The level of logging by karma can be changed in the karma.conf.js file.

Go to karma.conf.js and add/change the property logLevel to config.LOG_DISABLE if you don't want to see any logs or config.LOG_ERROR if you want to only see the errors. Like this:

module.exports = function (config) {
  config.set({
    ...,
    logLevel: config.LOG_ERROR,
    ...,
  })
}

If you are running karma from the command line you can append --log-level debug to the command for the same effect.

Update for Angular version 9

The source files have been moved but you can still debug this way if you do the following steps

• In devtools, select the sources tab
• Press CTRL + P
• Type in the name of the file you want to debug

Valid for versions below 9

The other answers are completely valid answers but having been using Angular for around 18 months now I tend to do it in the browser - chrome tools!

Run ng test then f12 and find the spec file via the webpack context. Add a breakpoint(s) and refresh and it will hit said breakpoints. As per screenshot

I found a workaround for this. Create your custom logging.properties in src/test/resources, then in a setup call, load it up as such:

@BeforeClass(alwaysRun = true)
protected void setUp() throws SecurityException, IOException
{
    FileInputStream fis = new FileInputStream(BaseRestTest.class.getResource("/logging.properties").getFile());
    LogManager.getLogManager().readConfiguration(fis);
}

This appears to re-configure the root logger after TestNG has pillaged it.

Although you can't log dom/web events in the console that don't cause server requests, you can increase the amount of information that the compilation process and static web server provide by passing a --verbose flag when starting up: ng serve --verbose.

Also, if you're running a proxy a server to hit a local API server and you want some more logging regarding how those requests are being proxied, you can increase the logLevel in your proxy configuration.

Example proxy.conf.json:

{
    "/api": {
        "target": "http://localhost:3001",
        "secure": false,
        "logLevel": "debug"
    }
}

You would then be starting the server as ng serve --proxy-config proxy.conf.json --verbose.