Building Quality into LLMs through Testing and Observability

In the previous blog post, we explored how LLMs are changing the way we develop software and how we need to think differently about data, engineering, and architecture to cater to them. In this second part, I will explore testing, observability, and the related aspects of ethics a little further.

And when it comes to LLM-powered applications, testing is certainly not second fiddle. In fact, it could be argued that it is even more important than in traditional software development. Unlike conventional systems, where requirements and outcomes can often be precisely defined, LLM behavior is inherently probabilistic and context-dependent. This means you can’t simply test for a single correct output; you need to test across a spectrum of possible responses to ensure consistency, reliability, and safety.

Because LLM development typically involves frequent iterations, prompt adjustments, fine-tuning updates, or model retraining, the role of testing becomes critical in catching regressions. Even a small change in a training dataset, a new system prompt, or a configuration tweak can ripple through the model and alter outputs in unexpected ways. Without rigorous regression testing, it’s easy for improvements in one area to unintentionally degrade performance in another, undermining overall quality.

Automation is key here. Just as DevOps transformed traditional software with continuous integration and automated regression checks, LLM systems require automated pipelines that can quickly evaluate prompt templates, model outputs, and edge cases against defined benchmarks. This is especially true given the non-deterministic nature of LLMs, where repeated runs with the same prompt might produce subtly different results. Automated testing allows teams to run large-scale evaluations across variations, flag anomalies, and track output trends over time.

Moreover, testing LLM-powered systems must go beyond functionality to include ethical, fairness, and bias testing. Automated test harnesses can probe for harmful stereotypes, inappropriate outputs, or failures on underrepresented inputs. This ensures that as models evolve, they not only remain technically sound but also uphold the organization’s ethical and compliance commitments.

In short, testing is not just a safeguard in LLM applications; it’s a strategic enabler of quality. It helps teams maintain confidence in rapid iteration cycles, detect regressions early, and validate that models remain safe, reliable, and aligned with business goals as they evolve. Far from being a secondary consideration, testing is the backbone of sustainable and trustworthy LLM-powered development.

TDD remains

Incorporating Test-Driven Development (TDD) principles into LLM workflows is becoming increasingly important as these systems evolve rapidly through frequent iterations and fine-tuning cycles. Writing tests before integrating or modifying an LLM helps teams clarify expectations about behaviour, accuracy, tone, and compliance before the model ever generates an output. This proactive approach ensures that every change—whether a new prompt, retraining pass, or system update—is measured against clearly defined quality benchmarks.

Because LLMs are non-deterministic and dynamic by nature, TDD provides a crucial anchor of consistency. By codifying expected patterns of responses and defining pass/fail thresholds early, teams can detect drift or unintended consequences as soon as they appear. This not only strengthens regression coverage but also builds confidence that evolving models continue to align with business, ethical, and user expectations. In essence, TDD transforms testing from a reactive safeguard into a strategic design tool, ensuring that even as LLM behaviour evolves, it remains purpose-driven, verifiable, and reliable.

Testing Beyond Traditional QA

Alongside traditional TTD thinking, though, some testing requires a rethink. Conventional QA practices were designed for deterministic systems, where inputs reliably produce the same outputs. Large Language Models, however, are probabilistic; their responses can vary across runs, contexts, or even prompt phrasings. This shift demands an expanded approach to testing, one that blends automation with human judgment and continuously evolves as models and use cases change.

Golden Sets and Benchmarks

• Maintain curated test datasets with known expected outputs to validate baseline consistency.

• Use benchmarking frameworks that compare responses across model versions or prompt variations to detect regressions.

• Regularly refresh golden sets to include new business requirements, data updates, or emerging risk scenarios.

Human-in-the-Loop Evaluation

• Automated checks alone can’t measure qualities like tone, empathy, persuasiveness, or cultural appropriateness.

• Incorporate expert reviewers or domain specialists to evaluate subjective aspects—such as compliance with brand voice or adherence to regulatory standards.

• Use structured rubrics to make human scoring more consistent and scalable.

Bias and Fairness Testing

• Continuously probe outputs for harmful stereotypes, imbalanced representation, or exclusionary behavior.

• Test against demographically diverse datasets and underrepresented scenarios to catch subtle disparities.

• Implement bias dashboards to track fairness metrics over time and embed corrective feedback loops into retraining or fine-tuning cycles.

Adversarial Testing

• Design stress-test scenarios with deliberately ambiguous, misleading, or malicious prompts to evaluate robustness.

• Test for prompt injection attacks, data leakage risks, and jailbreak attempts to ensure safeguards hold under hostile conditions.

• Include edge cases (e.g., rare terminology, conflicting instructions, or multi-step reasoning tasks) to push the limits of model performance.

Continuous & Multi-Dimensional Evaluation

• Testing for LLMs is never a one-off certification. Establish continuous evaluation pipelines that run with each model update, dataset refresh, or prompt change.

• Track multi-dimensional quality metrics: factual accuracy, stability, bias/fairness, safety, latency, and cost-effectiveness.

• Use A/B testing and shadow deployments to validate new models in real-world settings before full rollout.

Testing LLM systems requires moving beyond binary pass/fail QA. It’s about measuring reliability across multiple dimensions, incorporating both automation and human judgment, and proactively probing for risks. By expanding QA practices to include golden sets, fairness probes, adversarial tests, and continuous monitoring, organizations can gain confidence that their LLM-powered applications are not just functional—but also safe, fair, and trustworthy.

Monitoring, Feedback, and Continuous Improvement

For LLM-powered applications, delivering a quality release isn’t the finish line—it’s the starting point of an ongoing cycle. Because models are probabilistic, context-sensitive, and influenced by evolving data, they can drift, degrade, or behave unpredictably over time. Sustaining reliability requires a continuous improvement mindset, backed by systematic monitoring and structured feedback loops.

Real-Time Monitoring

• Track key operational metrics like latency, uptime, and throughput to ensure performance scales under real-world usage.

• Monitor quality signals such as factual accuracy, toxicity detection, and safety flags triggered by moderation layers.

• Implement user satisfaction indicators, like thumbs up/down, completion rates, or task success rates, to detect pain points early.

Feedback Loops

• Capture user corrections, overrides, and escalations to identify where outputs fall short of expectations.

• Feed this data back into iterative fine-tuning, prompt optimization, or reinforcement learning processes to steadily improve accuracy and relevance.

• Encourage open reporting channels (e.g., inline “Report Issue” buttons) to make it easy for users to contribute to quality refinement.

Drift Detection

• Continuously monitor for data drift (when the input data changes from what the model was trained on) and concept drift (when the meaning or context of data evolves).

• Use statistical monitoring and anomaly detection to spot when the model’s responses begin diverging from expected behavior.

• Proactively plan retraining or model replacement cycles to minimize downtime or performance degradation.

Transparent Metrics

• Define clear, measurable KPIs such as factual accuracy rates, bias incidents, compliance violations, error frequencies, and resolution times.

• Make these metrics visible across the organization via dashboards, regular reporting, or automated alerts.

• Transparency builds trust, not just internally with leadership and developers, but also externally with regulators, auditors, and sometimes even end-users.

Continuous Learning Culture

• Treat monitoring and feedback as part of a living system: models are never “done,” they’re only “current.”

• Encourage teams to share lessons learned, failure cases, and success stories so improvements compound across projects.

• Foster collaboration between engineering, QA, security, and compliance teams to ensure improvement efforts stay holistic.

Unlike traditional software, LLM systems can’t be “set and forget.” They require constant observation, structured feedback loops, and proactive adaptation to sustain quality over time. By combining real-time monitoring, drift detection, and transparent KPIs with a culture of continuous learning, organizations can ensure their AI systems remain reliable, safe, and aligned with user expectations long after deployment.

Compliance, Ethics, and Trust

Finally, quality in AI isn’t only about system performance; it’s also about ethics, accountability, and compliance. LLM-powered applications shape decisions, influence behavior, and touch sensitive data, which means that ensuring trust and compliance is as important as ensuring accuracy or uptime. A system that works well but fails ethically can create legal risk, reputational damage, and long-term mistrust.

Explainability

• Users need visibility into how and why outputs are generated, especially in high-stakes domains like healthcare, finance, or HR.

• Provide source transparency when possible (e.g., citing retrieved documents in retrieval-augmented generation).

• Offer confidence scores, decision trees, or rationale summaries that help users evaluate whether to trust or validate the result.

• Explainability empowers users to make informed decisions instead of blindly accepting AI recommendations.

Auditability

• Maintain detailed logs of prompts, inputs, outputs, and model-influenced decisions for accountability.

• Support compliance reviews and incident investigations by enabling traceability across the AI lifecycle.

• Implement version control for prompts, datasets, and models, so changes can be tracked and rolled back if needed.

• Robust audit trails protect organizations in case of disputes, regulatory inquiries, or ethical challenges.

Policy Alignment

• Ensure systems comply with legal and regulatory frameworks such as GDPR (data privacy), HIPAA (healthcare), SOC 2 (security), or emerging AI-specific standards like ISO/IEC 42001.

• Go beyond minimum compliance to align with internal AI ethics guidelines and industry best practices, ensuring decisions reflect organizational values.

• Adopt risk-based frameworks for assessing AI systems (e.g., the EU AI Act’s risk tiers) and enforce controls proportionate to the level of potential harm.

• This creates resilience not only against regulatory penalties but also against reputational risk.

Human Oversight

• Even the best-architected AI systems benefit from human-in-the-loop safeguards for sensitive or high-impact use cases.

• Define clear escalation paths for when model outputs are uncertain, unsafe, or out of scope.

• Human oversight ensures ethical alignment and provides accountability in ways machines cannot fully replicate.

Quality in AI must be multi-dimensional: technical reliability is only the foundation. True quality also requires systems to be explainable, auditable, and aligned with both external regulations and internal ethics policies. This ensures that AI applications not only perform well but also remain trustworthy, compliant, and socially responsible over time.

Building Reliability in the Age of AI

LLM-powered applications represent one of the most exciting frontiers in software development—but they demand new approaches to quality. By embedding safeguards into data, design, architecture, testing, monitoring, and governance, organizations can move beyond experimentation and toward reliable, trustworthy AI systems.

The shift is clear: building quality in LLM systems is not about perfection; it’s about resilience, transparency, and continuous learning. Those who master this balance will not only reduce risk but also unlock AI’s transformative potential with confidence.