The old vendor’s contract ends on Friday. The new vendor starts on Monday. The release deadline hasn’t moved – and for a business delivering a critical platform to customers, production outages are not an option. In sectors like finance, healthcare or large-scale cloud-based services, even a short disruption can mean missed client commitments, reputational damage and costly remediations.

What happens during the transition can decide whether your testing stays smooth… or falls apart. This post dives into the testing handover process during a vendor transition, and how to get it right.

Testing Handover in a Vendor Transition

In a vendor transition, testing handover is the structured transfer of all QA responsibilities, assets, environments, and project knowledge from the outgoing testing partner to the incoming one – without losing quality or delivery speed.

Vendor changes in consulting engagements happen for many reasons: cost adjustments, performance concerns, contract expirations or scaling needs. Whatever the reason, the goal remains the same: continuity – so testing doesn’t skip a beat.

Why Proper Handover Matters

If the process isn’t handled carefully, you can expect trouble. Some common risks include:

• Knowledge loss – beyond product quirks, testing shortcuts, and known risks, transitions risk losing the broader domain knowledge and project context. Over time, teams build up an implicit understanding of how different systems interact and how the bigger picture fits together – valuable insight that can disappear with the outgoing team.
• Tool access gaps – the incoming vendor can’t start testing due to missing credentials or environment setup.
• Missed defects – untested areas can slip through when no one knew they existed, but the risk is broader than that. Without visibility into what has been tested, how it was tested, and the level of confidence in those results, it’s easy for gaps to remain hidden – leading to defects surfacing later in production.
• Blame loops – old and new vendors pointing fingers at each other when defects and delays arise.

Vendor-focused Handover Checklist

From the moment the project’s end date is confirmed – whether it is specified as a particular week or a fixed date – you should plan the handover steps to fit within the remaining time. One factor that can strongly influence how the handover unfolds is the level of client stakeholder engagement. If they remain passive, the outgoing vendor may end up driving all conversations and decisions, which can increase the risk of gaps or misalignment.

1. Preparation – by the outgoing vendor

• Compile updated test documentation – test plans, test cases, scripts, evidence, and bug reports.
• Provide test data and environment configurations.
• Document the current release cycle status – what’s tested, pending, or blocked.
• List all ongoing defects and their resolution statuses.

2. Knowledge Transfer – joint sessions

• Walk through test coverage, known product risks, and historical problem areas.
• Demo test automation frameworks and how to execute them.
• Explain communication channels, escalation paths, and reporting formats.
• Provide working tool credentials – Jira, test case management tools, automation repositories, CI/CD pipeline access.

3. Transition Sign-Off – client-led

• Confirm the incoming vendor can execute tests independently.
• Agree on handover completion criteria (e.g.: “Incoming vendor successfully executed smoke tests”).
• Finalise ownership of pending defects and tasks.

Best Practices for Vendor Transitions

Smooth handovers don’t happen by chance — they’re the result of clear planning, deliberate overlap, and strong communication. These best practices capture what works in real vendor transitions, helping both outgoing and incoming teams keep testing steady while the organisational gears shift.

• Start early – overlap old and new vendors for at least one sprint if possible
• Use a formal checklist to avoid “oh I forgot to mention this” moments
• Record sessions or write summaries – vendors may be in different time zones
• Assign a transition lead – typically one person appointed by the client to oversee and confirm completion, although it’s common and beneficial for each party to have their own lead
• Document ‘tribal knowledge’ – known quirks, fragile integrations, workarounds
• Balance project-specific knowledge with general skill development – prioritise unique systems, workflows and context of the project over generic upskilling that doesn’t directly support delivery
• Proactively escalate risks – acknowledge challenges faced by all teams with open, empathetic communication

A Real-World Case

During a recent engagement, Scott Logic acted as the development vendor for a fintech firm. The project was greenfield—building the platform entirely from scratch—bringing together multiple new systems and integrations with no existing framework to build on. I joined for the final four and a half months as a Test Engineer.

As the project neared its end, the Scott Logic testing team approached the testing handover for the incoming vendor with precision from the moment the end date was set. A dedicated testing handover date was declared before the official contract end, helping to clearly define where to stop testing and creating space to support the incoming team with any handover issues during the last week. Early engagement with stakeholders, documenting handover topics in Confluence – a team knowledge-sharing platform allowing teams to create, organise and share information in a central, searchable space – and setting clear expectations ensured a smooth transition.

Delivery work continued alongside gradual transition tasks such as cleaning up Playwright test automation code, updating README files, documenting coverage gaps, and producing troubleshooting guides for test user management, authentication failures, and end-to-end (E2E) testing flows. A key target was keeping the nightly E2E pipeline green, achieved by delegating failing test fixes to developers while testers focused on knowledge transfer. Recorded walkthroughs and slide decks ensured no critical knowledge was lost.

Beyond documentation and handover calls, Scott Logic testers identified some key cultural and communication dynamics that affected knowledge transfer sessions. Initially, the incoming vendor’s testers expressed agreement during discussions but hesitated to openly share uncertainties or knowledge gaps, creating a risk of misunderstandings about their actual readiness and learning needs. Recognising this, the team adjusted the approach: the Scott Logic transition lead, along with testers based on availability, joined daily stand-ups and knowledge transfer calls with the incoming team. Every session began with light warm-up chats to create a friendly, safe atmosphere, which helped the new testers feel more comfortable and gradually become more active, asking more questions.

When it became clear the client and incoming consultancy lacked time to complete the onboarding process, the Scott Logic team adapted. The transition lead encouraged targeted questions, drew clear lines between handover and upskilling, and still directed newcomers to useful resources. On the final week, daily stand-ups brought both vendors together for real-time Q&A, while a short shadowing period with optional drop-ins balanced support with closure.

We also escalated late-stage risks to senior stakeholders, warning that minimal technical engagement from the incoming vendor and client could threaten platform stability. We recognised the difficult circumstances the incoming team faced and framed these discussions with empathy — focusing on solutions and support rather than criticism. This wasn’t just self-protection — it was proactive risk management to safeguard long-term success. The result was a transition that was efficient, adaptable, and accountable, even under tight deadlines.

Closing Takeaway

The handover in this project proved that vendor transitions don’t have to result in disruption. By setting clear targets like a green nightly E2E pipeline, structuring documentation, creating space for real-time Q&A between old and new teams, and being willing to adapt when onboarding time was limited, the team kept quality intact and risks visible.

In vendor transitions, testing handover is the bridge between old and new. Build it deliberately, walk both teams across together, and you can maintain stability — even under tight deadlines and shifting circumstances.