Can any evidence be marshaled or any argument made which would cause you to conclude that Scrum is not valuable?
If you answer yes, then you have a testable belief in the value of Scrum. If no, then you have a non-testable belief in the value of Scrum.
I note that here is nothing inappropriate, incorrect or shameful about holding non-testable beliefs. I have a non-testable belief that my family loves me.
Knowing whether your belief in Scrum is testable or not can be useful. If I have a non-testable belief in Scrum then when a client asks me to provide data about the utility of Scrum I might say, “I am happy to do that. Know, however, that there is no evidence which will cause me to change my belief in the value of Scrum.”
If my belief in Scrum were testable, I might dedicate some time to looking for evidence that would cause me to conclude that Scrum does not work. If I find this evidence, then I might choose to stop being a Scrum consultant.
A second reason to think about the testability of your belief is that it might inform your discussions with other Scrum aficionados. A person with a testable belief in Scrum might say, “I analyzed 23 companies that used 6 approaches and Scrum was 45.3% better than the second best approach.” If you wanted to disagree with this person and argue, say, that Kanban is better, then you might present evidence that Kanban is 4.5% better than Scrum.
In contrast, a person with a non-testable belief in Scrum might say, “I have certain principles and values, and I view Scrum as a way of living these principles and values in the workplace.” Such a person would probably completely decline a Scrum vs. Kanban analysis. If your belief in Scrum’s value is testable, what kind of evidence or argument would cause you to conclude that Scrum is not valuable?