diff --git a/test/external_pair.jl b/test/external_pair.jl
index 9fb18ce..950d1cc 100644
--- a/test/external_pair.jl
+++ b/test/external_pair.jl
@@ -1,8 +1,8 @@
 using LAMMPS
 using Test
 
-lmp_native = LMP()
-lmp_julia = LMP()
+lmp_native = LMP(["-screen", "none"])
+lmp_julia = LMP(["-screen", "none"])
 
 for lmp in (lmp_native, lmp_julia)
     command(lmp, "units lj")
@@ -24,13 +24,13 @@ command(lmp_julia, "fix julia_lj all external pf/callback 1 1")
 command(lmp_native, "pair_style lj/cut $cutoff")
 command(lmp_native, "pair_coeff * * 1 1")
 
-const coefficients = Dict(
-    1 => Dict(
-        1 => [48.0, 24.0, 4.0,4.0]
+const coefficients = Base.ImmutableDict(
+    1 => Base.ImmutableDict(
+        1 => [48.0, 24.0, 4.0, 4.0]
     )
 )
 
-function compute_force(rsq, itype, jtype)
+@inline function compute_force(rsq, itype, jtype)
     coeff = coefficients[itype][jtype]
     r2inv  = 1.0/rsq
     r6inv  = r2inv^3
@@ -39,7 +39,7 @@ function compute_force(rsq, itype, jtype)
     return (r6inv * (lj1*r6inv - lj2))*r2inv
 end
 
-function compute_energy(rsq, itype, jtype)
+@inline function compute_energy(rsq, itype, jtype)
     coeff = coefficients[itype][jtype]
     r2inv  = 1.0/rsq
     r6inv  = r2inv^3
@@ -58,14 +58,14 @@ for lmp in (lmp_native, lmp_julia)
     command(lmp, "create_atoms 1 random $natoms 1 NULL")
     command(lmp, "mass 1 1.0")
 
-    LAMMPS.API.lammps_scatter_atoms(lmp, "x", 1, 3, positions)
+    scatter!(lmp, "x", positions)
 
     command(lmp, "run 0")
 end
 
 # extract forces
-forces_native = extract_atom(lmp_native, "f")
-forces_julia = extract_atom(lmp_julia, "f")
+forces_native = gather(lmp_native, "f", Float64)
+forces_julia = gather(lmp_julia, "f", Float64)
 
 @testset "External Pair" begin
     @test forces_native == forces_julia