Developer’s guide


This guide assumes you have cloned and built the geojs repository according to the Quick start guide.

The selenium testing infrastructure of Geojs is run via CTest, it assumes that the testing “server” is started prior to execution. To start the server, just run

npm run start-test

This will start a server on the default port of 30100. The port and selenium host names are configurable with cmake. For example inside the Kitware firewall, you can run the following to test on the selenium node on garant

cmake -DSELENIUM_TESTS=ON -DSELENIUM_HOST=garant /path/to/geojs
ctest -VV

You may need to also set the variable TESTING_HOST to your computer’s IP address reachable by the selenium node.


Typically, CMake is used to build outside of the source tree. This means you would create a new directory somewhare and point cmake to the geojs source directory. You may need to rerun cmake and make after making changes to your code for everything to build correctly. Try running ccmake /path/to/geojs for a full list of configuration options.

Geojs employs several different frameworks for unit testing. These frameworks have been designed to make it easy for developers to add more tests as new features are added to the api.

Code quality tests

All javascript source files included in the library for deployment are checked against ESLint for uniform styling and strict for common errors patterns. The style rules for geojs are located in the .eslintrc file in the root of the repository. These tests are preformed automatically for every file added to the build; no additional configuration is required. You can run a quick check of the code style outside of CMake by running npm run lint.

Headless browser testing

Geojs uses PhantomJS for headless browser testing of core utilities. Unfortunately because PhantomJS does not support webgl at this time, so code paths requiring gl must be either mocked or run via selenium.

The headless unit tests should be placed in the tests/cases/ directory. All javascript files in this directory will be detected by the Karma test runner and executed automatically when you run npm run test. It is possible to debug these tests in a normal browser as well. Just run npm run start and browse to http://localhost:9876/debug.html. The test runner will automatically rebuild the tests as you modify files so there is no need to rerun this command unless you add a new file.

There are a number of utilities present in the file tests/test-utils.js that developers can use to make better unit tests. For example, a mocked vgl renderer can be used to hit code paths within gl rendered layers. There are also methods for mocking global methods like requestAnimationFrame to test complex, asynchronous code paths in a stable and repeatable manner. The Sinon testing library is also available to generate stubs, spies, and mocked methods. Because all tests share a global scope, they should be careful to clean up all mocking and instrumentation after running. Ideally, each test should be runnable independently and use jasmines beforeEach and afterEach methods for setup and tear down.

Selenium testing

Most tests for geojs require a full browser with webgl support. For these test, a framework based on Selenium is provided. This test framework is intentionally lightweight to allow for many different kinds of testing from simple Jasmine style unit tests to complicated mouse interactions with screenshot comparisons.

All selenium based tests should be placed inside subdirectories of testing/test-cases/selenium-tests. All subdirectories are assumed to be selenium tests by CMake and will be instrumented and run accordingly. Each subdirectory should, at a minimum, contain the following three files, which may be empty:

  1. include.css: CSS that will be concatenated into a style node in the head.
  2. include.html: HTML that will be concatenated into the body.
  3. include.js: Javascript source that will be concatenated into a script node in the head after the inclusion of the geojs source and all dependent libraries.

Generally, developers are free to put arbitrary content into these files; however, one convention must be followed for the default instrumentation to work correctly. The javascript source should be wrapped in a global function called startTest. This function will be called automatically by the testing framework after all of the instrumentation is in place and the page is loaded. The startTest function will be called with function as an argument that should be called when page is ready to run the unit tests. This is provided as a convenience for the default behavior of selenium_test.BaseTest.wait() with no arguments. Developers can extend this behavior as necessary to provide more complicated use cases. As an example, see the d3Animation test case which sets a custom variable in a callback script for a test that is run asynchronously.

The compiled version of these tests are placed inside the deployment root so the users can manually see the test results. The path to each test is derived from the relative path inside testing/test-cases/selenium-tests/. For example, the test page in testing/test-cases/selenium-tests/osmLayer/ is available at http://localhost:30100/test/selenium/osmLayer/ after starting the test web server.

The unit tests themselves are derived from Python’s unittest module via a customized subclass selenium_test.BaseTest. Detailed documentation of the methods this class provides is given in the next section. Developers should feel free to extend this class with any generally useful methods as they become necessary for a wider variety test cases.

Example unit test

The following is a minimal example of a selenium unit test using the testing framework. More complicated examples can be found by examining the existing tests present in the source.


<div id="div-node"></div>


#div-node {
    text-align: center;


window.startTest = function (done) {
    $("#div-node").text("Hello, World!");


# Importing setupModule and tearDownModule will start up and
# shut down the web server automatically.
from selenium_test import FirefoxTest, setupModule, tearDownModule

# This test will run on firefox only.
class HelloWorld(FirefoxTest):
    testCase = ('hello', 'world')

    def test_main(self):
        # Resize the window to have consistent results.
        self.resizeWindow(640, 480)

        # Load the main html for this test directory.

        # Wait for it to be loaded.

        # Now we are ready to test the page.
        # The base class provide easy methods to test a screen shot.
        # This will take a screen shot and compare it against any
        # screenshots in the test image store at revision number 1.
        # Any failure here will raise an exception that will mark the
        # test as failed.
        self.screenshotTest('helloWorldScreenshot', revision=1)

Uploading screenshots to the image store

A script is provided in the source to help developers upload images to the data store in a way that they can be loaded automatically by the testing infrastructure. The script is built into test/ when selenium testing is enabled in CMake. When creating a new test (or updating a revision), the following is the recommended method for uploading test data for the example test hello/ described above.

# inside the build directory
python test/ ../testing/test-cases/selenium-tests/hello

The script will run all the tests in this directory and prompt you if you want to upload a new image in the event that a screenshot test has failed. If you intend to start a new revision, then the revision number should be changed in the unit test source before running this script. Note: you must have write permission in the MIDAS GeoJS community before you can upload new images. Contact a community administrator for an invitation.

Code coverage

Code coverage information is generated automatically for all headless unit tests by Karma’s test runner when running npm run test. The coverage information is submitted to codecov and cdash after every successful Travis run.