The full scale wind tunnel testing did not attempt to duplicate Martian conditions.
The purpose of the full scale testing was to to
provide an end to end test of the parachute system from
mortar fire to parachute inflation.
initial inflation strength qualification
Much more detail about subscale wind tunnel testing and other parachute tests can be found in the paper Overview of the Mars Science Laboratory Parachute Decelerator Subsystem. A sample:
a multi-phase delta qualification by analysis and subscale supersonic wind tunnel test program to address the fundamental
physics of the supersonic operation of DGB parachutes as a
function of Mach number , parachute size, and capsule wake
interaction. The first phase is computational fluid dynamics
(CFD) of a 2% scale rigid parachute canopy and capsule
validated by a 2% scale wind tunnel test of the rigid
configuration over the MSL Mach and Re number deployment
range in the Ames 9x7 ft. unitary tunnel. Phase two is
fluid structure interaction (FSI) analysis of a flexible
canopy with capsule validated by 5% scale wind tunnel tests
over the MSL deployment Mach and Re range in the GRC
10x 10 ft. unitary tunnel. The final phase is the
application of the validated FSI tools to the prediction of
the full scale para chute performance in Mars type deployment
conditions providing predictions of supersonic drag
performance, stability, and canopy loading.
DGB = Disk Gap Band