Running the flow using it to create contacts and using debug to test the flow in Flow Builder are two key components of testing a new screen flow that creates contacts. Running the flow allows the administrator to see how the flow behaves in real time and check for any errors or unexpected results. Debugging the flow allows the administrator to simulate how the flow runs with different inputs and outputs and check for any logic or syntax errors. Setting up a flow interview or testing the flow in a sandbox are not necessary for testing a screen flow that creates contacts.References: https://help.salesforce.com/s/articleView?id=sf.
flow_test.htm&type=5