fix test

Author: isuruf

test/test_pde_system_utils.py

@@ -449,9 +449,10 @@ def test_int_gs_in_densities():
     result = merge_int_g_exprs([int_g1])
 
     source_kernels = [AxisSourceDerivative(0, laplace_knl), laplace_knl]
+
     densities = [
-        (-1)*int_g_vec(AxisTargetDerivative(1, laplace_knl),
-            density, qbx_forced_limit=1) * (-2),
+        (-1)*(int_g_vec(AxisTargetDerivative(1, laplace_knl),
+            density, qbx_forced_limit=1) * (-2)),
         int_g_vec(AxisTargetDerivative(2, laplace_knl),
             density, qbx_forced_limit=1) * (-1)
     ]