WebKitSite/quality/reduction.html

<?php
    $title = "Test Case Reduction";
    include("../header.inc");
?>
    <h2>Test Case Reduction</h2>

    <h3>A general guide to test case reduction</h3>
    <p>
        The basic idea behind bug reduction is to take a page that demonstrates a problem and
        remove as much content as possible while still reproducing the original problem.
    </p>

    <h4>Why is this needed?</h4>
    <p>
        A reduced test case can help identify the central problem on the
        page by eliminating irrelevant information, i.e., portions of the HTML
        page&rsquo;s structure that have nothing to do with the problem.
        With a reduced test case, the development team will spend
        less time identifying the problem and more time determining the
        solution. Also, since a site can change its content or design, the
        problem may no longer occur on the real-world site. 
        By constructing a test case you can capture the initial problem.
    </p>

    <h4>The first steps</h4>
    <p>
        Really the first step in reducing a page is to identify that main
        problem of the page. For example:
        <ul>
            <li>Does the page have text overlapping an image? </li>
            <li>Is there a form button that fails to work?</li>
            <li>Is there a portion of the page missing or misaligned?</li>
        </ul>

    <p>
        After you have made this determination, you need to create a local copy
        of the page created from the page source window. After saving this
        source, it&rsquo;s a good idea to put a <code>&lt;BASE&gt;</code> element in the
        <code>HEAD</code> so that any images/external style sheet or scripts that use a
        relative path will get loaded. After the <code>BASE</code> element has been added,
        load the local copy into the browser and verify that problem is still
        occurring. In this case, let&rsquo;s assume the problem is still present.
    </p>

    <h4>Work from top to bottom</h4>
    <p>
        In general, it&rsquo;s best to start from the top of the <code>&lt;DOCTYPE&gt;</code> and
        work down through the <code>HEAD</code> to the <code>BODY</code> element. Take a look at the HTML
        file in a text editor and view what types of elements are present in the
        <code>&lt;head&gt;</code>. Typically, the <code>HEAD</code> will include the <code>&lt;title&gt;</code>
        element, which is required, and elements such as <code>&lt;link&gt;</code>,
        <code>&lt;style&gt;</code> and <code>&lt;script&gt;</code>.
    </p>
    <p>
        The reduction process is to remove one element at a time, save, and reload the
        test case. If you have removed the element and the page is still
        displaying the problem, continue with the next element. If removing an
        element in the <code>HEAD</code> causes the problem to not occur, you may have found
        one piece of the problem. Re-add this element back into the <code>HEAD</code>,
        reload the page and confirm the problem is still occurring and move
        on to the next element in the <code>HEAD</code>.
    </p>
    
    <h4>Finished the <code>HEAD</code>? Continue with the <code>BODY</code>!</h4>
    <p>
        Once the <code>HEAD</code> element has been reduced, you need to start reducing
        the number of required elements in the <code>BODY</code>. This will tend to be the
        most time consuming since hundreds (thousands) of elements will be
        present. The general practice is start removing elements by both their
        <code>&lt;start&gt;</code> and <code>&lt;/end&gt;</code> elements. This is especially true for
        tables, which are frequently nested. You can speed up this process by
        selecting groups of elements and removing them but ideally you need to
        save and reload the test case each time to verify the problem is
        happening.
    </p>
    
    <h4>Another method</h4>
    <p>
        Another way to help you identify unnecessary elements is to temporarily
        deselect the option &ldquo;Enable Javascript&rdquo; in Safari preferences. If you turn this option
        off and loading your test case still reproduces the problem, then any
        script elements that are present can be removed since they are not a
        factor in this issue. Let&rsquo;s say that you have reduced the page down to
        a nested table with an ordered list with an <code>&lt;link&gt;</code> element that need
        to be present. It&rsquo;s good practice to identify that CSS rule that is
        being in the external file and add it directly to the test case. Create
        a <code>&lt;style&gt;</code> <code>&lt;/style&gt;</code> in the head and copy/paste the contents
        of the .css file into this style element. Remove the <code>&lt;link&gt;</code> and
        save the changes. Load the test case and verify the problem is still
        occurring. Now manually delete or comment out each CSS rule until you
        have just the required set of rules to reproduce.
    </p>
    
    <h4>Adding to the bug</h4>
    <p>
        When you&rsquo;ve finished your reduction, you should add it to the bug. It&rsquo;s quite likely
        that in the process of reducing, you have found the root cause of the problem, so
        you are able to set the right component. Don&rsquo;t forget to add the <code>HasReduction</code> keyword to the bug
        (and remove the <code>NeedsReduction</code> keyword, if present). If you do not have the rights to change
        the component or the keywords, read about how to get them in this <a href="bugzilla.html">document
        about Bugzilla</a>.
    </p>

    <h4>Ready to begin?</h4>
    <p>
        In addition to providing reductions for bugs that you&rsquo;ve found, you can help
        by reducing any of the <a href="/needs-reduction">bugs in Bugzilla tagged
        with the <code>NeedsReduction</code> keyword</a>.
    </p>
<?php include("../footer.inc"); ?>