angular-cn/docs/DEBUG.md

Debugging Angular

The Angular project has comprehensive unit tests for the core packages and the tools. The core packages are tested both in the browser (via Karma) and on the server (via Node.js).

Debugging in Karma

Run the unit tests as normal using via the ./test.sh script. For example:

./test.sh browserNoRouter

Once the initial build has completed and the Karma server has started up, you can go to the Chrome browser that is automatically opened, usually pointing to http://localhost:9876. The script will sit watching for code changes, recompiling the changed files and triggering further runs of the unit tests in the browser.

In this browser there is a "DEBUG" link (in the top right corner). Clicking this link will open up a new tab that will run the unit tests and will not timeout, giving you time to step through the code.

Open up this tab's developer console to access the source code viewer where you can set breakpoints and interrogate the current stack and variables.

It is useful to focus your debugging on one test at a time by changing that test to be defined using the fit(...) function, rather than it(...). Moreover it can be helpful to place a debugger statement in this fit clause to cause the debugger to stop when it hits this test.

Debugging in Node

Run the unit tests as normal using the ./test.sh script, but add the --debug flag to the command. For example:

./test.sh node --debug

Once the initial building has completed, the script will watch for code changes, recompiling and running the unit tests via a tool call cjs-jasmine. Due to the --debug flag, each test run will create a debugging server listening on a port (such as 9229), which can be connected to by a debugger.

You can use Chrome as the debugger by navigating to chrome://inspect then clicking the "Open dedicated DevTools for Node" link. This will open up a Developer console, which will automatically connect to the debugging server.

It is useful to focus your debugging on one test at a time by changing that test to be defined using the fit(...) function, rather than it(...). Moreover it can be helpful to place a debugger statement in this fit clause to cause the debugger to stop when it hits this test.

Problem with node 6: at the time of writing, the node process does not tell the Chrome debugger when it has completed, and so the debugger is not able to automatically disconnect from listening to the debugging server. To solve this, just close the developer tools window after each run of the unit tests, before making changes to the code. This is fixed in node 8 and may be backported to node 6. This issue is tracked in https://github.com/nodejs/node/pull/12814#issuecomment-309908579.