--- title: "Build vs Buy for Test Automation: What an In-House Suite Actually Costs" description: "A cost model for an in-house end-to-end suite: 625 tests, $887,000 a year, and 62% of it spent investigating failures rather than writing tests." canonical: "https://momentic.ai/blog/build-vs-buy-test-automation" last-updated: "2026-09-01T22:34:45Z" --- # Build vs Buy for Test Automation: What an In-House Suite Actually Costs URL: https://momentic.ai/blog/build-vs-buy-test-automation [blog](/blog) [/ resources](/blog/category/resources) / build-vs-buy-test-automation Resources A cost model for an in-house end-to-end suite: 625 tests, $887,000 a year, and 62% of it spent investigating failures rather than writing tests. Wei-Wei Wu CEO, Momentic Building an end-to-end suite got cheap in the part everyone measures. A coding agent writes a test in minutes that used to take an afternoon. So the build side of the argument now sounds obvious: the framework is free, the agent is fast, and a vendor is a line item. The bill does not arrive there. It arrives in the year after, and the largest item in it is not writing tests. ## A cost model for an in-house suite The scenario below is a 25-developer team, 80% coverage of critical flows, one run a day. You can move every input on the calculator. | Cost | A year | Share | | --- | --- | --- | | Investigating failures | $548,000 | 62% | | Writing the tests | $188,000 | 21% | | Model inference | $143,000 | 16% | | Runners and CI | $8,000 | under 1% | | Total | $887,000 | | That is 625 tests, 162,500 test runs a year, and 2,438 failures to investigate at 1.5 hours each. The 1.5% daily failure rate is the flaky-result rate Google published, not a number chosen to make the case. [Move every input yourself](/comparison/momentic-vs-build-your-own). ## The line item nobody puts in the plan Writing tests is 21% of the bill, and a coding agent is already cutting it. Investigating failures is 62%, and an agent does not cut it by itself, because the work is a judgment: is this a real defect, a changed selector, or a slow runner? Somebody senior enough to answer that reads the failure. Do that 2,438 times a year and it is three full-time engineers. Runners cost under 1%, which is why the "it's just CI minutes" version of the build case is arguing about the wrong line. The plan almost always counts the framework, the runner and the agent, and almost never counts the engineer who investigates Monday's failed run. ## Can a coding agent maintain the suite? For a stretch, yes. An agent repairs a broken selector well, and it writes the replacement test faster than a person. Where it stops: an agent that repairs the failure it is shown can turn a real defect into a passing test. Deciding which failures deserve a repair, and which deserve a bug, is the expensive half, and it is the half that does not automate on its own. An agent also does not own the emulator fleet, the browser fleet, the retry policy or the quarantine list. ## What you are actually buying - The triage, not the authoring. Failures arrive classified, and a locator that moved is repaired during the run, not by an engineer on Monday. - Ownership of the tests stays with you. Steps are plain-English YAML in your own repository, reviewed in pull requests. The buy decision does not hand your suite to a vendor's workspace. - Infrastructure billed on usage: hosted browsers, emulators and simulators, running in parallel, with nothing to operate. - One suite across web, iOS and Android, rather than three frameworks and three fleets. ## When building still makes sense - Your product is a handful of critical flows and the suite is small enough that a failure a week is a five-minute read. - You have a hard constraint no vendor meets: an air-gapped network, a regulated environment, or hardware only you own. - Testing infrastructure is your product, or it is close enough to it that the expertise is an asset rather than a cost. - You already have a team that runs the fleet well, and the marginal cost of the next suite on it is near zero. If two of those are true, build, and the calculator will say so. ## How to decide in an afternoon Use the [calculator page](/comparison/momentic-vs-build-your-own) to test the model with your own failure count. Then compare the result with the [pricing page](/pricing), or [talk to sales](/sales) for a walkthrough. ## Build vs buy, answered. What does it cost to maintain an in-house Playwright suite? For a 25-developer team at 80% coverage of critical flows, about $887,000 a year, of which $548,000 is engineer time spent investigating failures. That assumes 625 tests, one run a day, a 1.5% daily failure rate, 1.5 hours to investigate each failure, and $150 an hour fully loaded. Runners are under 1% of it. What are the hidden costs of building test automation? Failure triage first, at 62% of the total in that model. Then the parts that never reach the plan: the fleet, the retry policy, the quarantine list, the flake that returns after a fix, and the second engineer pulled into a failure the first one could not classify. The framework and the CI minutes, which the plan does count, are the smallest items. Can a coding agent maintain a test suite long term? It can write and repair tests well. It cannot decide on its own whether a failure is a defect or a changed UI, and an agent pointed at a failing run turns a real defect into a passing test. It also does not own the browsers, the emulators or the retry policy. Long term, the agent lowers the authoring cost and leaves the triage cost where it was. When is buying a test platform cheaper than building one? When your failure count, not your test count, is large enough that triage dominates. Count the failures your suite produces in two weeks and multiply by the hours each one takes. Building stays cheaper when the suite is small, when a hard constraint rules out a hosted platform, or when running test infrastructure is already something your team does well. Still have additional questions? ## Keep reading. [Resources Best Puppeteer Alternatives for Browser Automation Compare the best Puppeteer alternatives for browser automation, E2E testing, and web scraping. Explore Playwright, Selenium, Cypress, Momentic, and more. Wei-Wei Wu 8 min read](/blog/puppeteer-alternatives)[Resources Best Qodex Alternatives for UI Testing Compare the best Qodex alternatives for UI testing, including Momentic, QA Wolf, mabl, Testim, and more. Explore AI-powered testing, self-healing locators, and web and mobile support. Wei-Wei Wu 8 min read](/blog/qodex-alternatives)[Resources Best Shiplight Alternatives for AI-Native Testing Compare the best Shiplight alternatives for AI-native testing, including Momentic, Playwright, mabl, TestRigor, and QA Wolf. Explore self-healing, autonomous testing, mobile support, and more. Wei-Wei Wu 7 min read](/blog/shiplight-alternatives) ## Close the feedback loop. Point Momentic at your app. Free to start, no credit card. [Try for free](https://app.momentic.ai/signup) [Contact sales](/sales)