners_on_forked_servers
         rescue Errno::ECONNREFUSED
           # connection was was never accepted
           # it can therefore be re-tried before the
-          # client receives an empty reponse
+          # client receives an empty response
           next_replies << :connection_refused
         end
       end
diff --git a/test/test_null_io.rb b/test/test_null_io.rb
index 5af9d6e0b1..c620cd0090 100644
--- a/test/test_null_io.rb
+++ b/test/test_null_io.rb
@@ -1,8 +1,12 @@
+# frozen_string_literal: true
+
 require_relative "helper"
 
 require "puma/null_io"
 
 class TestNullIO < Minitest::Test
+  parallelize_me!
+
   attr_accessor :nio
 
   def setup
@@ -18,7 +22,9 @@ def test_gets_returns_nil
   end
 
   def test_each_never_yields
-    nio.each { raise "never yield" }
+    nio.instance_variable_set(:@foo, :baz)
+    nio.each { @foo = :bar }
+    assert_equal :baz, nio.instance_variable_get(:@foo)
   end
 
   def test_read_with_no_arguments
diff --git a/test/test_persistent.rb b/test/test_persistent.rb
index 06ec90aa71..7144f72fc8 100644
--- a/test/test_persistent.rb
+++ b/test/test_persistent.rb
@@ -152,14 +152,14 @@ def test_one_with_keep_alive_header
   end
 
   def test_persistent_timeout
-    @server.persistent_timeout = 2
+    @server.persistent_timeout = 1
     @client << @valid_request
     sz = @body[0].size.to_s
 
     assert_equal "HTTP/1.1 200 OK\r\nX-Header: Works\r\nContent-Length: #{sz}\r\n\r\n", lines(4)
     assert_equal "Hello", @client.read(5)
 
-    sleep 3
+    sleep 2
 
     assert_raises EOFError do
       @client.read_nonblock(1)
diff --git a/test/test_puma_server.rb b/test/test_puma_server.rb
index 73a7190e40..7902850911 100644
--- a/test/test_puma_server.rb
+++ b/test/test_puma_server.rb
@@ -95,6 +95,30 @@ def test_very_large_return
   end
 
   def test_respect_x_forwarded_proto
+    env = {}
+    env['HOST'] = "example.com"
+    env['HTTP_X_FORWARDED_PROTO'] = "https,http"
+
+    assert_equal "443", @server.default_server_port(env)
+  end
+
+  def test_respect_x_forwarded_ssl_on
+    env = {}
+    env['HOST'] = "example.com"
+    env['HTTP_X_FORWARDED_SSL'] = "on"
+
+    assert_equal "443", @server.default_server_port(env)
+  end
+
+  def test_respect_x_forwarded_scheme
+    env = {}
+    env['HOST'] = "example.com"
+    env['HTTP_X_FORWARDED_SCHEME'] = "https"
+
+    assert_equal "443", @server.default_server_port(env)
+  end
+
+  def test_default_server_port
     @server.app = proc do |env|
       [200, {}, [env['SERVER_PORT']]]
     end
@@ -104,16 +128,15 @@ def test_respect_x_forwarded_proto
 
     req = Net::HTTP::Get.new("/")
     req['HOST'] = "example.com"
-    req['X_FORWARDED_PROTO'] = "https"
 
     res = Net::HTTP.start @host, @server.connected_port do |http|
       http.request(req)
     end
 
-    assert_equal "443", res.body
+    assert_equal "80", res.body
   end
 
-  def test_default_server_port
+  def test_default_server_port_respects_x_forwarded_proto
     @server.app = proc do |env|
       [200, {}, [env['SERVER_PORT']]]
     end
@@ -123,12 +146,13 @@ def test_default_server_port
 
     req = Net::HTTP::Get.new("/")
     req['HOST'] = "example.com"
+    req['X_FORWARDED_PROTO'] = "https,http"
 
     res = Net::HTTP.start @host, @server.connected_port do |http|
       http.request(req)
     end
 
-    assert_equal "80", res.body
+    assert_equal "443", res.body
   end
 
   def test_HEAD_has_no_body
diff --git a/test/test_rack_server.rb b/test/test_rack_server.rb
index 063d2f6253..d0fcac7db0 100644
--- a/test/test_rack_server.rb
+++ b/test/test_rack_server.rb
@@ -1,37 +1,31 @@
+# frozen_string_literal: true
 require_relative "helper"
 
 require "rack"
 
 class TestRackServer < Minitest::Test
+  parallelize_me!
 
   class ErrorChecker
     def initialize(app)
       @app = app
       @exception = nil
-      @env = nil
     end
 
     attr_reader :exception, :env
 
     def call(env)
       begin
-        @env = env
-        return @app.call(env)
+        @app.call(env)
       rescue Exception => e
         @exception = e
-
-        [
-          500,
-          { "X-Exception" => e.message, "X-Exception-Class" => e.class.to_s },
-          ["Error detected"]
-        ]
+        [ 500, {}, ["Error detected"] ]
       end
     end
   end
 
   class ServerLint < Rack::Lint
     def call(env)
-      assert("No env given") { env }
       check_env env
 
       @app.call(env)
@@ -39,8 +33,6 @@ def call(env)
   end
 
   def setup
-    @valid_request = "GET / HTTP/1.1\r\nHost: test.com\r\nContent-Type: text/plain\r\n\r\n"
-
     @simple = lambda { |env| [200, { "X-Header" => "Works" }, ["Hello"]] }
     @server = Puma::Server.new @simple
     @server.add_tcp_listener "127.0.0.1", 0
@@ -67,9 +59,7 @@ def test_lint
 
     stop
 
-    if exc = @checker.exception
-      raise exc
-    end
+    refute @checker.exception, "Checker raised exception"
   end
 
   def test_large_post_body
@@ -85,9 +75,7 @@ def test_large_post_body
 
     stop
 
-    if exc = @checker.exception
-      raise exc
-    end
+    refute @checker.exception, "Checker raised exception"
   end
 
   def test_path_info
@@ -134,5 +122,4 @@ def test_common_logger
 
     assert_match %r!GET /test HTTP/1\.1!, log.string
   end
-
 end
diff --git a/test/test_tcp_logger.rb b/test/test_tcp_logger.rb
index e6b31f7a13..ff9bf06994 100644
--- a/test/test_tcp_logger.rb
+++ b/test/test_tcp_logger.rb
@@ -18,6 +18,7 @@ def test_events
     # in lib/puma/launcher.rb:85
     # Puma::Events is default tcp_logger for cluster mode
     logger = Puma::Events.new(STDOUT, STDERR)
+    logger.instance_variable_set(:@stdout, $stdout) # ensure capture_process_io has access to the loggers output
     out, err = capture_subprocess_io do
       Puma::TCPLogger.new(logger, @server.app).call({}, @socket)
     end
diff --git a/test/test_thread_pool.rb b/test/test_thread_pool.rb
index f57dd2c8ad..7f2e65738b 100644
--- a/test/test_thread_pool.rb
+++ b/test/test_thread_pool.rb
@@ -5,11 +5,13 @@
 class TestThreadPool < Minitest::Test
 
   def teardown
-    @pool.shutdown if @pool
+    @pool.shutdown(1) if @pool
   end
 
   def new_pool(min, max, &block)
     block = proc { } unless block
+    @work_mutex = Mutex.new
+    @work_done = ConditionVariable.new
     @pool = Puma::ThreadPool.new(min, max, &block)
   end
 
@@ -22,18 +24,21 @@ def test_append_spawns
     thread_name = nil
 
     pool = new_pool(0, 1) do |work|
-      saw << work
-      thread_name = Thread.current.name if Thread.current.respond_to?(:name)
+      @work_mutex.synchronize do
+        saw << work
+        thread_name = Thread.current.name if Thread.current.respond_to?(:name)
+        @work_done.signal
+      end
     end
 
     pool << 1
 
-    pause
-
-    assert_equal [1], saw
-    assert_equal 1, pool.spawned
-    # Thread name is new in Ruby 2.3
-    assert_equal('puma 001', thread_name) if Thread.current.respond_to?(:name)
+    @work_mutex.synchronize do
+      @work_done.wait(@work_mutex, 5)
+      assert_equal 1, pool.spawned
+      assert_equal [1], saw
+      assert_equal('puma 001', thread_name) if Thread.current.respond_to?(:name)
+    end
   end
 
   def test_converts_pool_sizes
@@ -47,55 +52,60 @@ def test_converts_pool_sizes
   end
 
   def test_append_queues_on_max
-    finish = false
-    pool = new_pool(0, 1) { Thread.pass until finish }
+    pool = new_pool(0, 0) do
+      "Hello World!"
+    end
 
     pool << 1
     pool << 2
     pool << 3
 
-    pause
-
-    assert_equal 2, pool.backlog
-
-    finish = true
+    assert_equal 3, pool.backlog
   end
 
   def test_trim
-    pool = new_pool(0, 1)
+    pool = new_pool(0, 1) do |work|
+      @work_mutex.synchronize do
+        @work_done.signal
+      end
+    end
 
     pool << 1
 
-    pause
+    @work_mutex.synchronize do
+      @work_done.wait(@work_mutex, 5)
+      assert_equal 1, pool.spawned
+    end
 
-    assert_equal 1, pool.spawned
     pool.trim
+    pool.instance_variable_get(:@workers).first.join
 
-    pause
     assert_equal 0, pool.spawned
   end
 
   def test_trim_leaves_min
-    finish = false
-    pool = new_pool(1, 2) { Thread.pass until finish }
+    pool = new_pool(1, 2) do |work|
+      @work_mutex.synchronize do
+        @work_done.signal
+      end
+    end
 
     pool << 1
     pool << 2
 
-    finish = true
-
-    pause
+    @work_mutex.synchronize do
+      @work_done.wait(@work_mutex, 5)
+      assert_equal 2, pool.spawned
+    end
 
-    assert_equal 2, pool.spawned
     pool.trim
     pause
-
     assert_equal 1, pool.spawned
+
+
     pool.trim
     pause
-
     assert_equal 1, pool.spawned
-
   end
 
   def test_force_trim_doesnt_overtrim
@@ -215,16 +225,11 @@ def test_auto_reap_dead_threads
 
     assert_equal 2, pool.spawned
 
+    # TODO: is there a point to these two lines?
     pool << 1
     pool << 2
 
-    pause
-
-    assert_equal 2, pool.spawned
-
-    pool.auto_reap! 1
-
-    sleep 1
+    pool.auto_reap! 0.1
 
     pause
 
@@ -232,19 +237,22 @@ def test_auto_reap_dead_threads
   end
 
   def test_force_shutdown_immediately
-    pool = new_pool(1, 1) {
+    pool = new_pool(0, 1) do |work|
       begin
-        sleep 1
+        @work_mutex.synchronize do
+          @work_done.signal
+        end
+        sleep 10 # TODO: do something here other than sleep
       rescue Puma::ThreadPool::ForceShutdown
       end
-    }
+    end
 
     pool << 1
 
-    sleep 0.1
-
-    pool.shutdown(0)
-
-    assert_equal 0, pool.spawned
+    @work_mutex.synchronize do
+      @work_done.wait(@work_mutex, 5)
+      pool.shutdown(0)
+      assert_equal 0, pool.spawned
+    end
   end
 end
diff --git a/test/test_unix_socket.rb b/test/test_unix_socket.rb
index 712d6cdb4b..870a942356 100644
--- a/test/test_unix_socket.rb
+++ b/test/test_unix_socket.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require_relative "helper"
 
 class TestPumaUnixSocket < Minitest::Test
@@ -14,8 +16,7 @@ def setup
   end
 
   def teardown
-    @server.stop(true) if @server
-    File.unlink Path if File.exist? Path
+    @server.stop(true)
   end
 
   def test_server
@@ -26,7 +27,5 @@ def test_server
     expected = "HTTP/1.0 200 OK\r\nContent-Length: 5\r\n\r\nWorks"
 
     assert_equal expected, sock.read(expected.size)
-
-    sock.close
   end
 end
diff --git a/test/test_web_server.rb b/test/test_web_server.rb
index cc691b5bd3..4fd4b34803 100644
--- a/test/test_web_server.rb
+++ b/test/test_web_server.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 # Copyright (c) 2011 Evan Phoenix
 # Copyright (c) 2005 Zed A. Shaw
 
@@ -16,12 +17,10 @@ def call(env)
 end
 
 class WebServerTest < Minitest::Test
+  VALID_REQUEST = "GET / HTTP/1.1\r\nHost: www.zedshaw.com\r\nContent-Type: text/plain\r\n\r\n"
 
   def setup
-    @valid_request = "GET / HTTP/1.1\r\nHost: www.zedshaw.com\r\nContent-Type: text/plain\r\n\r\n"
-
     @tester = TestHandler.new
-
     @server = Puma::Server.new @tester, Puma::Events.strings
     @server.add_tcp_listener "127.0.0.1", 0
 
@@ -33,43 +32,24 @@ def teardown
   end
 
   def test_simple_server
-    hit(["http://127.0.0.1:#{ @server.connected_port }/test"])
+    hit(["http://127.0.0.1:#{@server.connected_port}/test"])
     assert @tester.ran_test, "Handler didn't really run"
   end
 
-
-  def do_test(string, chunk, close_after=nil, shutdown_delay=0)
-    # Do not use instance variables here, because it needs to be thread safe
-    socket = TCPSocket.new("127.0.0.1", @server.connected_port);
-    request = StringIO.new(string)
-    chunks_out = 0
-
-    while data = request.read(chunk)
-      chunks_out += socket.write(data)
-      socket.flush
-      sleep 0.2
-      if close_after and chunks_out > close_after
-        socket.close
-        sleep 1
-      end
-    end
-    sleep(shutdown_delay)
-    socket.write(" ") # Some platforms only raise the exception on attempted write
-    socket.flush
-  end
-
   def test_trickle_attack
-    do_test(@valid_request, 3)
+    socket = do_test(VALID_REQUEST, 3)
+    assert_match "hello", socket.read
   end
 
   def test_close_client
     assert_raises IOError do
-      do_test(@valid_request, 10, 20)
+      do_test(VALID_REQUEST, 10, 20)
     end
   end
 
   def test_bad_client
-    do_test("GET /test HTTP/BAD", 3)
+    socket = do_test("GET /test HTTP/BAD", 3)
+    assert_match "Bad Request", socket.read
   end
 
   def test_header_is_too_long
@@ -79,10 +59,30 @@ def test_header_is_too_long
     end
   end
 
+  # TODO: Why does this test take exactly 20 seconds?
   def test_file_streamed_request
     body = "a" * (Puma::Const::MAX_BODY * 2)
     long = "GET /test HTTP/1.1\r\nContent-length: #{body.length}\r\n\r\n" + body
-    do_test(long, (Puma::Const::CHUNK_SIZE * 2) - 400)
+    socket = do_test(long, (Puma::Const::CHUNK_SIZE * 2) - 400)
+    assert_match "hello", socket.read
   end
 
+  private
+
+  def do_test(string, chunk, close_after=nil)
+    # Do not use instance variables here, because it needs to be thread safe
+    socket = TCPSocket.new("127.0.0.1", @server.connected_port);
+    request = StringIO.new(string)
+    chunks_out = 0
+
+    while data = request.read(chunk)
+      chunks_out += socket.write(data)
+      socket.flush
+      socket.close if close_after && chunks_out > close_after
+    end
+
+    socket.write(" ") # Some platforms only raise the exception on attempted write
+    socket.flush
+    socket
+  end
 end
diff --git a/tools/jungle/init.d/puma b/tools/jungle/init.d/puma
index 5f9e036f9a..32fe85d683 100755
--- a/tools/jungle/init.d/puma
+++ b/tools/jungle/init.d/puma
@@ -398,7 +398,7 @@ case "$1" in
   ;;
   remove)
     if [ "$#" -lt 2 ]; then
-      echo "Please, specifiy the app's directory to remove."
+      echo "Please, specify the app's directory to remove."
       exit 1
     else
       do_remove $2
diff --git a/win_gem_test/puma.ps1 b/win_gem_test/puma.ps1
index 60a6275353..89fbfce457 100644
--- a/win_gem_test/puma.ps1
+++ b/win_gem_test/puma.ps1
@@ -37,7 +37,7 @@ function Pre-Compile {
 #———————————————————————————————————————————————————————————————— Run-Tests
 function Run-Tests {
   # call with comma separated list of gems to install or update
-  Update-Gems minitest, minitest-retry, rack, rake
+  Update-Gems minitest, minitest-retry, minitest-proveit, rack, rake
   $env:CI = 1
   rake -f Rakefile_wintest -N -R norakelib | Set-Content -Path $log_name -PassThru -Encoding UTF8
   # add info after test results