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istanbul-middleware

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Connect middleware for getting code coverage numbers in functional tests for nodejs apps using istanbul.

Run the sample app at test/app to get a feel for how this works.

All of this is experimental and is known to work for narrow use-cases such as an express3 app. YMMV.

Server-side code coverage

This involves:

var im = require('istanbul-middleware'),
    isCoverageEnabled = (process.env.COVERAGE == "true"); // or a mechanism of your choice

//before your code is require()-ed, hook the loader for coverage
if (isCoverageEnabled) {
    console.log('Hook loader for coverage - ensure this is not production!');
    im.hookLoader(__dirname);
        // cover all files except under node_modules
        // see API for other options
}

// now require the rest of your code
var stuff = require('./lib'),
    express = require('express'),
    app = express();

// set up basic middleware
// ...

// add the coverage handler
if (isCoverageEnabled) {
    //enable coverage endpoints under /coverage
    app.use('/coverage', im.createHandler());
}

//add your router and other endpoints
//...

app.listen(80);

The above snippet adds the following endpoints to your app under /coverage

<table> <thead> <tr> <th>URL</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td><code>GET&nbsp;/</code></td> <td> Dynamic code coverage HTML report showing live coverage. Clickable with drill-downs just like the static version </td> </tr> <tr> <td><code>POST&nbsp;/reset</code></td> <td>Reset coverage to baseline numbers</td> </tr> <tr> <td><code>GET&nbsp;/download</code></td> <td>Download a zip file with coverage JSON, HTML and lcov reports</td> </tr> <tr> <td><code>POST&nbsp;/client</code></td> <td> Allows you to post a coverage object for client-side code coverage from the browser. Must be a JSON object with a <code>Content-type: application/json</code> header. This object is aggregated with the stats already present on the server </td> </tr> </tbody> </table>

Client-side coverage

This involves:

The API for this is highly experimental given the number of moving parts. But, it roughly looks like this:

var path = require('path'),
    im = require('istanbul-middleware');

// do the server side stuff as described above

// add a client handler at the appropriate place
// (before your static handler, for example)
// all JS files under here will be sent instrumented to the browser
// see API below for additional options (e.g. ignoring framework code)
app.use(im.createClientHandler(__dirname));

// however, it will only reliably work for simple cases
// such as absolute URLs to the JS.
// you still need to post the coverage numbers to the
//server from your browser tests

You can write your own custom middleware and completely ignore this library's client handler. As in:

app.use(function (req, res, next) {
    if (isJSRequiringCoverage(req)) {
        var file = getFilePath(req), //translate request to file name to be delivered
            code = readTheCodeFromFile(file), //use async for a real implementation
            instrumenter = im.getInstrumenter();
        res.send(instrumenter.instrumentSync(code, file));
            //exception handling omitted for brevity
    } else {
        next();
    }
});

API

istanbulMiddleware.hookLoader(rootOrMatcher, instrumenterOpts)

hooks require for coverage using istanbul.

rootOrMatcher can be:

instrumenterOpts is an optional object with additional options to be passed to the istanbul instrumenter. See the API docs in istanbul for more information. In addition, options can also contain the postLoadHook key that is passed to istanbul.hook.hookRequire()

istanbulMiddleware.createHandler(opts)

returns connect middleware that exposes additional endpoints for coverage. Endpoints exposed are documented in the summary.

opts is optional and currently only supports one flag.

istanbulMiddleware.createClientHandler(root, opts)

returns connect middleware similar to the static middleware to return instrumented JS to the client. The default behavior of the middleware is to intercept all GET requests to Javascript files and return the instrumented version by deriving the path of the file from the URL, instrumenting the code and sending the instrumented version in the response.

opts is an optional object with the following supported keys:

An example of a matcher function could be:

function ignoreFrameworks(req) {
    var parsed = require('url').parse(req.url);
    return parsed.pathname && parsed.pathname.match(/\.js$/) && !parsed.pathname.match(/jquery/);
}

For all other cases where the client handler provided by this library is not good enough, just write your own middleware as documented in the summary.

istanbulMiddleware.getInstrumenter()

returns the instrumenter object that is created as a side-effect of the hookLoader call. Useful for custom client-side instrumentation to ensure that the instrumentation is done with the same options for all code.

Third-party libraries

The following third-party libraries are used by this module: