Fix issue where vacuum test tried to use barostat
@@ -391,7 +391,6 @@ class TestExternalPerturbationLangevinIntegrator(TestCase):
# Creating the test system with a high frequency barostat.
testsystem = testsystems.AlchemicalAlanineDipeptide(nonbondedMethod=getattr(app, nonbonded_method))
- testsystem.system.addForce(openmm.MonteCarloBarostat(1 * unit.atmospheres, temperature, 2))
context, integrator = self.create_system(testsystem, parameter_name, parameter_initial, temperature, platform_name)
# Number of NCMC steps
