--- title: How to Get Error Locations with `?` in Rust Tests description: Svix engineers explain how to get precise error locations when using the `?` operator in Rust test functions, instead of the verbose `.unwrap()` calls or... canonical: https://daily.dev/posts/how-to-get-error-locations-with-in-rust-tests-1c6yigwlw twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: How to Get Error Locations with `?` in Rust Tests | daily.dev og:description: Svix engineers explain how to get precise error locations when using the `?` operator in Rust test functions, instead of the verbose `.unwrap()` calls or... og:url: https://daily.dev/posts/how-to-get-error-locations-with-in-rust-tests-1c6yigwlw og:image: https://api.daily.dev/og/posts/1C6yIgWLW.png og:image:alt: How to Get Error Locations with `?` in Rust Tests 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. # How to Get Error Locations with `?` in Rust Tests **[Svix Blog](https://daily.dev/sources/svix)** · 6 min read · 0 upvotes · 0 comments ## Summary Svix engineers explain how to get precise error locations when using the `?` operator in Rust test functions, instead of the verbose `.unwrap()` calls or backtrace-heavy anyhow errors. The technique relies on the `#[track_caller]` attribute combined with a custom `TestError` type whose `From` implementation panics with the caller location, giving concise, location-accurate failure messages without needing full debug info or deep backtraces. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How can I get the exact source location of a failing assertion when using the ? operator in a Rust test function? Define a custom error type, such as an empty TestError enum, and implement From for it using the #[track_caller] attribute, panicking inside the from function with the debug-printed value. Because #[track_caller] passes the call site through as a hidden parameter, the panic reports the location where ? was used, even though the panic technically occurs inside the From impl. _Developers wiring up cleaner Rust test failures can find more patterns like this through daily.dev._ ### Why doesn't anyhow give me a useful error location when a Rust test using ? fails? By default, anyhow's Err output only prints the error message, not a source location, unless full backtraces are captured, and those backtraces can be around 26 frames deep on Linux and require full debug info to include exact locations. Many projects strip debug info to save compile time and disk space, which removes the location data from the backtrace entirely. _Teams weighing anyhow against custom error handling in Rust tests can track such trade-offs on daily.dev._ ## Similar posts on daily.dev - [Stop Forwarding Errors, Start Designing Them](https://daily.dev/posts/stop-forwarding-errors-start-designing-them-llnspffx6) · Lobsters · 1 upvotes · 0 comments - [Scoped Error in Rust](https://daily.dev/posts/scoped-error-in-rust-wwq3iomnl) · Lobsters · 6 upvotes · 1 comments - [Nice CLI Crash Reports in Rust](https://daily.dev/posts/nice-cli-crash-reports-in-rust-refjbwkvz) · Pascal’s scribbles · 1 upvotes · 0 comments --- Tags: [#testing](https://daily.dev/tags/testing), [#rust](https://daily.dev/tags/rust) [View this post on daily.dev](https://daily.dev/posts/how-to-get-error-locations-with-in-rust-tests-1c6yigwlw) ```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":"How to Get Error Locations with `?` in Rust Tests","url":"https://daily.dev/posts/how-to-get-error-locations-with-in-rust-tests-1c6yigwlw","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/how-to-get-error-locations-with-in-rust-tests-1c6yigwlw"},"datePublished":"2026-08-23T07:21:00.174Z","dateModified":"2026-08-23T07:25:19.132Z","description":"Svix engineers explain how to get precise error locations when using the `?` operator in Rust test functions, instead of the verbose `.unwrap()` calls or...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/6f97f12e7710c84015317be042db94c9?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/6f97f12e7710c84015317be042db94c9?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Svix 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":"Svix Blog","logo":"https://media.daily.dev/image/upload/s--Shf9MlOr--/f_auto,q_auto/v1787469609/logos/svix?_a=BAMAMicg0","url":"https://daily.dev/sources/svix"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/how-to-get-error-locations-with-in-rust-tests-1c6yigwlw","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"testing,rust","timeRequired":"PT6M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Svix Blog","item":"https://daily.dev/sources/svix"},{"@type":"ListItem","position":3,"name":"How to Get Error Locations with `?` in Rust Tests"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/how-to-get-error-locations-with-in-rust-tests-1c6yigwlw#faq","mainEntity":[{"@type":"Question","name":"How can I get the exact source location of a failing assertion when using the ? operator in a Rust test function?","acceptedAnswer":{"@type":"Answer","text":"Define a custom error type, such as an empty TestError enum, and implement From for it using the #[track_caller] attribute, panicking inside the from function with the debug-printed value. Because #[track_caller] passes the call site through as a hidden parameter, the panic reports the location where ? was used, even though the panic technically occurs inside the From impl. Developers wiring up cleaner Rust test failures can find more patterns like this through daily.dev."}},{"@type":"Question","name":"Why doesn't anyhow give me a useful error location when a Rust test using ? fails?","acceptedAnswer":{"@type":"Answer","text":"By default, anyhow's Err output only prints the error message, not a source location, unless full backtraces are captured, and those backtraces can be around 26 frames deep on Linux and require full debug info to include exact locations. Many projects strip debug info to save compile time and disk space, which removes the location data from the backtrace entirely. Teams weighing anyhow against custom error handling in Rust tests can track such trade-offs on daily.dev."}}]} ```