SetDirectory["d:\\demopainlevetest"]

Get["PainleveTestV2.m"]

PainleveTest[{D[u[x, t],  t] + 
            6*u[x, t]^2*D[u[x, t], x] - (ff[t]*x + gg[t])*
              D[u[x, t],  x] - D[u[x, t],  {x, 3}] - hh[t]*u[x, t] == 
          0},  
u[x, t],  {x, t} ,  
      Verbose  ->  
        True    ]

PainleveTest[{D[u[x, t],  t] + 
            6*u[x, t]^2*D[u[x, t], x] - (ff[t]*x + gg[t])*
              D[u[x, t],  x] - D[u[x, t],  {x, 3}] - hh[t]*u[x, t] == 
          0},  
u[x, t],  {x, t} ,  
      Verbose  ->  
        True    ,  KruskalSimplification  ->  x ]