In today's complex world, governments are increasingly seeking innovative approaches to tackle pressing social issues. The concept of ‘Test and Learn’ has become a central element in discussions around effective governance and public sector reform. This approach, which emphasises iterative development and learning from real-world implementation, is recognised as a valuable methodology for navigating uncertainty and improving outcomes. There's a growing focus on the need for agility, piloting new programmes, and scaling what works in policymaking. But what does ‘Test and Learn’ truly mean in practice, especially when addressing an issue as complex and urgent as homelessness?  

Understanding 'Test and Learn' 

The recent Nesta and BIT report, Test and Learn: A Playbook for Mission-Driven Government, provides a valuable framework for understanding this approach. It defines ‘test and learn’ as 

‘an iterative approach to public policy and service development that starts from the ground up-policy is shaped by practice, not the other way around’. 

This represents a shift away from traditional, top-down policymaking, instead embracing a cyclical process of closely intertwining policy design, delivery, and testing. The approach draws on a range of methodologies, including design thinking, behavioural science, and rigorous evaluation, to adapt and improve policies and programmes based on evidence.

The report highlights several key building blocks for effective Test and Learn:

• Iterative development: Policy and service design is not a one-off process but an ongoing cycle of development and refinement.  
• Learning loops: Assumptions are tested early, and feedback from implementation is used to inform subsequent iterations. This is the engine of the iterative process.  
• Shaping conditions for success: Creating the right environment for Test and Learn to thrive, including fostering collaboration, empowering frontline actors, and building trust. 

Our own experience of helping the government to introduce the What Works or Test and Learn supports how these building blocks provide a valuable foundation. It also suggests that getting it right is difficult and requires consideration of a number of things upfront, especially when addressing complex social issues like homelessness. A crucial element, often missing in initial applications of Test and Learn, is a fundamental commitment to systems thinking.

This is the ability to see the bigger picture. Homelessness isn't a straightforward issue with simple causes and solutions. It is a complex issue rooted in a web of interconnected factors, including poverty, lack of affordable housing, health inequalities, and systemic failures in support systems. A systems thinking approach is therefore crucial to move beyond treating symptoms and towards addressing root causes.

The challenge of complexity: why homelessness demands a more complete framework 

While Nesta's framework is invaluable, our experience at the Centre suggests that tackling an issue as complex and multifaceted as homelessness requires incorporating systems thinking and other key dimensions to create a more comprehensive and robust definition of ‘true’ Test and Learn. It's a common refrain: ‘Homelessness isn't rocket science, so why can't we solve it?’ But the reality is, homelessness is far more intricate than sending a rocket to the moon.

Rocket science, while incredibly complicated, deals with a system that is ultimately predictable. The equations of planetary motion have been known for centuries, and have been verified empirically repeatedly. No 'laws' of social science are, or ever could be, similarly compelling. Getting a rocket to the moon may be a complicated problem but is not a complex one... Complex problems like homelessness are defined by the fact that an action in one part of the system can have unpredictable consequences in other parts, and no single intervention can solve it.... Think of obesity – gastric bands can work for individuals, but they cannot solve obesity at societal level.

To truly make progress in preventing and ending homelessness, we believe the Test and Learn approach is strengthened by incorporating Nesta's building blocks and the following essential pillars, which we propose as critical additions to create a more comprehensive definition of ‘true’ Test and Learn:

• Systems thinking: understanding - positive and negative - drivers at local, regional and national levels
• Enhancing data and evidence infrastructure: building a foundation for informed action, accountability and impact
• Implementation and behaviour change support: ensuring accountability and sustainability

These additions are designed to complement and build upon existing frameworks, recognising the unique challenges posed by complex social problems.

1. Systems thinking: understanding - positive and negative - drivers at local, regional and national levels

Unlike common opinion, homelessness is not a linear issue with simple causes and solutions. Just like the gastric bands example, even if you find a solution that delivers results for an individual or family, it may bring you no closer to solving the issue at a population level. 

For example, Housing First can be transformative for individuals, but if it becomes the sole focus—without corresponding work on prevention, housing supply, and wider system reform—it risks being no more than mopping water off the floor while the tap is still running. We have seen this dynamic play out in places like Salt Lake City and in past UK government efforts that focused primarily on rough sleeping: progress in one area was not sustained because upstream drivers and interdependencies went unaddressed.

This is why, when we launched the Centre, the first step was to create the SHARE framework to guide our efforts as a What Works Centre. It helps us ask the right questions, prioritise which part of the system to address at any given time, and anticipate potential unintended consequences of interventions. It's also why we are so pleased to be supporting MHCLG to undertake the first-ever systems-wide evaluation of the homelessness and rough sleeping system. A systems thinking approach is crucial for understanding the complexities of homelessness and designing effective government policies, programmes and interventions.

2. Enhancing data and evidence infrastructure: building a foundation for informed action

Reliable evidence and actionable data are the cornerstones of effective homelessness prevention. Without a robust data and evidence infrastructure, it's impossible to accurately assess the scale of the problem, identify effective solutions, or track progress over time. 

Our work with MHCLG on the first wave of Test and Learn trials, though small in scale, is allowing us to explore a variety of interventions and test feasibility before scaling. The funding covers both trials and direct interventions, creating early learning loops. However, future iterations need greater investment to run a much larger portfolio of prevention specific trials in parallel across different contexts, underpinned by the right data infrastructure and user-friendly knowledge platforms. These should not only share evidence but also map service models and collate case studies, enabling local and national actors to quickly identify, adapt, and apply what works.

3. Implementation and behaviour change support 

Even the most robust evidence and well-designed interventions will fail if they are not implemented effectively. Implementation requires more than just technical knowledge; it requires behaviour change at multiple levels, from frontline workers to organisational leaders. Embedding a culture of self-sufficiency and continuous improvement is essential for driving lasting change.

We work with national and local governments to help them establish clear frameworks for action, shared goals, and accountability, ensuring that all stakeholders are working towards a common vision. We are also building a movement for change that extends beyond the homelessness sector, engaging businesses, journalists, and other parts of society. Ending homelessness requires a collective effort—by forging strategic relationships, we can amplify impact and create a broader societal commitment to prevention.

Towards an effective application of Test and Learn

By grounding our approach in these interconnected pillars, we believe we can drive a more effective and sustainable prevention response, ultimately creating a future where homelessness is rare, brief, and non-recurring. This requires a long-term commitment to systems change, evidence-informed action, and collaborative partnerships across all sectors of society. 

Our work is contributing to a more robust and effective application of the Test and Learn approach, an approach that, when deployed deliberately and methodically by government, has the power to transform how we address homelessness and create lasting social change.

• Ligia Teixeira is Founding Chief Executive of the Centre for Homelessness Impact

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