Software is absolutely inadequate to prevent you from being distracted... You can block a couple of things but it's an uphill battle, because there are no limits to the number of things more interesting in the short term than writing unit tests.

It's import to identify and address the root of the problem rather than just the symptoms. Do you find your work rewarding? Will these unit tests help you to complete the goals you hold for yourself? Are you healthy enough to faciliate productive work?

Are you suggesting that people suffering from ADHD do not recognize that there is an issue?

Procrastination/lack of executive function is a symptom of ADHD.

Aren't these synonyms?

No, far from it. The pop culture definition of ADHD has become extremely vague and watered down, almost to the same degree that "OCD" has become a pop-culture term for attention to detail.

Procrastination is a common behavior in people with and without ADHD. Procrastination alone is not an indicator of ADHD.

Likewise, someone who procrastinates does not fully understand the struggles of someone with ADHD.