Learning & reference

QA test-string library

Copy-paste strings that break input handling, each with a note on what it catches. Paste them into your fields, APIs and importers and confirm your app escapes, rejects or stores them safely. All strings are inert (they don't attack anything by being copied).

Use only on systems you are authorized to test.

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Guides and references for test data, file handling and AI evals. All free, no sign-up. See the full hub.

Synthetic data for AI evalsWhat you can download, what you buildRAG test corpusDocuments with extraction trapsJSONL for evalsThe format, and ten ways it breaksMock API for agentsRecords, pagination, failures on demandSafe test dataReserved domains, IPs, numbers & cardsSynthetic PIIFake people that reach nobodyTest card numbersEvery brand, declines, 3D SecureTest phone numbersReserved US, UK and Australian rangesReserved IP addressesDocumentation ranges and SSRF casesExample domains.test, .invalid, example.com, and trapsFilename compatibilityWhat breaks across Windows, Mac & LinuxFile systemsPOSIX, NTFS, APFS, ext4, SMB, NFS, NASFile signaturesMagic numbers that identify every formatCharacter encodingsUTF-8, UTF-16, BOM & normalizationUpload validationThe checklist, with a file for each checkMIME typesThe right Content-Type for every extensionHTTP status codesEvery code and when you actually see itDates & timesISO 8601, epoch, Excel serials, DSTHTTP headersContent-Type, Disposition, Range, CORSRegex cheat sheetSyntax, flags and ready-made patternsGenerate files (CLI)Make test files on any OSCrypto & certificatesSSL/PEM, hashing, encryptionWeb app testingWhat to test, with a file for each caseDesktop app testingPaths, names, encodings and savingMobile app testingPickers, photos, flaky networksCLI testingArguments, pipes and exit codesLarge file upload testingDefault limits, 413s and exact sizes1 GB test file1 GB and 2 GB, with SHA-25610 GB test fileMake one locally in secondsDownload speed test files10 MB to 2 GB of random data