Index: test/sansmodels/test/core_shell_testdata.txt
===================================================================
--- test/sansmodels/test/core_shell_testdata.txt	(revision 5777106e8a4a0a62fe2ee0fbaf7c0aa19c0bb92b)
+++ test/sansmodels/test/core_shell_testdata.txt	(revision 5777106e8a4a0a62fe2ee0fbaf7c0aa19c0bb92b)
@@ -0,0 +1,138 @@
+pythonclass = CoreShellModel
+scale = 1
+radius = 60
+thickness = 10
+core_sld = 1e-6
+shell_sld = 2e-6
+solvent_sld = 3e-6
+background = 0.001
+
+DATA
+0.001	381.274046971472
+0.00105251266011778	381.237899910898
+0.00110778289970821	381.19786027418
+0.00116595552660488	381.153509293754
+0.00122718295288593	381.104383244174
+0.00129162559419317	381.049968637346
+0.00135945229002046	380.989696908168
+0.00143084074607265	380.922938539463
+0.00150597799985384	380.848996566762
+0.00158506091070502	380.767099400611
+0.00166829667557485	380.676392895334
+0.00175590337187494	380.575931589119
+0.00184811052884188	380.464669030575
+0.00194515972890305	380.341447101163
+0.00204730524062173	380.204984233923
+0.00215481468487986	380.053862419402
+0.00226796973604376	379.886512882077
+0.00238706685995004	379.701200298987
+0.00251241809064502	379.49600542349
+0.00264435184791283	379.268805965744
+0.00278321379773411	379.017255571336
+0.00292936775792964	378.738760728792
+0.00308319665136179	378.430455426155
+0.00324510350919104	378.08917336769
+0.00341551252681621	377.711417552685
+0.00359487017526494	377.293327011804
+0.00378364637094618	376.830640491906
+0.00398233570682956	376.318656879007
+0.00419145874827721	375.752192152612
+0.0044115633969232	375.125532673916
+0.00464322632617388	374.432384627427
+0.00488705449209019	373.665819462742
+0.0051436867236104	372.818215222885
+0.0054137953962797	371.881193701371
+0.00569808819387176	370.845553445896
+0.00599730996251769	369.701198727091
+0.00631224466220038	368.437064721844
+0.00664371742072679	367.041039329271
+0.00699259669556001	365.499882251454
+0.00735979654917468	363.799142240043
+0.00774627904389752	361.923073744821
+0.00815305676250721	359.854554613775
+0.00858119546119774	357.575007000233
+0.00903181686185589	355.064324247026
+0.00950610159096858	352.300807257296
+0.0100052922728602	349.261114744241
+0.010530696785364	345.920232795758
+0.0110836916864573	342.251470410986
+0.0116657258208385	338.226489077737
+0.0122783241158954	333.81537607021
+0.0129230915770094	328.986772953036
+0.0136017174926639	323.708072763327
+0.0143159798603742	317.945701467637
+0.0150677500450351	311.665501484756
+0.0158589976818897	304.833237213943
+0.0166917958369675	297.415244439261
+0.0175683264385096	289.379246945833
+0.0184908859936133	280.695364337768
+0.0194618916050726	271.337334425244
+0.0204838873041789	261.283971041376
+0.0215595507160742	250.520872986184
+0.0226917000751195	239.042391027563
+0.0238833016086589	226.853846399068
+0.0251374773085249	213.973974766497
+0.0264575131106459	200.437542879074
+0.027846867504187	186.298049862679
+0.0293091805927793	171.630380485316
+0.0308482836315787	156.533223593014
+0.0324682090651407	141.131006418686
+0.0341732010924115	125.57502775677
+0.035967726786514	110.043406138698
+0.0378564877984635	94.7394031434915
+0.0398444326754772	79.8876517594616
+0.0419367698261504	65.7278357602731
+0.0441389811664687	52.5054542084486
+0.0464568364824087	40.4594948569723
+0.0488964085467568	29.8071600221693
+0.0514640890297529	20.726258352271
+0.0541666052452436	13.336494524359
+0.0570110377762212	7.68161679902745
+0.0600048390259259	3.71512224140784
+0.0631558527431166	1.29279888095064
+0.0664723345726646	0.175550519014221
+0.0699629736853145	0.0453924538681532
+0.0736369155432808	0.535923418986669
+0.0775037858613269	1.27580609656724
+0.0815737158261042	1.93998544566538
+0.085857368639825	2.29923118349953
+0.0903659674578153	2.25545560606361
+0.0951113247931421	1.85001590113763
+0.100105873465356	1.23672780785815
+0.105362699174436	0.621355016508782
+0.110895574785276	0.183149542475723
+0.116718996412541	0.00639177282429009
+0.122848221400442	0.0529088860080835
+0.129299308296917	0.193331375536727
+0.136089158926978	0.285780213218503
+0.143235562675425	0.258850751719227
+0.150757243094979	0.144682310792552
+0.158673906961919	0.0362122531752963
+0.167006295907771	0.00113663058210361
+0.175776240762306	0.0277097331697254
+0.185006718750238	0.0531103329757048
+0.194721913691476	0.0401179463806756
+0.20494727936264	0.010881272301514
+0.215709606185875	0.0011822843814875
+0.227037091419654	0.00839678281024765
+0.238959413035505	0.00914771323458895
+0.251507807474183	0.00271488007246614
+0.264715151485044	0.00119017076116013
+0.278616048263005	0.00209189028269908
+0.2932469181088	0.00118078317349688
+0.308646093850034	0.00108286779061982
+0.324853921273063	0.00100867939845478
+0.341912864828804	0.00130885256583451
+0.359867618889456	0.00111691184987341
+0.378765224847594	0.00155107403368663
+0.398655194364451	0.00179962321843482
+0.4195896390903	0.00131961072539651
+0.441623407196792	0.00251915473759882
+0.464814227078974	0.00118345764149102
+0.489222858603482	0.0026873874933769
+0.514913252299177	0.00137597045735508
+0.541952716907305	0.00210439596198283
+0.570412095730168	0.00207013597449065
+0.600365952240318	0.00107370624743048
+0.631892765436603	0.00208956797079987
+0.665075135458861	0.00152395959676715
