'What's the right way to enable the node debugger with mocha's --debug-brk switch?
I have some debugger statements in my module under test and want to run mocha with --debug-brk set and hit my breakpoint so that I can inspect the state of my module. Unfortunately, whenever I run mocha with this option, I end up with a blank cursor on the next line. I can enter text, but there's nothing that appears to be processing my commands (it certainly doesn't look like the node debugger):
$ mocha --debug-brk tests.js -R spec
debugger listening on port 5858
[BLANK CURSOR]
Am I doing something wrong with how I'm launching mocha?
Solution 1:[1]
To answer the original question, even though I also suggest you look into node-inspector: you can use the CLI debugger built into node through mocha with the debug option, instead of the --debug or --debug-brk flags. (Notice the lack of dashes.)
In your example, instead, it would be:
$ mocha debug tests.js -R spec
debugger listening on port 5858
connecting... ok
break in node_modules/mocha/bin/_mocha:7
5 */
6
7 var program = require('commander')
8 , sprintf = require('util').format
9 , path = require('path')
debug> [CURSOR]
Again, debug as above in bold, with no dashes. (=
Solution 2:[2]
UPDATE
As of mocha 7.0.0, --debug-brk has been removed in favor of --inspect-brk
Using a recent version of nodejs (>=v6.3.0) and mocha (>=3.1.0), you can use V8 inspector integration.
V8 Inspector integration allows attaching Chrome DevTools to Node.js instances for debugging and profiling
Usage
--inspect activates V8 inspector integration, and --debug-brk adds a breakpoint at the beginning. Since nodejs v7.6.0 and mocha v3.3.0, you can use the --inspect-brk shorthand for --inspect --debug-brk
$ mocha --debug-brk --inspect
Debugger listening on port 9229.
Warning: This is an experimental feature and could change at any time.
To start debugging, open the following URL in Chrome:
chrome-devtools://devtools/remote/serve_file/@62cd277117e6f8ec53e31b1be58290a6f7ab42ef/inspector.html?experiments=true&v8only=true&ws=localhost:9229/node
With npm scripts
If you have a npm test script that uses mocha, you can pass the options from npm to your mocha script by using the end of option delimiter --:
$ npm test -- --inspect --debug-brk
Chrome tip
Instead of copy-pasting the url each time, go to chrome://inspect and click the appropriate link in the "Remote target" section.
Solution 3:[3]
I was able to get this to work using node-inspector. I run my test like you show in one shell:
mocha --debug-brk mocha/test.js
and then run node-inspector in a second shell:
node-inspector
Bringing up the URL that node-inspector spits out in a browser allows me to debug with the web inspector.
http://127.0.0.1:8080/debug?port=5858
Solution 4:[4]
If you have node-insector installed you can debug you Mocha tests without actually running node-inspector first. The easiest way is to
node-debug _mocha
That should start debugging the node tests in chrome (also works on Safari)
One reason I have seen that the tests do not work is sometimes you gave to try http://localhost:8080/debug?port=5858 or http://127.0.0.1:8080/debug?port=5858
Solution 5:[5]
run mocha with flag --inspect-brk and click 'open dedicated DevTools for node' in chrome from page chrome://inspect. In dedicated DevTools window add connection localhost:9229 to connect automatically.
Also add a debugger statement to the file you want debug.
(this is using latest versions of node and chrome as of October 2017)
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow
| Solution | Source |
|---|---|
| Solution 1 | ELLIOTTCABLE |
| Solution 2 | |
| Solution 3 | Matthew Shanley |
| Solution 4 | Trideep Gogoi |
| Solution 5 |