zulip/docs/testing.md

Testing and writing tests
=========================

Running tests
-------------

To run everything, just use `./tools/test-all`. This runs lint checks,
web frontend / whole-system blackbox tests, and backend Django tests.

If you want to run individual parts, see the various commands inside
that script.

### Schema and initial data changes

If you change the database schema or change the initial test data, you
have to regenerate the pristine test database by running
`tools/do-destroy-rebuild-test-database`.

### Wiping the test databases

You should first try running: `tools/do-destroy-rebuild-test-database`

If that fails you should try to do:

    sudo -u postgres psql
    > DROP DATABASE zulip_test;
    > DROP DATABASE zulip_test_template;

and then run `tools/do-destroy-rebuild-test-database`

#### Recreating the postgres cluster

> **warning**
>
> **This is irreversible, so do it with care, and never do this anywhere
> in production.**

If your postgres cluster (collection of databases) gets totally trashed
permissions-wise, and you can't otherwise repair it, you can recreate
it. On Ubuntu:

    sudo pg_dropcluster --stop 9.1 main
    sudo pg_createcluster --locale=en_US.utf8 --start 9.1 main

### Backend Django tests

These live in `zerver/tests/tests.py` and `zerver/tests/test_*.py`. Run
them with `tools/test-backend`.

### Web frontend black-box casperjs tests

These live in `frontend_tests/casper_tests/`. This is a "black box"
test; we load the frontend in a real (headless) browser, from a real dev
server, and simulate UI interactions like sending messages, narrowing,
etc.

Since this is interacting with a real dev server, it can catch backend
bugs as well.

You can run this with `./tools/test-js-with-casper` or as
`./tools/test-js-with-casper 05-settings.js` to run a single test file
from `frontend_tests/casper_tests/`.

#### Debugging Casper.JS

Casper.js (via PhantomJS) has support for remote debugging. However, it
is not perfect. Here are some steps for using it and gotchas you might
want to know.

To turn on remote debugging, pass `--remote-debug` to the
`./frontend_tests/run-casper` script. This will run the tests with port
`7777` open for remote debugging. You can now connect to
`localhost:7777` in a Webkit browser. Somewhat recent versions of Chrome
or Safari might be required.

-   When connecting to the remote debugger, you will see a list of
    pages, probably 2. One page called `about:blank` is the headless
    page in which the CasperJS test itself is actually running in. This
    is where your test code is.
-   The other page, probably `localhost:9981`, is the Zulip page that
    the test is testing---that is, the page running our app that our
    test is exercising.

Since the tests are now running, you can open the `about:blank` page,
switch to the Scripts tab, and open the running `0x-foo.js` test. If you
set a breakpoint and it is hit, the inspector will pause and you can do
your normal JS debugging. You can also put breakpoints in the Zulip
webpage itself if you wish to inspect the state of the Zulip frontend.

You can also check the screenshots of failed tests at `/tmp/casper-failure*.png`.

If you need to use print debugging in casper, you can do using
`casper.log`; see <http://docs.casperjs.org/en/latest/logging.html> for
details.

An additional debugging technique is to enable verbose mode in the
Casper tests; you can do this by adding to the top of the relevant test
file the following:

>     var casper = require('casper').create({
>        verbose: true,
>        logLevel: "debug"
>     });

This can sometimes give insight into exactly what's happening.

### Web frontend unit tests

As an alternative to the black-box whole-app testing, you can unit test
individual JavaScript files that use the module pattern. For example, to
test the `foobar.js` file, you would first add the following to the
bottom of `foobar.js`:

>     if (typeof module !== 'undefined') {
>         module.exports = foobar;
>     }

This makes `foobar.js` follow the CommonJS module pattern, so it can be
required in Node.js, which runs our tests.

Now create `frontend_tests/node_tests/foobar.js`. At the top, require
the [Node.js assert module](http://nodejs.org/api/assert.html), and the
module you're testing, like so:

>     var assert = require('assert');
>     var foobar = require('js/foobar.js');

(If the module you're testing depends on other modules, or modifies
global state, you need to also read [the next
section](handling-dependencies_).)

Define and call some tests using the [assert
module](http://nodejs.org/api/assert.html). Note that for "equal"
asserts, the *actual* value comes first, the *expected* value second.

>     (function test_somefeature() {
>         assert.strictEqual(foobar.somefeature('baz'), 'quux');
>         assert.throws(foobar.somefeature('Invalid Input'));
>     }());

The test runner (index.js) automatically runs all .js files in the
frontend\_tests/node directory.

#### Coverage reports

You can automatically generate coverage reports for the JavaScript unit
tests. To do so, install istanbul:

>     sudo npm install -g istanbul

And run test-js-with-node with the 'cover' parameter:

>     tools/test-js-with-node cover

Then open `coverage/lcov-report/js/index.html` in your browser. Modules
we don't test *at all* aren't listed in the report, so this tends to
overstate how good our overall coverage is, but it's accurate for
individual files. You can also click a filename to see the specific
statements and branches not tested. 100% branch coverage isn't
necessarily possible, but getting to at least 80% branch coverage is a
good goal.

Writing tests
-------------

### Writing Casper tests

Probably the easiest way to learn how to write Casper tests is to study
some of the existing test files. There are a few tips that can be useful
for writing Casper tests in addition to the debugging notes below:

-   Run just the file containing your new tests as described above to
    have a fast debugging cycle.
-   With frontend tests in general, it's very important to write your
    code to wait for the right events. Before essentially every action
    you take on the page, you'll want to use `waitForSelector`,
    `waitUntilVisible`, or a similar function to make sure the page or
    elemant is ready before you interact with it. For instance, if you
    want to click a button that you can select via `#btn-submit`, and
    then check that it causes `success-elt` to appear, you'll want to
    write something like:

        casper.waitForSelector("#btn-submit", function () {
           casper.click('#btn-submit')
           casper.test.assertExists("#success-elt");
         });

    This will ensure that the element is present before the interaction
    is attempted. The various wait functions supported in Casper are
    documented in the Casper here:
    <http://docs.casperjs.org/en/latest/modules/casper.html#waitforselector>
    and the various assert statements available are documented here:
    <http://docs.casperjs.org/en/latest/modules/tester.html#the-tester-prototype>
-   Casper uses CSS3 selectors; you can often save time by testing and
    debugging your selectors on the relevant page of the Zulip
    development app in the Chrome javascript console by using e.g.
    `$$("#settings-dropdown")`.
-   The test suite uses a smaller set of default user accounts and other
    data initialized in the database than the development environment;
    to see what differs check out the section related to
    `options["test_suite"]` in
    `zilencer/management/commands/populate_db.py`.
-   Casper effectively runs your test file in two phases -- first it
    runs the code in the test file, which for most test files will just
    collect a series of steps (each being a `casper.then` or
    `casper.wait...` call). Then, usually at the end of the test file,
    you'll have a `casper.run` call which actually runs that series of
    steps. This means that if you write code in your test file outside a
    `casper.then` or `casper.wait...` method, it will actually run
    before all the Casper test steps that are declared in the file,
    which can lead to confusing failures where the new code you write in
    between two `casper.then` blocks actually runs before either of
    them. See this for more details about how Casper works:
    <http://docs.casperjs.org/en/latest/faq.html#how-does-then-and-the-step-stack-work>

### Handling dependencies in unit tests

The following scheme helps avoid tests leaking globals between each
other.

First, if you can avoid globals, do it, and the code that is directly
under test can simply be handled like this:

>     var search = require('js/search_suggestion.js');

For deeper dependencies, you want to categorize each module as follows:

-   Exercise the module's real code for deeper, more realistic testing?
-   Stub out the module's interface for more control, speed, and
    isolation?
-   Do some combination of the above?

For all the modules where you want to run actual code, add a statement
like the following to the top of your test file:

>     add_dependencies({
>         _: 'third/underscore/underscore.js',
>         util: 'js/util.js',
>         Dict: 'js/dict.js',
>         Handlebars: 'handlebars',
>         Filter: 'js/filter.js',
>         typeahead_helper: 'js/typeahead_helper.js',
>         stream_data: 'js/stream_data.js',
>         narrow: 'js/narrow.js'
>     });

For modules that you want to completely stub out, please use a pattern
like this:

>     set_global('page_params', {
>         email: 'bob@zulip.com'
>     });
>
>     // then maybe further down
>     global.page_params.email = 'alice@zulip.com';

Finally, there's the hybrid situation, where you want to borrow some of
a module's real functionality but stub out other pieces. Obviously, this
is a pretty strong smell that the other module might be lacking in
cohesion, but that code might be outside your jurisdiction. The pattern
here is this:

>     // Use real versions of parse/unparse
>     var narrow = require('js/narrow.js');
>     set_global('narrow', {
>         parse: narrow.parse,
>         unparse: narrow.unparse
>     });
>
>     // But later, I want to stub the stream without having to call super-expensive
>     // real code like narrow.activate().
>     global.narrow.stream = function () {
>         return 'office';
>     };

Manual testing (local app + web browser)
----------------------------------------

### Clearing the manual testing database

You can use:

    ./tools/do-destroy-rebuild-database

to drop the database on your development environment and repopulate
your it with the Shakespeare characters and some test messages between
them.  This is run automatically as part of the development
environment setup process, but is occasionally useful when you want to
return to a clean state for testing.

### JavaScript manual testing

debug.js has some tools for profiling Javascript code, including:

-   \`print\_elapsed\_time\`: Wrap a function with it to print the time
    that function takes to the javascript console.
-   \`IterationProfiler\`: Profile part of looping constructs (like a
    for loop or \$.each). You mark sections of the iteration body and
    the IterationProfiler will sum the costs of those sections over all
    iterations.

Chrome has a very good debugger and inspector in its developer tools.
Firebug for Firefox is also pretty good. They both have profilers, but
Chrome's is a sampling profiler while Firebug's is an instrumenting
profiler. Using them both can be helpful because they provide different
information.

Python 3 Compatibility
----------------------

Zulip is working on supporting Python 3, and all new code in Zulip
should be Python 2+3 compatible. We have converted most of the codebase
to be compatible with Python 3 using a suite of 2to3 conversion tools
and some manual work. In order to avoid regressions in that
compatibility as we continue to develop new features in zulip, we have a
special tool, tools/check-py3, which checks all code for Python 3
syntactic compatibility by running a subset of the automated migration
tools and checking if they trigger any changes. tools/check-py3 is run
automatically in Zulip's Travis CI tests to avoid any regressions, but
is not included in test-all since it is quite slow.

To run tooks/check-py3, you need to install the modernize and future
python packages (which are in the development environment's
requirements.txt file).

To run check-py3 on just the python files in a particular directory, you
can change the current working directory (e.g. cd zerver/) and run
check-py3 from there.