If what we see in a case matches what we should see if explanation A was right and does not match what we should see if explanation B was right, then A is the best explanation
Negative case for the causes of genocide study: My theory Separatism based on ethic divisions feed genocide, Rule of Inclusion Colombia or Canada?, Rule of Exclusion Is Canada still a relevant negative case?
In "When Do the Dispossessed Protest?" Killian Clarke explores why refugees mobilize in some camps and not in others. Two of his cases are camps where refugees didn't mobilize.