diff --git a/test/SummationByPartsOperatorsExt_tests.jl b/test/SummationByPartsOperatorsExt_tests.jl
index 50276cf9..90ad63b3 100644
--- a/test/SummationByPartsOperatorsExt_tests.jl
+++ b/test/SummationByPartsOperatorsExt_tests.jl
@@ -1,25 +1,25 @@
-@testset "StartUpDGSummationByPartsOperatorsExt tests" begin
 
+@testset "SummationByPartsOperators ext tests for nonperiodic operators" begin
     tol = 200*eps()
-
     N = 3
     f(N,r,s) = r^N + s^N # function for testing differentiation
-    
+
     D = derivative_operator(MattssonNordström2004(), 
                             derivative_order=1, accuracy_order=N+1,
                             xmin=-1.0, xmax=1.0, N=20)
-
     @testset "Line" begin
-        rd = RefElemData(Quad(), D)
+        rd = RefElemData(Line(), D)
         @test rd.r == rd.rst[1]
         @test rd.Np == length(rd.r)  
         @test rd.Nq == length(rd.rq)    
-        @test abs(sum(rd.wq)) ≈ 4
-        @test abs(sum(rd.wf)) ≈ 8
-        @test abs(sum(rd.wf .* rd.nrJ)) + abs(sum(rd.wf .* rd.nsJ)) < tol
+        @test abs(sum(rd.wq)) ≈ 2
+        @test abs(sum(rd.wf .* rd.nrJ)) < tol
         @test rd.Pq*rd.Vq ≈ I
         @test all(vec.(rd.rstf) .≈ (x->getindex(x,rd.Fmask)).(rd.rst))
         @test StartUpDG.eigenvalue_inverse_trace_constant(rd) ≈ inverse_trace_constant(rd)    
+
+        md = MeshData(uniform_mesh(Line(), 2), rd)
+        @test estimate_h(1, rd, md) ≈ 0.5
     end
 
     @testset "Quad" begin
@@ -55,4 +55,59 @@
         @test StartUpDG.eigenvalue_inverse_trace_constant(rd) ≈ inverse_trace_constant(rd)
     end
 
+end
+
+@testset "SummationByPartsOperators ext tests for periodic operators" begin
+    tol = 200*eps()
+    N = 3
+    D = periodic_derivative_operator(derivative_order=1, accuracy_order=N+1,
+                                     xmin=0.0, xmax=2.0, N=20)
+
+    @testset "Line" begin
+        rd = RefElemData(Line(), D)
+        @test rd.r == rd.rst[1]
+        @test rd.Np == length(rd.r)  
+        @test rd.Nq == length(rd.rq)    
+        @test abs(sum(rd.wq)) ≈ 2
+
+        # diff matrices should be skew symmetric
+        Qrst = (A -> rd.M * A).(rd.Drst)
+        @test all((A -> norm(A+A')).(Qrst) .< tol)
+
+        @test rd.Pq*rd.Vq ≈ I
+
+    end
+
+    @testset "Quad" begin
+        rd = RefElemData(Quad(), D)
+        @test rd.r == rd.rst[1]
+        @test rd.Np == length(rd.r)  
+        @test rd.Nq == length(rd.rq)    
+        @test abs(sum(rd.wq)) ≈ 4
+
+        # diff matrices should be skew symmetric
+        Qrst = (A -> rd.M * A).(rd.Drst)
+        @test all((A -> norm(A+A')).(Qrst) .< tol)
+
+        @test rd.Pq*rd.Vq ≈ I
+    end
+    
+    @testset "Hex" begin
+        rd = RefElemData(Hex(), D)
+        @test propertynames(rd)[1] == :element_type
+        @test rd.t == rd.rst[3]
+        @test rd.tq == rd.rstq[3]
+        @test rd.rp == rd.rstp[1]    
+        @test rd.sp == rd.rstp[2]
+        @test rd.tp == rd.rstp[3]    
+        @test rd.Np == length(rd.r)  
+        @test rd.Nq == length(rd.rq)    
+        @test abs(sum(rd.wq)) ≈ 8
+        
+        # diff matrices should be skew symmetric
+        Qrst = (A -> rd.M * A).(rd.Drst)
+        @test all((A -> norm(A+A')).(Qrst) .< tol)
+
+        @test rd.Pq*rd.Vq ≈ I
+    end
 end
\ No newline at end of file