tasty-golden

Golden tests support for tasty

https://github.com/UnkindPartition/tasty-golden

LTS Haskell 24.29:2.3.5
Stackage Nightly 2026-02-05:2.3.6
Latest on Hackage:2.3.6

See all snapshots tasty-golden appears in

MIT licensed by Roman Cheplyaka
Maintained by Roman Cheplyaka
This version can be pinned in stack with:tasty-golden-2.3.6@sha256:bca7b66bdc0238d63e82164993f684fd7751c95b67a2533088f658840e3400fa,2962

Module documentation for 2.3.6

Used by 2 packages in nightly-2026-02-05(full list with versions):
crackNum, tasty-golden

This package provides support for «golden testing».

A golden test is an IO action that writes its result to a file. To pass the test, this output file should be identical to the corresponding «golden» file, which contains the correct result for the test.

To get started with golden testing and this library, see Introduction to golden testing.

Command-line options

To see the command-line options, run your test suite with --help. Here’s an example output:

Mmm... tasty test suite

Usage: test [-p|--pattern PATTERN] [-t|--timeout DURATION] [-l|--list-tests]
            [-j|--num-threads NUMBER] [-q|--quiet] [--hide-successes]
            [--color never|always|auto] [--ansi-tricks ARG] [--accept]
            [--no-create] [--size-cutoff n]
            [--delete-output never|onpass|always]

Available options:
  -h,--help                Show this help text
  -p,--pattern PATTERN     Select only tests which satisfy a pattern or awk
                           expression
  -t,--timeout DURATION    Timeout for individual tests (suffixes: ms,s,m,h;
                           default: s)
  -l,--list-tests          Do not run the tests; just print their names
  -j,--num-threads NUMBER  Number of threads to use for tests
                           execution (default: # of cores/capabilities)
  -q,--quiet               Do not produce any output; indicate success only by
                           the exit code
  --hide-successes         Do not print tests that passed successfully
  --color never|always|auto
                           When to use colored output (default: auto)
  --ansi-tricks ARG        Enable various ANSI terminal tricks. Can be set to
                           'true' or 'false'. (default: true)
  --accept                 Accept current results of golden tests
  --no-create              Error when golden file does not exist
  --size-cutoff n          hide golden test output if it's larger than n
                           bytes (default: 1000)
  --delete-output never|onpass|always
                           If there is a golden file, when to delete output
                           files (default: never)

See also tasty’s README.

Maintainers

Roman Cheplyaka is the primary maintainer.

Oliver Charles is the backup maintainer. Please get in touch with him if the primary maintainer cannot be reached.

Changes

Changes

Version 2.3.6

  • Option --no-create-file now available internally as NoCreateFile (Issue #50)
  • Drop support for GHC 7, remove obsolete deriving Typeable
  • Tested with GHC 8.0 - 9.14.1

Andreas Abel, 2026-02-01

Version 2.3.5

  • Fixes for launching external processes (like diff) on Windows
  • Update the golden file on --accept if decoding the golden file failed with an exception
  • Do not depend on unix-compat

Version 2.3.4

  • Add an option to remove the output file after a test has run, if there is a golden file, or one has been created

Version 2.3.3.3

  • Fix a bug where goldenVsFileDiff would not create a missing golden file

Version 2.3.3.2

  • Fix a bug where the TASTY_SIZE_CUTOFF env. variable would be ignored

Version 2.3.3.1

  • Fix a bug with UTF-8 output

Version 2.3.3

  • Expose createDirectoriesAndWriteFile
  • Add --size-cutoff to truncate large golden test output
  • Restore support for GHC >= 7.8

Version 2.3.2.1

Create missing directories when writing golden files

Version 2.3.2

Add a --no-create flag

Version 2.3.1.3

Make the environment variable TASTY_ACCEPT=True work, and make the value case-insensitive (so TASTY_ACCEPT=true works, too)

Version 2.3.1.2

Docs: link to an introductory blog post

Version 2.3.1.1

Fix compatibility with optparse-applicative-0.13

Version 2.3.1

Intercept exceptions thrown by the test, adhering to the new tasty API contract.

Version 2.3.0.2

Switch from temporary-rc to temporary

Version 2.3.0.1

Impose a lower bound version constraint on bytestring.

Version 2.3

  • Accepting tests is no longer done by a separate ingredient; instead it is now an option that affects tests themselves.

    • --accept used to run only golden tests; now all tests are run, but only golden tests are affected by this option
    • when accepting, all the usual options apply (such as -j)
    • when accepting, the interace is the same as when running
    • defaultMain and acceptingTests are kept for compatibility, but do not do anything and are obsolete

  • When a golden test file does not exist, it is created automatically, even when --accept is not specified. You’ll see a message like

      UnboxedTuples:                 OK (0.04s)
    Golden file did not exist; created

  • No longer use lazy IO

    • ValueGetter type is gone (replaced by IO)
    • Because of that, the type of the primitive goldenTest is changed
    • vgReadFile function is gone (replaced by Data.ByteString.readFile)

Version 2.2.2.4

  • Warn when some tests threw exceptions during --accept
  • Properly handle exceptions; don’t swallow Ctrl-C

Version 2.2.2.3

Restore compatibility with older compilers

Version 2.2.2.1

Relax Cabal dependency

Version 2.2.2

Add findByExtension

Version 2.2.1.2

Catch exceptions when accepting golden tests

Version 2.2.1.1

Switch to temporary-rc

Version 2.2.1

  • Fix a bug where the result of the comparison function would reference yet unread data from a semiclosed file and the file gets closed, leading to a runtime exception
  • Export writeBinaryFile
  • Improve the docs
  • Update to work with tasty-0.8

Version 2.2.0.2

Update to work with tasty-0.7

Version 2.2.0.1

Update to work with tasty-0.5

Version 2.2

Migrate to ingredients

Version 2.1

Add goldenVsStringDiff

Version 2.0.1

Update to work with tasty-0.2

Version 2.0

Initial release of tasty-golden (derived from test-framework-golden-1.1.x)