Can you be on test mode AND simulate test transactions while using the store as a customer?

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I tried to complete a transaction using the credit card test numbers on the live store as a customer vs as the admin of the store and it didn't work.  Only is the only way a test on a live store when you disable the test mode and use the testing credit card numbers?  As I would like members of my team to test out the store before we open it up to customers.