diff --git a/TESTSUITE/combinedtests/cavity.m b/TESTSUITE/combinedtests/cavity.m
new file mode 100644
index 0000000..18310cb
--- /dev/null
+++ b/TESTSUITE/combinedtests/cavity.m
@@ -0,0 +1,152 @@
+function pass = cavity
+
+physical_constants;
+
+
+ENABLE_PLOTS = 1;
+CLEANUP = 0;        % if enabled and result is PASS, remove simulation folder
+STOP_IF_FAILED = 1; % if enabled and result is FAILED, stop with error
+
+% LIMITS
+upper_error = 0.036; % max +3.6%
+lower_error = 0;     % max -0.0%
+
+% structure
+a = 5e-2;
+b = 2e-2;
+d = 6e-2;
+if ~((b<a) && (a<d))
+    error 'correct the dimensions of the cavity'
+end
+
+f_start = 0;
+f_stop = 10e9;
+
+Sim_Path = 'tmp';
+Sim_CSX = 'cavity.xml';
+
+[status,message,messageid]=mkdir(Sim_Path);
+
+%setup FDTD parameter
+FDTD = InitFDTD( 10000,1e-6 );
+FDTD = SetGaussExcite(FDTD,(f_stop-f_start)/2,(f_stop-f_start)/2);
+BC = [0 0 0 0 0 0]; % PEC boundaries
+FDTD = SetBoundaryCond(FDTD,BC);
+
+%setup CSXCAD geometry
+CSX = InitCSX();
+mesh.x = linspace(0,a,35);
+mesh.y = linspace(0,b,35);
+mesh.z = linspace(0,d,35);
+CSX = DefineRectGrid(CSX, 1,mesh);
+
+% excitation
+pos1 = [mesh.x(10) mesh.y(10) mesh.z(10)];
+pos2 = [mesh.x(10) mesh.y(11) mesh.z(10)];
+CSX = AddExcitation(CSX,'excite',1,[0 1 0]);
+CSX = AddBox(CSX, 'excite', 1, pos1, pos2);
+ 
+% %dump
+% CSX = AddDump(CSX,'Et_',0,2);
+% pos1 = [mesh.x(1) mesh.y(10) mesh.z(1)];
+% pos2 = [mesh.x(end) mesh.y(10) mesh.z(end)];
+% CSX = AddBox(CSX,'Et_',0 , pos1,pos2);
+% 
+% %dump
+% CSX = AddDump(CSX,'Et2_',0,2);
+% pos1 = [mesh.x(1) mesh.y(1) mesh.z(1)];
+% pos2 = [mesh.x(end) mesh.y(1) mesh.z(end)];
+% CSX = AddBox(CSX,'Et2_',0 , pos1,pos2);
+% 
+% %dump
+% CSX = AddDump(CSX,'Et3_',0,2);
+% pos1 = [mesh.x(1) mesh.y(end-1) mesh.z(1)];
+% pos2 = [mesh.x(end) mesh.y(end-1) mesh.z(end)];
+% CSX = AddBox(CSX,'Et3_',0 , pos1,pos2);
+
+%voltage calc
+pos1 = [mesh.x(15) mesh.y(15) mesh.z(15)];
+pos2 = [mesh.x(15) mesh.y(16) mesh.z(15)];
+CSX = AddProbe(CSX,'ut1y',0);
+CSX = AddBox(CSX,'ut1y', 0 ,pos1,pos2);
+pos1 = [mesh.x(floor(end/2)) mesh.y(floor(end/2)) mesh.z(end)];
+pos2 = [mesh.x(floor(end/2)) mesh.y(floor(end/2)) mesh.z(end-1)];
+CSX = AddProbe(CSX,'ut1z',0);
+CSX = AddBox(CSX,'ut1z', 0 ,pos1,pos2);
+
+%Write openEMS compatible xml-file
+WriteOpenEMS([Sim_Path '/' Sim_CSX],FDTD,CSX);
+
+%cd to working dir and run openEMS
+savePath = pwd();
+cd(Sim_Path); %cd to working dir
+invoke_openEMS( Sim_CSX );
+UI = ReadUI( {'ut1x', 'ut1y', 'ut1z'} );
+cd(savePath);
+
+
+
+%
+% analysis
+%
+
+f = UI.FD{1}.f;
+ux = UI.FD{1}.val;
+uy = UI.FD{2}.val;
+uz = UI.FD{3}.val;
+
+f_idx_start = interp1( f, 1:numel(f), f_start, 'nearest' );
+f_idx_stop  = interp1( f, 1:numel(f), f_stop,  'nearest' );
+f = f(f_idx_start:f_idx_stop);
+ux = ux(f_idx_start:f_idx_stop);
+uy = uy(f_idx_start:f_idx_stop);
+uz = uz(f_idx_start:f_idx_stop);
+
+% analytic formula for resonant wavenumber
+k = @(m,n,l) sqrt( (m*pi/a)^2 + (n*pi/b)^2 + (l*pi/d)^2 );
+f_TE101 = c0/(2*pi) * k(1,0,1);
+f_TE102 = c0/(2*pi) * k(1,0,2);
+f_TE103 = c0/(2*pi) * k(1,0,3);
+f_TE201 = c0/(2*pi) * k(2,0,1);
+f_TE202 = c0/(2*pi) * k(2,0,2);
+f_TM110 = c0/(2*pi) * k(1,1,0);
+f_TM210 = c0/(2*pi) * k(2,1,0);
+
+f_TE = [f_TE101 f_TE102 f_TE103 f_TE201 f_TE202];
+f_TM = [f_TM110 f_TM210];
+
+if ENABLE_PLOTS
+    figure
+    plot(f/1e9,abs(uy))
+    max1 = max(abs(uy));
+    hold on
+    plot( repmat(f_TE,2,1)/1e9, repmat([0; max1],1,numel(f_TE)), 'm-.', 'LineWidth', 2 )
+    xlabel('Frequency (GHz)')
+    legend( {'u_y','theoretical'} );
+
+    figure
+    plot(f/1e9,abs(uz))
+    max1 = max(abs(uz));
+    hold on
+    plot( repmat(f_TM,2,1)/1e9, repmat([0; max1],1,numel(f_TM)), 'm-.', 'LineWidth', 2 )
+    xlabel('Frequency (GHz)')
+    legend( {'u_z','theoretical'} );
+end
+
+pass = 1;
+% pass = check_limits( Z, upper_limit, lower_limit );
+% if pass
+%     disp( 'combinedtests/Coax.m (characteristic impedance):  pass' );
+% else
+%     disp( 'combinedtests/Coax.m (characteristic impedance):  * FAILED *' );
+% end
+
+
+
+
+if pass && CLEANUP
+    rmdir( [Sim_Path '/' Sim_CSX], 's' );
+end
+if ~pass && STOP_IF_FAILED
+    error 'test failed';
+end