Stress-Testing Your Startup: A Practical Guide to Best, Base, and Bear Cases

Real scenario planning starts from a different premise. Your business doesn’t scale or contract along a single line. It shifts across dozens of interconnected decisions at once, and a model that only flexes revenue misses all of them. The founders who get this right walk into board meetings and fundraising conversations with something much more useful than an optimistic number and a pessimistic one. They walk in with three fully reasoned versions of their company’s future, each one built from the ground up.

Here’s how to build that.

Why ‘Best, Base, Bear’ Is a Framework, Not a Model

The instinct to treat scenarios as a percentage slider comes from a reasonable place. Revenue is the number everyone watches, so it feels like the natural lever to pull. But a startup’s best case and worst case aren’t just different revenue outcomes. They’re different operating realities, and each one carries its own decisions about hiring pace, burn rate, go-to-market spend, and product roadmap.

Consider what actually changes between a bull and a bear year. In the bull case, you’re probably hiring ahead of demand, increasing paid acquisition spend because it’s paying back faster than expected, and pulling roadmap items forward to capture momentum. In the bear case, none of that holds. Hiring slows or freezes. Paid spend gets cut because the payback math no longer works. The roadmap narrows to whatever protects your core retention.

A model that only moves the revenue line captures none of this. It tells you what the top of your P&L might look like without telling you what decisions got you there or what decisions you’d need to make in response. Scenario planning, done properly, is a framework for operating differently under different conditions, not a spreadsheet trick for generating three numbers to put on a slide.

This is also the piece that separates a founder-built model from one built with an experienced finance partner in the room. An outsourced accounting team that’s built dozens of these models across different business types knows which operating levers actually move in each scenario, and which ones founders tend to overlook until it’s too late to pull them.

Building Your Scenarios from First Principles

Once you accept that scenarios are operating realities and not revenue adjustments, the next question is where to start. The answer is almost never “adjust everything.” Most startups have three to five variables that drive the overwhelming majority of the variance in their model. Everything else is noise by comparison.

For a B2B SaaS company, those variables are often new logo growth, net revenue retention, average sales cycle length, and average contract value. For a marketplace business, they might be supply-side liquidity, take rate, and repeat purchase rate. The specific variables differ by business model, but the exercise is the same: find the handful of inputs that, if they moved, would meaningfully change your outcome, and build your scenarios around those.

The critical discipline here is defining each variable independently for each scenario rather than adjusting it by a fixed percentage off your base case. If your base case assumes an 18% net retention rate and a 90-day sales cycle, your bear case shouldn’t just knock retention down by some arbitrary amount. It should ask a harder question: if the market tightens and buyers get more cautious, what does that actually do to your sales cycle, and does that change also drag on retention because expansion deals slow down too? The variables in a real model talk to each other. A percentage-adjustment model treats them as if they don’t.

This is the part of scenario planning that takes the most time and the most judgment, and it’s also where a fractional CFO earns their keep. Getting the assumptions right requires both modeling fluency and enough pattern recognition across other companies to know which variables are plausible and which ones are wishful thinking dressed up as a forecast.

The Three Scenario Models in Practice

With your key variables identified, the actual construction of bull, base, and bear cases gets more concrete.

The bull case should answer a specific question: what does outperformance actually require, and what are the operating implications if you get there? This isn’t “everything goes slightly better.” It’s a defined set of conditions, like a flagship account expanding faster than expected or a new channel outperforming its early signals, paired with what you’d do operationally if those conditions held. Would you accelerate hiring? Increase spend in the channel that’s working? The bull case is only useful if it comes with a plan for what you’d do with the upside, not just a bigger number at the bottom of the page.

The base case is the one that should get the most scrutiny, because it’s the one boards and investors will hold you to. It needs to be genuinely probable given your current pipeline, your recent conversion trends, and the deals you can already see forming. A base case built on hope rather than trendlines is the fastest way to lose credibility with a board three quarters in.

The bear case is where founders tend to pull their punches, and it’s the one that matters most. A good bear case asks what happens if one major assumption breaks. Not everything going wrong at once, but the single most load-bearing assumption in your model failing. If your largest customer doesn’t renew. If your sales cycle doubles because budgets tighten. If your best channel stops working. The question isn’t just what your revenue looks like in that world. It’s whether you survive it, and what you’d need to do differently to make sure you do.

This is the exercise Rooled’s fractional CFOs run with founders on a recurring basis, because a bear case that’s never been stress-tested against your real numbers isn’t a bear case. It’s a guess with better formatting.

Connecting Scenarios to Runway and Decisions

A scenario model that lives in a spreadsheet and never touches a decision isn’t doing its job. The real value shows up when you calculate runway under each case and use the differences to set decision gates ahead of time, before you’re under pressure to make the call in the moment.

Runway looks meaningfully different across your three scenarios, and that difference should tell you something concrete. If your bear case runway drops below twelve months, that’s not just a data point. It’s a trigger. The founders who navigate downturns well are the ones who decided in advance what they’d do if certain thresholds got crossed, rather than debating it in real time while the number is already moving against them.

This is where decision gates come in: “If we’re tracking to the bear case by the end of Q3, we pull the Series B process forward” is a much stronger plan than “we’ll figure it out if things slow down.” Setting these gates ahead of time takes the emotion out of a decision that’s much harder to make clearly once cash is actually tight. It also gives your team and your board a shared understanding of what triggers a change in direction, so nobody is caught off guard when you pull that trigger.

Building this kind of decision framework alongside a scenario model is standard practice in Rooled’s CFO advisory work, largely because it’s the piece that turns a modeling exercise into something that actually protects the business.

Presenting Scenarios to Your Board

All of this work is wasted if it shows up in a board deck as a single number with a footnote. Boards that have seen a lot of these decks aren’t looking for the illusion of certainty. They’re looking for evidence that you understand the range of outcomes in front of you and have already thought through how you’d respond to each one.

The strongest scenario-based board decks tell a narrative rather than presenting three columns of numbers side by side. Start with what’s actually happening in the business right now and where that puts you relative to your base case. Walk through what would need to be true for the bull case to materialize, and whether you’re seeing early signs of it. Then walk through the bear case with the same seriousness, including the specific triggers that would move you into it and the decisions you’ve already agreed you’d make in response.

Presented this way, scenarios stop being a defensive exercise and start doing what they’re actually good for: driving a real conversation with your board about where the business is headed and what support you need to get there, rather than a report-out where the board just nods at whatever number you’ve landed on.

Rooled builds scenario models like this as a standard deliverable for the founders we work with, from identifying the right variables through to the board-ready version of the story. If you want to see what one looks like built around your own numbers, let’s talk.