npm package

Providing predefined files of certain types to test functions working with them

Testing functions that work with files benefits from having testfiles at hand, as well for the file type(s) that must be handled as for those that must be excluded from handling to prevent errors.

The goal of this package is to test if a function can identify, distinguish and reject file types. Providing all possible properties of a certain type and narrowing down to specific configurations and possible errors goes far beyond its scope (this should be better done with packages of multiple testfiles for only one file type).

The package installs an extensible collection of small testfiles for different file types and a function to get a path for a testfile of a specific type to be used in a function call (see below). Note that full MIME types are used for easier distinguishing between e.g. image/jpeg and video/JPEG, moreover MIME types are clear concerning e.g. “jpeg” vs. “jpg” and wrongly set file extensions may crash your application, i.e. you should already prefer them in your code. Refer to sources like MDN’s list of common media types to clarify historical idiosyncrasies like .txt files being text/plain or .mp3 files being audio/mpeg.

The provided testfiles have real content and structure to distinguish e.g. actual plaintext files from CSS files - usually tools like mimetype and the well established Linux file command do not analyse contents and would classify an empty xy.css as text/css or a CSS file xy with missing .css extension as text/plain as a default for any file missing a “magic” file signature (not to speak of plain fakes like Bun’s “file.type” and Deno’s “contentType” that fully rely on a file’s extension). The provided testfiles have enough content to support possible file type checking by taking samples from their beginning.

Note that not all discussed types are provided yet, but you could add them yourself to the local directory (see Details).

hh lohmann <hh.lohmann@gmail.com>

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Synopsis

  import { predefinedTestfile } from 'predefined-test-files'

  myFunctionConsumingFiles( predefinedTestfile( mimeType ) )

  const arrayOfExistingTypessMatchingSearch = predefinedTestfile( `search:` + mimeType )

Parameters

mimeType

• without search: prefix: Exact MIME type identifier of requested testfile
  • e.g. image/jpeg will return the absolute path to testfile.image.jpeg
• with search: prefix: Part of MIME type identifier to search testfiles for
  • e.g. search:image/ may return [ 'image/jpeg', 'image/png' ]
  • meant to check if testfiles for defined MIME types are available, not for guessing probably defined types or their spelling

Returns

• without search: prefix = predefinedTestfile( mimeType )
  • Absolute path to testfile.[ mimeType.top ].[ mimeType.sub ]
  • [ mimeType.top ] / [ mimeType.sub ]: see Details
• with search: prefix = predefinedTestfile( search: + mimeType )
  • Array of MIME types for which testfiles exist
  • e.g. [ 'image/jpeg', 'image/png' ]

Examples

• Testing with PDF testfile

    myPdfReader( predefinedTestfile( 'application/pdf' ) )
  

• Testing with all existing “image/” testfiles

    predefinedTestfile( 'search:image/' )
    .forEach( value => {
      myImgProcessor( predefinedTestfile( value ) )
    } )
  

• Testing with all existing “/javascript” testfiles

    // This would help if an outdated documentation relies on
    // "application/javascript" which is officially replaced by
    // "text/javascript"
    predefinedTestfile( 'search:/javascript' )
    .forEach( value => {
      myJsValidator( predefinedTestfile( value ) )
    } )
  

• Handling not yet existing testfiles

    if( predefinedTestfile( 'search:image/bmp' ).length!==0 ){
      myImgProcessor( predefinedTestfile( 'image/bmp' ) )
    }
    else{
      console.log( 'Bitmaps currently not testable' )
    }
  

Caveats

• Intentionally no options for testing by properties like file size, naming etc. since these do not depend on the type of a file.

• Not intended for “meta types” (top level types) like “image”
  • You may utilize a forEach iteration to test exactly those image types that your function is expected to handle, e.g.

      ['gif','jpeg','png'].forEach( value => {
        yourFunction( predefinedTestfile( 'image/'+value ) )
      })
    

• Notorious ambiguities like CSV files with semicolons instead of commas / with or without a header line / double quotes or not etc. are regarded as a natural fate for your function working with “CSV” files, i.e. there are no different testfiles here, but only one adhering to the reference definiton give in the IANA registry

Installation

Pick for your preferred package manager:

  npm i predefined-test-files

  pnpm i predefined-test-files

  bun i predefined-test-files

  # For Yarn you should double check docs for your and / or
  # current Yarn version, newer versions do not treat `i package_name`
  # as an alias for `add ...` and exclude global installations
  yarn add predefined-test-files

Details

• This package uses the following terms:
  • “MIME type” as the well introduced traditional expression for that what is officially called “Media type”
  • MIME type identifier for the string uniquely identifying a MIME type, e.g. image/jpeg
  • mimeType.top for the part before the / in an identifier, e.g. image

    Note that the structure of a MIME type identifier is just implicitly defined over various RFCs, in practice it is a top level type like image with a subtype like jpeg connected by a slash /

  • mimeType.sub for the part after the / in an identifier, e.g. jpeg

• Possible MIME types are those listed in the official IANA registy

• The testfiles are stored for simplicity in ./node_modules/predefined-test-files/testfiles as testfile.[ mimeType.top ].[ mimeType.sub ]
  • This simple structure allows quick adding of testfiles in a local installation that are immediately found by predefinedTestfile
  • Manually added testfiles must have real content and structure
• predefinedTestfile returns an absolute path to testfile.[ mimeType.top ].[ mimeType.sub ]
  • e.g. /home/joe-doe/fantastic-project/node_moules/predefined-test-files/testfiles/testfile.application.pdf
  • Relative paths may not work in all contexts
  • Applications consuming relative paths in parameters are likely to resolve them internally to absolute paths anyway

Demo

See demos on GitHub Pages for this repo

Tests

• Code tests to be run with Node.js / Bun available in Source Code

Source Code

• GitHub: https://github.com/hh-lohmann/predefined-test-files

License

• MIT (see LICENSE.txt)

• Testfiles for top level types application, audio, font, image and video as well as for text/rtf are taken from Edmundas Ramanauskas’s file-type-mime package under MIT license (c) 2023 Edmundas Ramanauskas

References

Internet Assigned Numbers Authority (IANA): Media Types

• The authorative list of known Media Types (MIME types)
• https://www.iana.org/assignments/media-types/media-types.xhtml

Internet Assigned Numbers Authority (IANA): Top-Level Media Types

• https://www.iana.org/assignments/top-level-media-types/top-level-media-types.xhtml

mimetype / File-MimeInfo

• CLI to check files for MIME type
• https://codeberg.org/michielb/File-MimeInfo

MDN: Common media types (Web)

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/MIME_types/Common_types

Wikipedia: List of file signatures

• NB: File signatures are often called “magic number / pattern / bytes”
• https://en.wikipedia.org/wiki/List_of_file_signatures

Wikipedia: Request for Comments (RFC)

• https://en.wikipedia.org/wiki/Request_for_Comments

Linux “file” command

• Also known as the “Ian Darwin / Christos Zoulas implementation”
• https://man7.org/linux/man-pages/man1/file.1.html
• https://www.darwinsys.com/file/

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