diff --git a/src/common.jl b/src/common.jl
index 1adf2dfb..450c6a6d 100644
--- a/src/common.jl
+++ b/src/common.jl
@@ -46,7 +46,7 @@ export AbstractBoundaryConditions,
 include("MiniKernels.jl")
 
 include("phases/phases.jl")
-export fn_ratio, phase_ratios_center!
+export fn_ratio, phase_ratios_center!, numphases, nphases
 
 include("rheology/BuoyancyForces.jl")
 export compute_ρg!
diff --git a/test/test_diffusion2D_multiphase.jl b/test/test_diffusion2D_multiphase.jl
index 52dea225..49ec80e7 100644
--- a/test/test_diffusion2D_multiphase.jl
+++ b/test/test_diffusion2D_multiphase.jl
@@ -193,19 +193,20 @@ function diffusion_2D(; nx=32, ny=32, lx=100e3, ly=100e3, Cp0=1.2e3, K0=3.0)
         t  += dt
     end
 
-    return thermal
+    return thermal, phase_ratios
 end
 
 @testset "Diffusion_2D_Multiphase" begin
     @suppress begin
         nx=32;
         ny=32;
-        thermal = diffusion_2D(; nx = nx, ny = ny)
+        thermal, phase_ratios = diffusion_2D(; nx = nx, ny = ny)
 
         nx_T, ny_T = size(thermal.T)
         if backend_JR === CPUBackend
             @test thermal.T[nx_T >>> 1 + 1, ny_T >>> 1 + 1] ≈ 1819.2297931741878 atol=1e-1
             @test thermal.Tc[ nx >>> 1    ,   nx >>> 1    ] ≈ 1824.3532934301472 atol=1e-1
+            @test nphases(phase_ratios)=== Val{2}()
         else
             @test true == true
         end
diff --git a/test/test_traits.jl b/test/test_traits.jl
index 93d0e090..2034a2ee 100644
--- a/test/test_traits.jl
+++ b/test/test_traits.jl
@@ -56,6 +56,7 @@ end
 
     # test PTArray
     @test PTArray(backend) === A
+    @test PTArray()        === A
     @test_throws ArgumentError PTArray(bk(rand()))
     @test_throws ArgumentError PTArray(bk("potato"))