iwmlib/doctest.html

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2019-03-21 09:57:27 +01:00
<!doctype html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Doctests</title>
<link rel="stylesheet" href="../lib/3rdparty/highlight/styles/default.css">
<link rel="stylesheet" href="../css/doctest.css">
<script src="../lib/3rdparty/highlight/highlight.pack.js"></script>
<script src="../lib/3rdparty/all.js"></script>
<script src="all.js"></script>
</head>
<body onload="Doctest.run()">
<main>
<h1>
Doctests
</h1>
<p>
Doctests are explanatory descriptions of programs with executable code examples.
Their main purpose is to explicate requirements, assumptions,
and relationships between components that are difficult to understand from
traditional API documentation. At the same time they provide tests of core
functionality.
</p>
<p>Doctests are written as HTML5+JavaScript pages with embedded script tags
marked by a <code>"doctest"</code> css class:
<pre><code>&lt;script class="doctest"&gt;</code></pre>
These scripts are evaluated and thereby tested when the page loads. See the
source of this page for examples.
Typically doctests are started by a
<pre><code>&lt;body onload="Doctest.run()"&gt;</code></pre>
call. This method loops over all script elements with a <code>"doctest"</code>
css class and replaces these scripts with <code>&lt;pre&gt;</code> tags that
(unlike<code>&lt;script&gt;</code> tags) are visible to the user.
</p>
<p>Let's look at an example of a simple program that uses a composite design
pattern. A node with a query component that can be reused in other classes:</p>
<script class="doctest">
class Query {
constructor(node) {
this.node = node
}
search(text) {
// Typically this would be part of an async callback mechanim.
// Here we simulate this async call. The main assumption is that the
// Node class has a related callback method.
this.node.queryResult("Result for: " + text)
}
}
class Node {
constructor(name) {
this.name = name
this.query = new Query(this)
}
queryResult(result) {
this.result = result
}
}
</script>
<p>We can now check whether the basic setup of our composite pattern works:</p>
<script class="doctest">
let node = new Node("Test")
node.query.search("What about...")
Doctest.expect(node.result, "Result for: What about...")
Doctest.expect(null, null)
</script>
<p>Looking at the source of this doctest you will see that the test is done
by the static <pre><code>Doctest.expect(expr, result)</code></pre> method. This
method throws an error which can be used standard browser development tools to
locate and trace the cause of the error.</p>
<h2>
References
</h2>
<ul>
<li><a href="http://highlightjs.readthedocs.io">Code Highlighting with highlight.js</a></li>
<li><a href="https://github.com/davidchambers/doctest">David Chamber's JavaScript Doctest</a></li>
</ul>
</main>
</body>