Declarative unit testing, for everyone

HTML-first tests

While you can run any hTests in the browser, you can also write tests directly in HTML, without any JS file being involved.

These tests can only run in the browser, but can be useful for testing UI-heavy code. The pass-criteria extends beyond value matching or error catching, and could even be things like what CSS selectors match or what the DOM looks like. They are evaluated reactively, so if the HTML changes or the user interacts with the UI, relevant tests are re-evaluated. Last, they also support mocking basic interactions like click or focus, via HTML attributes.


Just include hTest on HTML pages with the appropriate format (see below).

<link rel="stylesheet" href="" crossorigin />
<script src="" crossorigin></script>

Creating new tests

The primary test format is reftests, i.e. automatic comparison of two things, typically app output with expected (reference) output. When the two match, the test passes (green), otherwise it fails (red).

You can create reftests by using a table with class="reftest". Each row is a new test. Typically these tables have two columns: output and expected. However, if your test requires initialization data, you can also have 3 columns, and the first one will be ignored in the matching.

Typically these tables are inside sections with HTML like the following:

	<table class="reftest">
		<!-- ...tests as <tr>s -->

This structure is not necessary for the reftests to work, but it allows you to isolate specific sections, which is often convenient when debugging. You can also isolate an individual row by Alt + double clicking.

Below is a short description of the syntax we support.

data-test attribute

This applies to either the whole table or individual tests and controls how the matching is done. By default the contents of the cells are compared which corresponds to data-test="contents".

Other useful values are:

Besides the built-in comparison functions, you can provide your own, by defining a JavaScript function, either as the content of the data-test attribute, or by defining a global function. It accepts the 2-3 cells of your test as arguments and should return a truthy value for pass and a falsy value for fail.

data-columns attribute

2 by default, which means there are two columns: ref and test. Set it to 3 or more for custom tests that need the previous columns for data.

data-click attribute

Automatic clicking on elements. It can be placed on either the whole table or individual tests. Its location specifies the root for the selector, if one is specified. Its syntax is (angle brackets indicate a parameter, square brackets mean that something is optional):

[<selector>] [wait <delay>s] [after <event name>] [<times> times]

The parameters can be specified in any order.


data-error attribute

Use on tests that should produce an error to pass. Use the data-error attribute on the <tr>, not the table cell. Put the expected error type in the "expected" table cell.

$out() and $outln() functions

Sometimes what is tested is pure JS output with no UI. While the JS-first mode is typically better for those use cases, it is possible to use HTML-first mode as well. In that case, use <script> tags and the $out() or $outln() functions. Their only difference is that $outln() also prints a line break.

Running tests

HTML-first tests can currently only run in the browser, by opening the HTML file.