Tests and Benchmark
Tests
There exist several test suites for testing the correctness of a Markdown implementation. The original Markdown Test Suite is the standard which one needs to test against. The PHP Markdown suite contains the original test suite and several more tests (some specifically geared towards the extension of the PHP Markdown Extra package). I have used the latter test tool to roughly verify that kramdown is able to parse standard Markdown. However, since the syntax used by kramdown varies slightly from standard Markdown most of the tests fail - which is fine. When looking at the differences one can see that the failures result from these differences.
Besides using the above mentioned test suite kramdown comes with its own set of tests which is used to verify that the implementation matches the kramdown specification.
If you believe you have found a bug in the implementation, please follow these steps:
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Check the syntax page and see if the behaviour is not intended.
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If the behaviour is not intended and it seems that kramdown should parse some text in another fashion, please open a bug report and attach two files: one with the text and one with the HTML conversion you think is correct.
Benchmark
kramdown comes with a small benchmark to test how fast it is in regard to four other Ruby Markdown implementations: Maruku, BlueFeather, BlueCloth, RDiscount and Redcarpet. The first two are written using only Ruby, the latter three are written in C and need to be compiled.
As one can see below, kramdown is currently (January 2019) ~3x faster than Maruku, ~6.2x faster than BlueFeather but ~24x slower than RDiscount and ~86x slower than Redcarpet:
Running tests on 2019-01-20 under ruby 2.6.0p0 (2018-12-25 revision 66547) [x86_64-linux]
Test using file mdsyntax.text and 20 runs
Rehearsal --------------------------------------------------------
kramdown 2.0.0 0.374321 0.000000 0.374321 ( 0.381475)
Maruku 0.7.3 0.989168 0.007352 0.996520 ( 0.996109)
BlueFeather 0.41 1.938166 0.007986 1.946152 ( 1.943958)
BlueCloth 2.2.0 0.021138 0.000013 0.021151 ( 0.021130)
RDiscount 2.2.0.1 0.010207 0.000025 0.010232 ( 0.010221)
redcarpet 3.4.0 0.003311 0.000000 0.003311 ( 0.003313)
----------------------------------------------- total: 3.351687sec
user system total real
kramdown 2.0.0 0.309409 0.000000 0.309409 ( 0.309063)
Maruku 0.7.3 0.876370 0.023992 0.900362 ( 0.900120)
BlueFeather 0.41 1.933912 0.000000 1.933912 ( 1.931839)
BlueCloth 2.2.0 0.020436 0.000004 0.020440 ( 0.020420)
RDiscount 2.2.0.1 0.012775 0.000007 0.012782 ( 0.012771)
redcarpet 3.4.0 0.003564 0.000000 0.003564 ( 0.003558)
Real time of X divided by real time of kramdown
Maruku 2.9124
BlueFeather 6.2506
BlueCloth 0.0661
RDiscount 0.0413
redcarpet 0.0115
Test using file mdbasics.text and 20 runs
Rehearsal --------------------------------------------------------
kramdown 2.0.0 0.066966 0.000000 0.066966 ( 0.066896)
Maruku 0.7.3 0.185764 0.000000 0.185764 ( 0.185566)
BlueFeather 0.41 0.406975 0.000000 0.406975 ( 0.406544)
BlueCloth 2.2.0 0.006025 0.000000 0.006025 ( 0.006018)
RDiscount 2.2.0.1 0.002848 0.000000 0.002848 ( 0.002845)
redcarpet 3.4.0 0.000930 0.000000 0.000930 ( 0.000929)
----------------------------------------------- total: 0.669508sec
user system total real
kramdown 2.0.0 0.064527 0.000000 0.064527 ( 0.064457)
Maruku 0.7.3 0.182119 0.000000 0.182119 ( 0.181926)
BlueFeather 0.41 0.403922 0.000000 0.403922 ( 0.403494)
BlueCloth 2.2.0 0.006585 0.000000 0.006585 ( 0.006576)
RDiscount 2.2.0.1 0.003949 0.000000 0.003949 ( 0.003944)
redcarpet 3.4.0 0.001066 0.000000 0.001066 ( 0.001063)
Real time of X divided by real time of kramdown
Maruku 2.8224
BlueFeather 6.2599
BlueCloth 0.102
RDiscount 0.0612
redcarpet 0.0165
And here are some graphs which show the execution times of the various kramdown releases on different Ruby interpreters:
