--- title: Always Check Your Tests Against Faulty Inputs «... description: A developer shares a hard-learned testing lesson: after publishing an integration test designed to catch incorrect OSPF network types in netlab-generated... canonical: https://daily.dev/posts/always-check-your-tests-against-faulty-inputs-ipspace-net-blog-ksolouzw1 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Always Check Your Tests Against Faulty Inputs « ipSpace.net blog | daily.dev og:description: A developer shares a hard-learned testing lesson: after publishing an integration test designed to catch incorrect OSPF network types in netlab-generated... og:url: https://daily.dev/posts/always-check-your-tests-against-faulty-inputs-ipspace-net-blog-ksolouzw1 og:image: https://api.daily.dev/og/posts/KsOLOUZw1.png og:image:alt: Always Check Your Tests Against Faulty Inputs « ipSpace.net blog og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Always Check Your Tests Against Faulty Inputs « ipSpace.net blog **[ipSpace.net Blog](https://daily.dev/sources/ipspace)** · 1 min read · 0 upvotes · 0 comments ## Summary A developer shares a hard-learned testing lesson: after publishing an integration test designed to catch incorrect OSPF network types in netlab-generated configurations, a reader pointed out the test would never actually detect the error — OSPF adjacency establishes even with mismatched network types. The core mistake was verifying the test passes under correct conditions without verifying it fails under incorrect ones. The key takeaway: always validate your tests against faulty inputs, and be especially wary of false positives, which silently mask real failures until something breaks badly. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What is the difference between a false positive and false negative in software testing and which is worse? A false positive in testing means the test claims things work when they are actually broken; a false negative means the test claims things are broken when they are actually fine. False positives are more dangerous because you won't know you have a problem until something fails badly enough to be noticed, whereas false negatives surface immediately and can be fixed quickly. _Engineers chasing silent test failures find the patterns behind them on daily.dev._ ## Similar posts on daily.dev - [The OSPF MTU Mismatch Saga « ipSpace.net blog](https://daily.dev/posts/the-ospf-mtu-mismatch-saga-ipspace-net-blog-jmtvuzjm6) · ipSpace.net Blog · 0 upvotes · 0 comments - [Google Testing Blog: Choosing Values for Robust Tests](https://daily.dev/posts/google-testing-blog-choosing-values-for-robust-tests-z8ev5bpcf) · Google Testing · 0 upvotes · 0 comments - [Why Your Sandbox Never Quite Matches Production \(And Why That's Fine\)](https://daily.dev/posts/why-your-sandbox-never-quite-matches-production-and-why-that-s-fine--wbqlsnj0p) · Stack Overflow Blog · 0 upvotes · 0 comments - [The Regression Testing Habit That Changed How I Think About Shipping Code](https://daily.dev/posts/the-regression-testing-habit-that-changed-how-i-think-about-shipping-code-2dtsz5lot) · Code Like A Girl · 1 upvotes · 0 comments --- Tags: [#testing](https://daily.dev/tags/testing) [View this post on daily.dev](https://daily.dev/posts/always-check-your-tests-against-faulty-inputs-ipspace-net-blog-ksolouzw1) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Always Check Your Tests Against Faulty Inputs « ipSpace.net blog","url":"https://daily.dev/posts/always-check-your-tests-against-faulty-inputs-ipspace-net-blog-ksolouzw1","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/always-check-your-tests-against-faulty-inputs-ipspace-net-blog-ksolouzw1"},"datePublished":"2026-08-11T08:52:42.128Z","dateModified":"2026-08-11T08:57:58.850Z","description":"A developer shares a hard-learned testing lesson: after publishing an integration test designed to catch incorrect OSPF network types in netlab-generated...","image":"https://media.daily.dev/image/upload/s--1KxV4ohY--/f_auto/v1722860400/public/Placeholder%2007","thumbnailUrl":"https://media.daily.dev/image/upload/s--1KxV4ohY--/f_auto/v1722860400/public/Placeholder%2007","isAccessibleForFree":true,"articleSection":"ipSpace.net Blog","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"ipSpace.net Blog","logo":"https://media.daily.dev/image/upload/s--xS7E82MT--/f_auto,q_auto/v1786438303/logos/ipspace?_a=BAMAMicg0","url":"https://daily.dev/sources/ipspace"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/always-check-your-tests-against-faulty-inputs-ipspace-net-blog-ksolouzw1","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"testing","timeRequired":"PT1M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"ipSpace.net Blog","item":"https://daily.dev/sources/ipspace"},{"@type":"ListItem","position":3,"name":"Always Check Your Tests Against Faulty Inputs « ipSpace.net blog"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/always-check-your-tests-against-faulty-inputs-ipspace-net-blog-ksolouzw1#faq","mainEntity":[{"@type":"Question","name":"What is the difference between a false positive and false negative in software testing and which is worse?","acceptedAnswer":{"@type":"Answer","text":"A false positive in testing means the test claims things work when they are actually broken; a false negative means the test claims things are broken when they are actually fine. 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