What to Test First in a New Codebase: My ExperimentWhat to Test First in a New Codebase: My Experiment

When it came to deciding what to test first in a new codebase, I froze. It was last Tuesday, 9:17am, coffee going cold on my Denver apartment desk. I'd just cloned this indie todo app repo, clean, no test suite, screaming 'ship it fast', but my gut twisted from old scars.

You know that chest-tight feeling? The one where you're the QA lead again, staring at blank screens before a demo. I'd paged myself at 3am too many times because we skipped risk assessment on signup flows. This time, I wanted a real test strategy, no more guessing.

So I set up the experiment. Picked three paths: core user flows first, then unit testing basics, integration testing last. Tracked test coverage, bugs found, time spent. Hands shaky hitting run on CI, half-expecting the old spiral of flaky failures.

The dilemma hit hard. Dive into codebase analysis and analyzing existing tests (spoiler: there were none)? Or jump to test case prioritization on expected behaviors and edge cases? My jaw clenched thinking of past refactors that nuked code quality. This was personal.

What to Test First in a New Codebase?#

When it came to deciding what to test first in a new codebase, I found myself at a crossroads, unsure of how to prioritize my efforts. It was a moment that sparked a curious experiment, one that would challenge my long-held beliefs about testing. You know that gut punch? Staring at a blank repo on a Tuesday at 9:17am in my Denver apartment, coffee going cold, heart racing because I've shipped bugs before and paid the price.

This was a fresh React app for a side project. No tests. Zero. Just clean code begging for a test strategy. My palms sweated as I thought about code quality from day one.

Past nightmares flashed back. That startup where we skipped unit testing on auth flows? $200K lost in a weekend. Now, here I was again, facing the same choice on test coverage.

“

Staring at a blank repo on a Tuesday at 9:17am, coffee going cold, heart racing because I've shipped bugs before and paid the price.

— Sam

Should I dive into unit testing for every component? Or chase edge cases in user flows right away? My mind spun. I needed prioritizing tests effectively, but doubt clawed at me.

I remembered arguing with PMs. 'Just write more tests,' they'd say. But in a new codebase, that's a trap. Without a solid test strategy for new projects, you're building on sand.

Chest tight, I opened VS Code. Cursor blinked mockingly. QA testing insights from six years screamed: start small or drown in maintenance.

I paced my living room. Denver skyline mocked me through the window. What if I botch this test coverage and kill momentum? Fear hit hard.

Unit testing feels safe. Mock dependencies, cover functions fast. But edge cases? They lurk in integrations, waiting to bite.

I grabbed my notebook. Jotted pros, cons. Hands shook slightly. This wasn't just code. It was my shot at better code quality.

Flash to old job. Tests passed locally, failed CI. No one cared about edge cases then. Now, I vowed different.

That crossroads feeling? It's universal for solo devs. No QA team. Just you vs. the blank slate. My experiment started there.

Setting Up the Experiment: What to Test First in a New Codebase#

I sat in my Denver apartment on a rainy Tuesday. Laptop screen glow. Coffee cold at 2:17pm. Time to pick a victim for this test strategy madness.

You know that feeling. Stomach drops. Too many GitHub tabs open. I needed a new codebase that screamed 'test me first or regret it.'

“

Picking the wrong project felt like dating someone with 47 exes still texting. Disaster waiting.

— Sam

I scrolled my repos. One stood out: 'QuickAuth,' a half-built auth app from last year. Forgot it existed. Perfect for pretending it was brand new.

First, codebase analysis. 1,247 lines of React and Node. No test suite. Zero coverage. My heart raced, pure chaos ahead.

I laughed out loud. Alone. 'Sam, you idiot, this has login flows begging for integration testing.' But humor hid the dread.

Plan hit me. Week one: unit testing core utils. Then integration testing APIs. Track time spent on refactoring and debugging.

Why this one? Risk assessment screamed high. User signup. Token storage. Edge cases like expired sessions. No self-explanatory code anywhere.

Internal voice yelled: 'Don't chicken out.' I cloned it local. Ran 'npm start.' Page loaded. Blank slate stared back.

Test strategy for new projects? Start small. But prioritizing tests effectively meant hitting user flows first. Not utils.

I jotted notes. 'Day 1: Mock login API. Day 2: Full integration testing.' Fingers itched for code. But paused.

That pause? big deal. QA testing insights from past scars. Digesting the tests, wait, there were none. Digest the voids.

Refactoring loomed. Code smelled. Dead components everywhere. Debugging without tests? Nightmare fuel. I shuddered, jaw tight.

Navigating codebase testing solo. No team. Just me, Mountain Dew, and fear. But excitement bubbled too. Contradiction, right?

Final pick locked. QuickAuth it was. Commit: 'Experiment start: What to test first in a new codebase.' Push. No turning back.

Hands shook a bit. Not from cold. From knowing one bad test suite could break me. Humor faded. Reality hit.

Week One: What to Test First in a New Codebase#

I picked a fresh Next.js project. A simple task manager app. No tests yet. Heart raced as I stared at the blank test folder on Monday at 9:42am.

First, I did a risk assessment. Focused on auth flow and task CRUD. These hit users hardest if broken. Ignored styling tweaks for now.

Test case prioritization became my guide. I listed ten cases. Picked top three: login success, failed login, create task. That's prioritizing tests effectively.

Set up test automation with Jest for unit testing. Then Playwright for integration testing. Felt good. Until it didn't.

Integrated into my development workflow. Wrote a login test TDD style. Ran it. Green. Pushed to GitHub for continuous integration.

CI failed at 11:17am Wednesday. Mocking broke on env vars. My hands got sweaty. Stomach dropped like I'd shipped a prod bug.

Debugged for 47 minutes. Fixed mocking deps. Tests passed. But resentment built. Why fight the tools on day three?

Initial results? Two bugs caught early. Login redirect glitch. Task dup on refresh. QA testing insights: detecting issues early saves weekends.

Test coverage hit 23% by Friday. Not bad for week one. But maintenance nagged. Refactoring auth renamed a selector. One test flaked.

Analyzed existing tests? None yet. So I digested what I'd built. Expected behaviors and edge cases emerged. Like empty task lists.

Chest tight each run. Hope mixed with dread. This test strategy for new projects? Promising. But challenges exposed gaps in my plan.

Navigating codebase testing solo hurts. No team to blame. Just me, the code, and that nagging doubt at 4pm Fridays.

The Tiny Test That Uncovered Deep Flaws#

It was Thursday, 2:17 pm. Denver sun beat through my window. I sipped cold coffee, staring at my screen.

Week two of my experiment on what to test first in a new codebase. I'd picked a simple user signup flow. Felt safe. Harmless.

Started with analyzing existing tests. The suite was sparse. Unit tests mocked APIs poorly. No coverage for real flows.

“

You think it's just a quick check. Then it rips open the code's underbelly.

— Sam

I leaned into test-driven development. Wrote one tiny integration test. Mocked the email service. Expected a success redirect.

Ran it. Green at first. Then I pushed an edge case: invalid email format. Boom. Server crashed with null pointer.

My stomach dropped. Hands froze on keyboard. This wasn't a flaky test. This was core logic rotting.

Code wasn't self-explanatory code. Comments lied. Functions hid silent failures. Refactoring would break it all.

Internal voice screamed: 'How did this ship?' Jaw clenched. Fingers itched to rewrite. But this proved my point.

That minor test flipped my test strategy for new projects. Prioritizing tests effectively meant hitting risks first. Not the shiny paths.

Called my co-founder on Slack. 'Dude, this signup test just exposed a cascade failure.' He typed back: 'Rewrite or die.'

Spent the next hour in debugging hell. Traced mocks to real API calls. Found unhandled errors in three modules.

Eyes burned from staring. Coffee turned bitter. Pride mixed with nausea. I'd dodged a production fire.

This gave QA testing insights. Navigating codebase testing starts small. But small reveals the cracks. Always.

The Results Hit Me Like a Deep Breath#

I sat in my Denver apartment on Friday evening. Spreadsheet open. Numbers stared back. My chest loosened for the first time in weeks.

This experiment on what to test first in a new codebase changed everything. Previous projects? Chaos. I'd chase bugs in production. Heart racing at 2am pings.

“

Relief isn't quiet. It's your shoulders dropping. Breath you forgot you were holding.

— Sam

First metric: bugs found. Old project took 14 weeks to ship. Caught 7 bugs post-deploy. Cost us $12K in hotfixes. Stomach still knots thinking about it.

How? Started with digesting the tests. Existing ones showed weak spots. Then locating unit tests for core flows. Integration testing filled the gaps.

We focused on test strategy for new projects. Hit user auth, payments first. Mocking external APIs kept it fast. Detecting issues early saved our asses.

Time saved? Huge. Past suites ran 42 minutes. Flaky as hell. Maintenance ate 15 hours weekly. I'd dread Mondays. Jaw clenched over coffee.

Prioritizing tests effectively meant no more firefighting. Code quality soared. Test coverage hit 78% on critical paths. Without the bloat.

One moment sealed it. Thursday, 4:17pm. CI green. No reds. I leaned back. Laughed out loud. Alone. Tears pricked my eyes.

Compared to last project: 28 bugs total, half post-launch. Now? 23 pre-deploy. Zero escapes. Codebase analysis paid off big.

Navigating codebase testing felt natural now. Test-driven development for new features. Self-explanatory code emerged. Team morale? Skyrocketed.

Relief lingered into Saturday. Walked the dog. No phone checks. First time in months. Hope flickered. Real, not hype.

What to Test First in a New Codebase: Who Benefits and My Next Experiment#

I sat in my Denver kitchen last Tuesday. Coffee gone cold. Staring at my notebook from the experiment. My chest tightened reliving the relief of catching that edge case early.

Solo devs get this most. You're coding alone. Shipping fast with AI tools like Cursor. No test suite means one bug tanks your launch. This test strategy for new projects changed that for me.

“

If your codebase feels like a black box, start with user flows. Not every unit test.

— Sam

Startup founders without QA teams? You're it. PM, dev, tester. I was there. $200K lost on a bad signup once. Prioritizing tests effectively would've saved us.

QA engineers burned out on maintenance. You've fixed selectors at 3am. My findings cut that noise. Focus on integration testing first. Then refactor safely.

Analyzing existing tests showed me the gaps. Digesting the tests first. Locating unit tests next to source files. It's QA testing insights you can use today.

Navigating codebase testing still scares me sometimes. But now I know: user-critical paths first. Mocking for speed. Test-driven development where it counts.

What we built at yalitest came from this pain. Vision AI for those first tests. Plain English. Self-healing. It let me run this experiment without flakiness.

Next experiment? Mobile testing on a React Native side project. iOS and Android quirks await. Heart races thinking about Appium flakes. But I'll pick flows first. Same strategy.

You're probably wondering if this works for you. Stomach drops if you're on the fence. I get it. Feels vulnerable starting tests in a fresh codebase.

Truth? I'm still tweaking. Last deploy, a sneaky edge case slipped. Jaw clenched at 11pm. But fewer fires now. That's the win.

Grab your coffee. Open that new repo. Feel the knot loosen as one test passes. That's the quiet hope I chase.