In COBOL, the default testing method for a PERFORM statement is "TEST BEFORE."
With "TEST BEFORE," the condition specified in the PERFORM statement is evaluated before entering the loop. If the condition is true, the loop's body is executed, and the loop continues to execute as long as the condition remains true. Once the condition evaluates to false, the loop terminates, and the program proceeds to the next statement after the PERFORM.
It's essential to keep in mind that if you want to change the default testing method to "TEST AFTER," you need to explicitly specify it in the PERFORM statement using the "WITH TEST AFTER" clause. Otherwise, the compiler will assume "TEST BEFORE" by default.