Rationale
Aiming at coverage, for coverage's sake is a bad practice. Test should use assertions properly, to ensure logic works as expected in all the relevant circumstances.
Configuration
Minimum number of assertions. The number of assertions that you need to be present on each test method. Any number below this threshold will trigger a detection.
Scope
Apex test methods that don't contain sufficient number of System.assert or equivalent
Using FinancialForce's ApexMock library
Invocations of the fflib_ApexMocks.verify method are treated as valid assertions by this rule.
// Given
fflib_ApexMocks mocks = new fflib_ApexMocks();
fflib_MyList.IList mockList = (fflib_MyList.IList)mocks.mock(fflib_MyList.class);
// When
mockList.add('bob');
// Then
((fflib_MyList.IList) mocks.verify(mockList)).add('bob');
((fflib_MyList.IList) mocks.verify(mockList, fflib_ApexMocks.NEVER)).clear();