Bessel Basis Unit Test. Present file will be read as C4 coefficients stored file of atom type 0. INPUTS tag: In INPUTS tag what enclosed are EnergyCutoff, CutoffRadius, Nq, Tolerance, respectively. They should be totally identical with function Bessel_Basis::init_Faln(), or assert() will fail. C4 tag: The first line of this tag will be the total chi. The chi acts similarly with contracted Gaussian type orbitals, which means for one chi, there will be Nq spherical Bessel functions, and for each angular momentum l, there will be numbers of chi-s to form it. C4 file contains all information of chi-s, i.e., all over l(s). For example the H, whose numerical orbitals file is named as H_gga_6au_100Ry_2s1p.orb, which means there are 3 kinds of orbitals, 1s, 2s and 2p. The cutoff radius is 6 au, and the energy cutoff is 100 Ry. For orbital "1s", there will be a chi_1s, then for "2s" the chi_2s, for "2p" the chi_2p, the first line is thus the number chi_1s + chi_2s + chi_2p. The following line has contents in sequence of: title1 title2 title3 AtomType AngularMomentum ChiIndex C4Vaule1 C4Value2 ... C4ValueNq Final description: In unit test case, only one chi, one l is used, and EnergyCutoff, CutoffRadius are selected to have Nq=1. 4 2 1 0.01 1 TEST TEST TEST 0 0 0 1.0