MMDSmart

Senior Manual QA Engineer – VoIP, Voice, Real-Time Communications

MMDSmart

full-time

Posted on:

Location Type: Remote

Location: Poland

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Job Level

Senior

Tech Stack

FirewallsJavaScriptJMeterLinuxPythonTCP/IPTypeScriptVoIP

About the role

  • You will analyze business requirements and technical specifications for both web interfaces and backend, proactively challenging architectural assumptions to prevent issues before they reach production.
  • You will act as a "Voice System Investigator" performing deep-dive analysis of complex call flows and media streams using packet captures (PCAPs) and server logs to identify the root cause of signaling and audio defects.
  • You will design and execute advanced test strategies that cover the entire communication lifecycle, ensuring seamless integration between WebRTC components, IVR logic, ACD routing, and call recording systems.
  • You will investigate the intersection of web application states and real-time media, debugging issues like UI/UX synchronization with agent states, call control race conditions, and WebRTC connectivity hurdles.
  • You will proactively simulate network impairments (latency, jitter, packet loss) and use voice quality metrics (MOS) to ensure the system remains resilient and high-performing under sub-optimal conditions.
  • You will drive quality improvements within an Agile environment, participating in architectural reviews and brainstorming sessions to advocate for testability and system stability.
  • You will mentor the team and improve QA processes, sharing your expertise in troubleshooting stateful, event-driven systems and helping to refine estimation and testing methodologies.
  • You will maintain technical documentation and RCA (Root Cause Analysis) reports, ensuring that complex "hard-to-reproduce" bugs are well-documented and that the team learns from every critical leak.

Requirements

  • 5+ years of software testing experience, with at least 2+ years in VoIP / Voice / real-time communication systems.
  • Strong hands-on understanding of SIP protocol (call flows, registrations, INVITE flows, SDP, RTP).
  • Practical experience analyzing SIP/RTP traffic.
  • Experience testing call center / CCaaS systems (IVR flows; ACD / call routing logic; Call recording; Agent states & call lifecycle).
  • Familiarity with WebRTC technologies and real-time communication challenges.
  • Deep understanding of voice quality metrics (latency, jitter, packet loss, echo, MOS).
  • Solid knowledge of TCP/IP networking, NAT, firewalls, ports, STUN/TURN.
  • Experience working in Linux environments and reading server logs.
  • Basic scripting skills in Python / JS / TS for test tooling and log analysis.
  • Experience with REST API testing (Postman, curl, or similar).
  • Understanding of RTP media flow vs SIP signaling.
  • Ability to debug one-way audio, no audio, delayed media, early media.
  • Experience testing systems that depend on timing, network conditions, and concurrency.
  • Understanding how telephony behaves differently from web applications (stateful, event-driven, race conditions).
  • Nice to have: Experience with test automation using Playwright or similar.
  • Nice to have: Experience with API automation frameworks (pytest, REST Assured, etc.).
  • Nice to have: Familiarity with performance / load tools: (k6, JMeter, Locust).
  • Nice to have: Experience simulating SIP traffic using SIPp.
  • Nice to have: Experience working with PBX / SBC / softswitches (Asterisk, FreeSWITCH, Zoiper, etc.).
  • Nice to have: Experience testing under network impairment (packet loss / delay simulation).
Benefits
  • Your Wellness: Access to mental health programs, comprehensive medical insurance, and a sports card.
  • Your Happiness: Enjoy the company of cool teammates, a friendly atmosphere, a strong mentorship, and a variety of bonuses & corporate gifts.
  • Your Development: Benefit from free educational events & courses, and English classes with native speakers.
  • Your Career: Focus on your professional development in a supportive environment.
  • Work-Life Balance: Choose your working format - remote, office-based, or hybrid and engage in team-building activities.
Applicant Tracking System Keywords

Tip: use these terms in your resume and cover letter to boost ATS matches.

Hard Skills & Tools
software testingVoIPSIP protocolSIP/RTP traffic analysiscall center systemsWebRTCvoice quality metricsTCP/IP networkingscripting in PythonREST API testing
Soft Skills
analytical skillsmentoringtroubleshootingcommunicationcollaborationproblem-solvingadvocacy for testabilityprocess improvementdocumentationteamwork