Question:

What is a clock test? 

Answer:

In the movie Brain on fire, Dr. Najjar asks Susannah Cahalan to draw the numbers on a clock face. She lists all 12 numbers of the clock – only on one side of the round face. That was how Dr. Najjar determined her condition was neurological.
To do the clock test, the instructions are for the person to draw a clock and put the hands at a specific time that the doctor says (usually it is 11:10). The clock test is used to assess the cognitive processes of:

• Executive functioning,
• Organization: Gathering information and structuring it for evaluation
• Regulation: Taking stock of your surroundings and changing behavior in response to it
• Global cognitive status,
• The mechanisms of how we learn, remember, problem-solve, and pay attention rather than actual knowledge.
• Visuospatial abilities,
• The ability to understand visual representations and their spatial relationships.
• Attention,
• The act or faculty of attending, especially by directing the mind to an object; concentrating.
• and Semantic knowledge
• General facts, meaning, ideas, and concepts that are not drawn from personal experience.

References:

Assessing Cognitive Impairment with a Clock Drawing Test