diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5fe6fac..31c202c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,6 +2,7 @@ name: CI
 on:
   push:
     paths:
+      - 'run-specs-in-docker.sh'
       - '.github/workflows/ci.yml'
       - 'shard.yml'
       - 'shard.lock'
@@ -12,28 +13,17 @@ on:
 jobs:
   spec:
     runs-on: ubuntu-latest
-    container: 84codes/crystal:latest-ubuntu-22.04
+    timeout-minutes: 10
     steps:
-      - name: Install RabbitMQ
-        run: apt-get update && apt-get install -y rabbitmq-server
-
-      - name: Start RabbitMQ
-        run: RABBITMQ_PID_FILE=/tmp/rabbitmq.pid rabbitmq-server -detached
-
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Install shards
-        run: sed -i '/ameba/d' shard.yml && shards install
-
-      - name: Wait for RabbitMQ to start
-        run: rabbitmqctl wait /tmp/rabbitmq.pid
-
       - name: Run tests
-        run: crystal spec --order random
+        run: ./run-specs-in-docker.sh
 
   lint:
     runs-on: ubuntu-latest
+    timeout-minutes: 10
     container: 84codes/crystal:latest-ubuntu-22.04
     steps:
       - uses: actions/checkout@v4
@@ -42,6 +32,7 @@ jobs:
 
   format:
     runs-on: ubuntu-latest
+    timeout-minutes: 10
     container: 84codes/crystal:latest-ubuntu-22.04
     steps:
       - uses: actions/checkout@v4
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index fea75b7..e39f7f9 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -1,6 +1,25 @@
 # Contributing
 
-_TODO_
+## Development
+
+Run tests in Docker:
+
+```bash
+docker build  . -f spec/Dockerfile -t amqproxy_spec
+docker run --rm -it -v $(pwd):/app -w /app --entrypoint bash amqproxy_spec
+
+# ensure rabbitmq is up, run all specs
+./entrypoint.sh
+
+# run single spec
+crystal spec --example "keeps connections open"
+```
+
+Run tests using Docker Compose:
+
+```bash
+./run-specs-in-docker.sh
+```
 
 ## Release
 
diff --git a/run-specs-in-docker.sh b/run-specs-in-docker.sh
new file mode 100755
index 0000000..8a1d756
--- /dev/null
+++ b/run-specs-in-docker.sh
@@ -0,0 +1,13 @@
+#!/bin/bash
+
+set -x
+set -e
+
+docker compose \
+  --file spec/docker-compose.yml \
+  up \
+  --remove-orphans \
+  --force-recreate \
+  --renew-anon-volumes \
+  --build \
+  --exit-code-from spec
diff --git a/spec/Dockerfile b/spec/Dockerfile
new file mode 100644
index 0000000..2543d4a
--- /dev/null
+++ b/spec/Dockerfile
@@ -0,0 +1,16 @@
+FROM 84codes/crystal:latest-ubuntu-22.04
+
+RUN apt-get update && apt-get install -y rabbitmq-server
+
+WORKDIR /tmp
+
+# We want to install shards before copying code/spec files for quicker runs
+COPY shard.yml shard.lock ./
+RUN shards install
+
+COPY src/ src/
+COPY spec/ spec/
+
+COPY spec/entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+ENTRYPOINT ["/entrypoint.sh"]
diff --git a/spec/amqproxy_spec.cr b/spec/amqproxy_spec.cr
index f5f7477..dce0f5b 100644
--- a/spec/amqproxy_spec.cr
+++ b/spec/amqproxy_spec.cr
@@ -21,6 +21,44 @@ describe AMQProxy::Server do
     end
   end
 
+  it "publish and consume works" do
+    server = AMQProxy::Server.new("127.0.0.1", 5672, false, Logger::DEBUG)
+    begin
+      spawn { server.listen("127.0.0.1", 5673) }
+      Fiber.yield
+
+      queue_name = "amqproxy-test-queue"
+      num_received_messages = 0
+      num_messages_to_publish = 5
+
+      num_messages_to_publish.times do
+        AMQP::Client.start("amqp://localhost:5673") do |conn|
+          channel = conn.channel
+          queue = channel.queue(queue_name)
+          queue.publish_confirm("Message from AMQProxy specs")
+        end
+        sleep 0.1
+      end
+
+      AMQP::Client.start("amqp://localhost:5673") do |conn|
+        channel = conn.channel
+        channel.basic_consume(queue_name, tag: "AMQProxy specs") do |msg|
+          body = msg.body_io.to_s
+          if body == "Message from AMQProxy specs"
+            # FIXME: ack:ing causes this bug
+            # https://github.com/cloudamqp/amqproxy/issues/137
+            # channel.basic_ack(msg.delivery_tag)
+            num_received_messages += 1
+          end
+        end
+      end
+
+      num_received_messages.should eq num_messages_to_publish
+    ensure
+      server.stop_accepting_clients
+    end
+  end
+
   it "can reconnect if upstream closes" do
     s = AMQProxy::Server.new("127.0.0.1", 5672, false, Logger::DEBUG)
     begin
diff --git a/spec/docker-compose.yml b/spec/docker-compose.yml
new file mode 100644
index 0000000..a27c3c8
--- /dev/null
+++ b/spec/docker-compose.yml
@@ -0,0 +1,6 @@
+version: "3.8"
+services:
+  spec:
+    build:
+      context: ..
+      dockerfile: spec/Dockerfile
diff --git a/spec/entrypoint.sh b/spec/entrypoint.sh
new file mode 100644
index 0000000..0ad1022
--- /dev/null
+++ b/spec/entrypoint.sh
@@ -0,0 +1,16 @@
+#!/bin/bash
+
+set -e
+set -u
+set -x
+
+export RABBITMQ_PID_FILE=/tmp/rabbitmq.pid
+
+# Start RabbitMQ
+rabbitmq-server -detached
+
+# Wait for RabbitMQ to start
+rabbitmqctl wait $RABBITMQ_PID_FILE
+
+crystal --version
+crystal spec --order random
diff --git a/spec/spec_helper.cr b/spec/spec_helper.cr
index 924f505..d0978b6 100644
--- a/spec/spec_helper.cr
+++ b/spec/spec_helper.cr
@@ -4,3 +4,33 @@ require "../src/amqproxy/version"
 require "amqp-client"
 
 MAYBE_SUDO = (ENV.has_key?("NO_SUDO") || `id -u` == "0\n") ? "" : "sudo "
+
+# Spec timeout borrowed from Crystal project:
+# https://github.com/crystal-lang/crystal/blob/1.10.1/spec/support/mt_abort_timeout.cr
+
+private SPEC_TIMEOUT = 15.seconds
+
+Spec.around_each do |example|
+  done = Channel(Exception?).new
+
+  spawn(same_thread: true) do
+    begin
+      example.run
+    rescue e
+      done.send(e)
+    else
+      done.send(nil)
+    end
+  end
+
+  timeout = SPEC_TIMEOUT
+
+  select
+  when res = done.receive
+    raise res if res
+  when timeout(timeout)
+    _it = example.example
+    ex = Spec::AssertionFailed.new("spec timed out after #{timeout}", _it.file, _it.line)
+    _it.parent.report(:fail, _it.description, _it.file, _it.line, timeout, ex)
+  end
+end
diff --git a/src/amqproxy/upstream.cr b/src/amqproxy/upstream.cr
index 6d09105..a588faa 100644
--- a/src/amqproxy/upstream.cr
+++ b/src/amqproxy/upstream.cr
@@ -40,7 +40,6 @@ module AMQProxy
     # Frames from upstream (to client)
     def read_loop # ameba:disable Metrics/CyclomaticComplexity
       socket = @socket
-      client = @current_client
       loop do
         AMQ::Protocol::Frame.from_io(socket, IO::ByteFormat::NetworkEndian) do |frame|
           case frame
@@ -56,7 +55,7 @@ module AMQProxy
             write frame
             next
           end
-          if client
+          if client = @current_client
             begin
               client.write(frame)
             rescue ex
@@ -85,7 +84,7 @@ module AMQProxy
       @log.error "Error reading from upstream: #{ex.inspect_with_backtrace}" unless @socket.closed?
     ensure
       @socket.close unless @socket.closed?
-      client.close_socket if client
+      @current_client.try &.close_socket
     end
 
     SAFE_BASIC_METHODS = {40, 10} # qos and publish