summary
As rarely used as it is, Mocha currently supports marking a test as failed after it has already completed.

As an example, here is a unit test from mocha's own suite (src):

describe('fail the test from the "after each" hook', function() { 
   it('should fail', function() { 
     // but not here 
   }); 
  
   afterEach(function() { 
     this.test.error(new Error('failing from after each')); 
   }); 
 }); 

This code branch needs to call karma.report in the case of test.type === 'test':

Is this something maintainers would be willing to accept a PR on?

Thanks!