How to write a take-home tech test that candidates actually want to do
Most take-home tests fail because of setup friction, unclear briefs, or disrespecting people's time. This is how I designed one that candidates thank us for.
I'm Warren de Leon, a Software Engineering Manager at Hargreaves Lansdown, where I've recently joined to lead engineering teams in one of the UK's largest investment platforms.
Before HL, I spent over two years at Sky managing multiple engineering squads delivering mobile and web products used by millions of customers. I led teams within Sky's SAFe-based organisation, overseeing 10+ engineers across permanent, contract, and early-career roles.
My technical roots are in React Native. Since 2017, I've built and led teams delivering apps for Sky, Shell, BP, and Chelsea FC, among others. That hands-on experience with mobile architecture, CI/CD pipelines, and cross-platform delivery is what I bring to my leadership: I manage engineers with the context of someone who's been in the codebase.
Born and raised in Barcelona with Filipino heritage, I started my career there as a full stack developer and taught Android development across Europe as part of an international employability programme. Moving to the UK in 2016 added another perspective. That multicultural background, growing up between Catalan, Spanish, and Filipino cultures before building a career in London, shaped how I think about teams, communication, and inclusion.
My focus is on people: coaching, progression, honest feedback, and building squads where engineers do their best work. I've guided associate engineers from graduate programmes into confident, independent contributors, and I take that responsibility seriously.
When I'm not managing, I'm still building. This website is an Astro static site I built myself. My personal portfolio app is a React Native project with 75%+ test coverage, five-language internationalisation, and Detox E2E testing. I stay close to the craft because I believe the best engineering leaders never fully leave it.
Engineering Manager — Mobile Platform
Mar 2026 - Present
Leading the Mobile Platform squad within the UCX-Core tribe, part of Hargreaves Lansdown's Digital Product Engineering division. My team is building HL's new React Native mobile app from scratch, replacing the existing native iOS and Android apps. We own the platform architecture that every mobile team at HL ships through.
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Most take-home tests fail because of setup friction, unclear briefs, or disrespecting people's time. This is how I designed one that candidates thank us for.
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