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Senior Manual QA Engineer (VoIP / Voice / Real-Time Communications)

3 weeks ago
Serbia, Georgia, Kazakhstan, Bosnia and Herzegovina, Czech Republic, Poland
Full-time
Senior
QA Engineer
Software Development
Agile JavaScript JMeter K6 Linux Locust Playwright Postman Pytest Python REST API TCP/IP TypeScript WebRTC
Apply Now
MMDSmart

MMDSmart

MMDSmart provides enterprise communication services and platforms, including telecom VoIP, mobile messaging, and call center solutions, to businesses worldwide.

Communications Equipment
51-250
Founded 2007
View All Jobs 10

Description

  • Analyze business requirements and technical specifications for web interfaces and backend systems.
  • Act as a voice system investigator to perform deep-dive analysis of complex call flows and media streams.
  • Use packet captures, server logs, and related diagnostics to identify the root cause of signaling and audio defects.
  • Design and execute advanced test strategies across the full communication lifecycle.
  • Validate integration between WebRTC components, IVR logic, ACD routing, and call recording systems.
  • Investigate issues at the intersection of web application states and real-time media, including synchronization and call-control race conditions.
  • Simulate network impairments such as latency, jitter, and packet loss, and assess voice quality using MOS and related metrics.
  • Participate in Agile architectural reviews and brainstorming sessions to improve testability and system stability.
  • Mentor the team, improve QA processes, and help refine estimation and testing methodologies.
  • Maintain technical documentation and RCA reports for hard-to-reproduce defects and critical issues.

Requirements

  • 5+ years of software testing experience, including at least 2+ years in VoIP, voice, or real-time communication systems.
  • Strong hands-on understanding of SIP protocol, including call flows, registrations, INVITE flows, SDP, and RTP.
  • Practical experience analyzing SIP/RTP traffic.
  • Experience testing call center or CCaaS systems, including IVR flows, ACD/call routing logic, call recording, and agent states.
  • Familiarity with WebRTC technologies and real-time communication challenges.
  • Deep understanding of voice quality metrics such as latency, jitter, packet loss, echo, and MOS.
  • Solid knowledge of TCP/IP networking, NAT, firewalls, ports, and STUN/TURN.
  • Experience working in Linux environments and reading server logs.
  • Basic scripting skills in Python, JS, or TS for test tooling and log analysis.
  • Experience with REST API testing using tools such as Postman or curl.
  • Understanding of RTP media flow versus SIP signaling.
  • Ability to debug one-way audio, no audio, delayed media, and early media issues.
  • Experience testing systems that depend on timing, network conditions, and concurrency.
  • Understanding of how telephony differs from web applications in stateful, event-driven, and race-condition-heavy systems.
  • Experience with test automation using Playwright or similar tools (nice to have).
  • Experience with API automation frameworks such as pytest or REST Assured (nice to have).
  • Familiarity with performance and load tools such as k6, JMeter, or Locust (nice to have).
  • Experience simulating SIP traffic using SIPp (nice to have).
  • Experience working with PBX, SBC, or softswitch technologies such as Asterisk, FreeSWITCH, or Zoiper (nice to have).
  • Experience testing under network impairment conditions such as packet loss or delay simulation (nice to have).

Benefits

  • Comprehensive medical insurance and access to mental health programs.
  • Sports card perk for employees located in Bulgaria.
  • Bonuses and corporate gifts.
  • Free educational events and courses.
  • English classes with native speakers.
  • Strong mentorship and a supportive environment for professional development.
  • Flexible working format with remote, office-based, or hybrid options.
  • Team-building activities and a friendly workplace atmosphere.

Interested in this position?

Apply directly on the company website

Apply Now

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