Firefox Home (New Tab)¶
All files related to Firefox Home, which includes content that appears on
about:welcome, can be found in the
Some of these source files (such as
.sass) require an additional build step.
We are working on migrating this to work with
mach, but in the meantime, please
follow the following steps if you need to make changes in this directory:
No build step is necessary. Use
mach and run mochitests according to your regular Firefox workflow.
You will need the following:
Node.js 10+ (On Mac, the best way to install Node.js is to use the install link on the Node.js homepage)
npm (packaged with Node.js)
To install dependencies, run the following from the root of the mozilla-central repository.
mach to call
node commands will ensure you’re using the correct versions of Node and npm.)
(cd browser/components/newtab && ../../../mach npm install)
Which files should you edit?¶
You should not make changes to
.css files in
browser/components/newtab/data directory. Instead, you should edit the
Building assets and running Firefox¶
To build assets and run Firefox, run the following from the root of the mozilla-central repository:
./mach npm run bundle --prefix=browser/components/newtab && ./mach build && ./mach run
Continuous development / debugging¶
./mach npm run watchmc --prefix=browser/components/newtab will start a process that watches files in
activity-stream and rebuilds the bundled files when JS or CSS files change.
IMPORTANT NOTE: This task will add inline source maps to help with debugging, which changes the memory footprint.
Do not use the
watchmc task for profiling or performance testing!
The majority of New Tab / Messaging unit tests are written using
mocha, and other errors that may show up there are
SCSS issues flagged by
sasslint. These things
are all run using
npm test under the
newtab slug in Treeherder/Try, so if
that slug turns red, these tests are what is failing. To execute them, do this:
./mach npm test --prefix=browser/components/newtab
These tests are not currently run by
mach test, but there’s a
task filed to fix that.
Windows isn’t currently supported by
To run newtab specific tests that aren’t covered by
mach lint and
./mach npm run lint:sasslint --prefix=browser/components/newtab ./mach npm run testmc:build --prefix=browser/components/newtab ./mach npm run testmc:unit --prefix=browser/components/newtab
Mochitests and xpcshell tests run normally, using
Our testing setup will run code coverage tools in addition to just the unit tests. It will error out if the code coverage metrics don’t meet certain thresholds.
If you see any missing test coverage, you can inspect the coverage report by running
./mach npm test --prefix=browser/components/newtab && ./mach npm run debugcoverage --prefix=browser/components/newtab