The invention is an assembly which is run into the wellbore to straddle pre-existing control line connections used normally for actuation of a sleeve for a single subsurface safety valve. The lower flapper is closed through the use of one of the control lines. It is then tested against formation pressure to make sure that it holds. Upon determination that the lower flapper is holding, the upper flapper is shut off using the other control line. By adding additional pressure to the control line for the lower sleeve, further movement of the lower sleeve is obtained to urge another sleeve into contact with the upper flapper to provide support for it so that it can be tested from above. Once the two flappers have been tested, uphole assembly in the wellbore can begin through the wellhead in the zone above the tested valves once assembled. Coiled tubing or wireline can be advanced sealingly through the wellhead as the assembly is lowered past the flappers which are now allowed to open. The flapper assembly is eventually removed.