diff --git a/spec/lib/runner/strategy/poseidon/connection_spec.rb b/spec/lib/runner/strategy/poseidon/connection_spec.rb
new file mode 100644
index 00000000..15704a1f
--- /dev/null
+++ b/spec/lib/runner/strategy/poseidon/connection_spec.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe Runner::Strategy::Poseidon::Connection do
+  let(:runner_id) { attributes_for(:runner)[:runner_id] }
+  let(:execution_environment) { create(:ruby) }
+  let(:strategy) { Runner::Strategy::Poseidon.new(runner_id, execution_environment) }
+  let(:connection_url) { 'wss://runners.example.org/websocket' }
+  let(:connection) { described_class.new(connection_url, strategy, nil) }
+  let(:websocket_client) { instance_double(Faye::WebSocket::Client) }
+
+  before do
+    allow(Faye::WebSocket::Client).to receive(:new).and_return(websocket_client)
+    allow(websocket_client).to receive(:on)
+    allow(websocket_client).to receive(:url).and_return(connection_url)
+  end
+
+  describe '#on_message' do
+    subject(:process_message) { connection.send(:on_message, websocket_event, nil) }
+
+    let(:websocket_event) { Faye::WebSocket::API::Event.create('message', data: message.to_json) }
+
+    before { allow(connection).to receive(:on_message).and_call_original }
+
+    shared_examples 'calls a message handler' do
+      it 'calls the corresponding handler' do
+        handler = "handle_#{message[:type]}".to_sym
+        expect(connection).to receive(handler)
+        process_message
+      end
+    end
+
+    context "when type is 'start'" do
+      let(:message) { {type: 'start'} }
+
+      it_behaves_like 'calls a message handler'
+    end
+
+    context "when type is 'stdout'" do
+      let(:message) { {type: 'stdout', data: 'Standard Output'} }
+
+      it_behaves_like 'calls a message handler'
+    end
+
+    context "when type is 'stderr'" do
+      let(:message) { {type: 'stderr', data: 'Standard Error'} }
+
+      it_behaves_like 'calls a message handler'
+    end
+
+    context "when type is 'error'" do
+      let(:message) { {type: 'error', data: 'Error'} }
+
+      it_behaves_like 'calls a message handler'
+    end
+
+    context "when type is 'exit'" do
+      let(:message) { {type: 'exit', data: 0} }
+
+      it_behaves_like 'calls a message handler'
+    end
+
+    context "when type is 'timeout'" do
+      let(:message) { {type: 'timeout'} }
+
+      it_behaves_like 'calls a message handler'
+    end
+  end
+end