diff --git a/docker-compose.yml b/docker-compose.yml
index a225749..e7bac22 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -36,7 +36,12 @@ services:
       - ./server/run.sh:/app/run.sh
 
   tests:
-    build: ./tests
+    build:
+      context: ./tests
+      args:
+        faraday_gem_ref: ${FARADAY_GEM_REF:-master}
+        faraday_http_gem_ref: ${FARADAY_HTTP_GEM_REF:-master}
+        socksify_gem_ref: ${FARADAY_SOCKSIFY_GEM_REF:-master}
     depends_on:
       - server
       - proxy
@@ -45,9 +50,9 @@ services:
     environment:
       - HTTP_HOST=faraday-live.localhost
       - PROXY_HOST=live-proxy.localhost
-      - FARADAY_ADAPTER=${TEST_ADAPTER:-}
-      - FARADAY_METHOD=${TEST_METHOD:-}
-      - SERVER_PROTOCOL=${TEST_PROTO:-}
+      - TEST_ADAPTER=${TEST_ADAPTER:-}
+      - TEST_METHOD=${TEST_METHOD:-}
+      - TEST_PROTO=${TEST_PROTO:-}
     volumes:
       - certca:/root/.local/share/mkcert/:ro
       - certdata:/certs:ro
diff --git a/docs/dev.md b/docs/dev.md
index f7b9675..186dff0 100644
--- a/docs/dev.md
+++ b/docs/dev.md
@@ -38,7 +38,9 @@ This runs tests against these webservers and proxies:
 1. HTTP server on port 80 (`TEST_PROTO=http`)
 2. Self-signed HTTPS server on port 443 (`TEST_PROTO=unverified`)
 3. Verified and valid HTTPS server on port 443 (`TEST_PROTO=https`)
-4. Proxy server (`TEST_PROTO=proxy`)
+4. HTTP proxy server (`TEST_PROTO=http_proxy`)
+5. SOCKS proxy server (`TEST_PROTO=socks_proxy`)
+6. LEGACY: Only HTTP proxy server (`TEST_PROTO=proxy`)
 
 You can choose to run one or more explicitly:
 
diff --git a/proxy/Dockerfile b/proxy/Dockerfile
index 9900d25..231d35f 100644
--- a/proxy/Dockerfile
+++ b/proxy/Dockerfile
@@ -1,5 +1,6 @@
 FROM golang:1.12.3
 RUN go get -u github.com/elazarl/goproxy
+RUN go get -u github.com/armon/go-socks5
 
 # no auth, http
 EXPOSE 8080
@@ -13,6 +14,12 @@ EXPOSE 9080
 # auth:pass, https
 EXPOSE 9080
 
+# no auth, socks
+EXPOSE 6000
+
+# auth:pass, socks
+EXPOSE 6001
+
 WORKDIR /app
 COPY . ./
 RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o proxy .
diff --git a/proxy/main.go b/proxy/main.go
index 5db204c..26def33 100644
--- a/proxy/main.go
+++ b/proxy/main.go
@@ -5,6 +5,8 @@ import (
 	"flag"
 	"log"
 	"net/http"
+
+	socks5 "github.com/armon/go-socks5"
 )
 
 var (
@@ -15,6 +17,24 @@ var (
 func main() {
 	flag.Parse()
 
+	unauthSocks, err := socks5.New(&socks5.Config{})
+	if err != nil {
+		panic(err)
+	}
+
+	authSocks, err := socks5.New(&socks5.Config{
+		Credentials: socks5.StaticCredentials(map[string]string{
+			"faraday": "live",
+		}),
+	})
+	if err != nil {
+		panic(err)
+	}
+
+	log.Println("Starting Socks Proxy servers on :6000, :6001...")
+	go unauthSocks.ListenAndServe("tcp", ":6000")
+	go authSocks.ListenAndServe("tcp", ":6001")
+
 	servers := &ServerList{}
 	servers.Add(":8080", newProxy("http_proxy"))
 	servers.Add(":9080", newProxy("http_auth_proxy"))
@@ -39,7 +59,7 @@ func (l *ServerList) Listen() {
 }
 
 func (l *ServerList) listen(srv *http.Server) {
-	log.Printf("Starting Proxy server on %s...", srv.Addr)
+	log.Printf("Starting HTTP Proxy server on %s...", srv.Addr)
 	if srv.TLSConfig == nil {
 		srv.ListenAndServe()
 		return
diff --git a/tests/Dockerfile b/tests/Dockerfile
index c4be577..d8d1f55 100644
--- a/tests/Dockerfile
+++ b/tests/Dockerfile
@@ -2,22 +2,28 @@
 FROM ruby:2.6.2 as build
 ENV LANG C.UTF-8
 WORKDIR /app
-COPY Gemfile .
-COPY Gemfile.lock .
 
 # install all non-git gems
 RUN gem install bundler -v '~> 2.0.1' --no-document
-RUN bundle install --without development test -j4 --retry 3
 
-ARG faraday_gem_ref=master
-ARG faraday_http_gem_ref=master
+COPY Gemfile .
+COPY Gemfile.lock .
+
+RUN bundle install --without development test -j4 --retry 3
 
 # install just the non-git gems. These will change more frequently.
 RUN echo "gem 'faraday', git: 'https://github.com/lostisland/faraday'," >> Gemfile
+ARG faraday_gem_ref=master
 RUN echo "  ref: '$faraday_gem_ref', require: 'faraday'" >> Gemfile
+
 RUN echo "gem 'faraday-http', git: 'https://github.com/lostisland/faraday-http'," >> Gemfile
+ARG faraday_http_gem_ref=master
 RUN echo "  ref: '$faraday_http_gem_ref', require: 'faraday/http'" >> Gemfile
 
+RUN echo "gem 'socksify', git: 'https://github.com/astro/socksify-ruby'," >> Gemfile
+ARG socksify_gem_ref=master
+RUN echo "  ref: '$socksify_gem_ref'" >> Gemfile
+
 RUN bundle install \
   # Remove unneeded files (cached *.gem, *.o, *.c)
   && rm -rf /usr/local/bundle/cache/*.gem \
diff --git a/tests/spec/insecure_spec.rb b/tests/spec/insecure_spec.rb
index 21385d2..679f860 100644
--- a/tests/spec/insecure_spec.rb
+++ b/tests/spec/insecure_spec.rb
@@ -10,15 +10,30 @@
       proxy: :http_proxy,
       server: :http,
     }
-  end if ServerProtocols.proxy?
+  end if ServerProtocols.http_proxy?
+
+  describe "#{adapter} using Socks proxy with HTTP server" do
+    include_examples 'a proxied connection', adapter, {
+      proxy: :socks_proxy,
+      server: :http,
+    }
+  end if ServerProtocols.socks_proxy? && adapter.socks_proxy?
 
   describe "#{adapter} using authenticated HTTP proxy with HTTP server" do
     include_examples 'a proxied connection', adapter, {
       proxy: :http_auth_proxy,
       server: :http,
-        auth: "faraday:live",
+      auth: "faraday:live",
+    }
+  end if ServerProtocols.http_proxy?
+
+  describe "#{adapter} using authenticated Socks proxy with HTTP server" do
+    include_examples 'a proxied connection', adapter, {
+      proxy: :socks_auth_proxy,
+      server: :http,
+      auth: "faraday:live",
     }
-  end if ServerProtocols.proxy?
+  end if ServerProtocols.socks_proxy? && adapter.socks_proxy?
 
   describe "#{adapter} with unverified HTTPS server" do
     let(:url_kind) { :https }
diff --git a/tests/spec/secure_spec.rb b/tests/spec/secure_spec.rb
index fe53cac..feb6d14 100644
--- a/tests/spec/secure_spec.rb
+++ b/tests/spec/secure_spec.rb
@@ -10,15 +10,30 @@
       proxy: :http_proxy,
       server: :https,
     }
-  end if ServerProtocols.proxy?
+  end if ServerProtocols.http_proxy?
 
-  describe "#{adapter} using HTTP proxy with HTTPS server" do
+  describe "#{adapter} using authenticated HTTP proxy with HTTPS server" do
     include_examples 'a proxied connection', adapter, {
       proxy: :http_auth_proxy,
       server: :https,
       auth: "faraday:live",
     }
-  end if ServerProtocols.proxy?
+  end if ServerProtocols.http_proxy?
+
+  describe "#{adapter} using Socks proxy with HTTPS server" do
+    include_examples 'a proxied connection', adapter, {
+      proxy: :socks_proxy,
+      server: :https,
+    }
+  end if ServerProtocols.socks_proxy? && adapter.socks_proxy?
+
+  describe "#{adapter} using authenticated Socks proxy with HTTPS server" do
+    include_examples 'a proxied connection', adapter, {
+      proxy: :socks_auth_proxy,
+      server: :https,
+      auth: "faraday:live",
+    }
+  end if ServerProtocols.socks_proxy? && adapter.socks_proxy?
 
   describe "#{adapter} using HTTPS proxy with HTTPS server" do
     it "fails to connect" do
@@ -29,7 +44,7 @@
       end
       expect { conn.get 'wat' }.to raise_error(Faraday::ConnectionFailed)
     end
-  end if ServerProtocols.proxy? && !adapter.https_proxy_bug?
+  end if ServerProtocols.http_proxy? && !adapter.https_proxy_bug?
 
   describe "#{adapter} using authenticated HTTPS proxy with HTTPS server" do
     it "fails to connect" do
@@ -40,5 +55,5 @@
       end
       expect { conn.get 'wat' }.to raise_error(Faraday::ConnectionFailed)
     end
-  end if ServerProtocols.proxy? && !adapter.https_proxy_bug?
+  end if ServerProtocols.http_proxy? && !adapter.https_proxy_bug?
 end
diff --git a/tests/spec/support/adapters.rb b/tests/spec/support/adapters.rb
index 07ff6de..e76c4ee 100644
--- a/tests/spec/support/adapters.rb
+++ b/tests/spec/support/adapters.rb
@@ -28,7 +28,7 @@ def self.adapter_keys
   end
 
   def self.explicit_adapters
-    ENV['FARADAY_ADAPTER'].to_s.split(',').map! do |key|
+    ENV['TEST_ADAPTER'].to_s.split(',').map! do |key|
       key.strip!
       key.downcase!
       key.to_sym
@@ -52,6 +52,7 @@ def to_s
       :connect_with_response_body, # enables CONNECT tests WITH response body
       :unverified_https_bug, # https://github.com/technoweenie/faraday-live/issues/4
       :https_proxy_bug, # https://github.com/technoweenie/faraday-live/issues/6
+      :socks_proxy,
     ].each do |feature|
       define_method("#{feature}?") { @features.include?(feature) }
     end
@@ -81,7 +82,7 @@ def connect_method?
       :trace_method, :connect_with_response_body),
 
     :net_http => Adapter.new(:net_http,
-      :trace_method, :connect_with_response_body),
+      :socks_proxy, :trace_method, :connect_with_response_body),
 
     :patron => Adapter.new(:patron,
       :unverified_https_bug),
diff --git a/tests/spec/support/examples/proxy.rb b/tests/spec/support/examples/proxy.rb
index 3cd722b..ca4564e 100644
--- a/tests/spec/support/examples/proxy.rb
+++ b/tests/spec/support/examples/proxy.rb
@@ -25,7 +25,12 @@
   end
 
   # proxy does not modify https requests
-  expected = server_url_kind == :https ? '' : "goproxy (#{proxy_url_kind})"
+  expected = case proxy_url_kind
+  when :socks_proxy, :socks_auth_proxy
+    ""
+  else
+    server_url_kind == :https ? "" : "goproxy (#{proxy_url_kind})"
+  end
   include_examples 'common request tests', server_url_kind, adapter,
     response_header: {
       'Via' => expected,
diff --git a/tests/spec/support/http_methods.rb b/tests/spec/support/http_methods.rb
index 1d22018..c920b35 100644
--- a/tests/spec/support/http_methods.rb
+++ b/tests/spec/support/http_methods.rb
@@ -29,7 +29,7 @@ def self.http_methods!
   end
 
   def self.explicit_methods
-    ENV['FARADAY_METHOD'].to_s.split(',').map! do |key|
+    ENV['TEST_METHOD'].to_s.split(',').map! do |key|
       key.strip!
       key.downcase!
       key.to_sym
diff --git a/tests/spec/support/protocols.rb b/tests/spec/support/protocols.rb
index b14728f..0433a35 100644
--- a/tests/spec/support/protocols.rb
+++ b/tests/spec/support/protocols.rb
@@ -13,8 +13,12 @@ def self.unverified_https?
     protocols.include?(:unverified)
   end
 
-  def self.proxy?
-    protocols.include?(:proxy)
+  def self.http_proxy?
+    protocols.include?(:proxy) || protocols.include?(:http_proxy)
+  end
+
+  def self.socks_proxy?
+    protocols.include?(:socks_proxy)
   end
 
   def self.test?(*protos)
@@ -34,7 +38,7 @@ def self.protocols!
   end
 
   def self.explicit_protocols
-    ENV['SERVER_PROTOCOL'].to_s.split(',').map! do |key|
+    ENV['TEST_PROTO'].to_s.split(',').map! do |key|
       key.strip!
       key.downcase!
       key.to_sym
diff --git a/tests/spec/support/urls.rb b/tests/spec/support/urls.rb
index 4cd6ffd..86aa2aa 100644
--- a/tests/spec/support/urls.rb
+++ b/tests/spec/support/urls.rb
@@ -33,4 +33,14 @@ def self.https_auth_proxy_server(auth = nil)
     auth += "@" if auth
     "http://#{auth}#{ENV['PROXY_HOST']}:9443"
   end
+
+  def self.socks_proxy_server(auth = nil)
+    auth += "@" if auth
+    "socks://#{auth}#{ENV['PROXY_HOST']}:6000"
+  end
+
+  def self.socks_auth_proxy_server(auth = nil)
+    auth += "@" if auth
+    "socks://#{auth}#{ENV['PROXY_HOST']}:6001"
+  end
 end