fix test for specrtum area as a fn of sidebands

fix bug cause spectral area to change as counts change.

CHANGELOG

@@ -27,6 +27,8 @@ Bug fixes
 
 - Fixed bug resulting from the rotation of the fourth rank tensor with non-zero euler
   angles.
+- Fixed bug causing a change in the spectral area as the sampling points change. Now the
+  area is constant.
 
 Other changes
 '''''''''''''

src/c_lib/base/base_model.pyx

@@ -179,6 +179,8 @@ def one_d_spectrum(method,
         &incre[0], &magnetic_flux_density_in_T[0], &srfiH[0],
         &rair[0], &n_event[0], n_sequence, number_of_sidebands)
 
+# normalization factor for the spectrum
+    norm = np.prod(incre)
 
 # create fftw scheme __________________________________________________________
 
@@ -386,7 +388,7 @@ def one_d_spectrum(method,
                     interpolation,
                     )
 
-            temp = amp*abundance
+            temp = amp*abundance/norm
 
             ## reverse the spectrum if gyromagnetic ratio is positive.
             if gyromagnetic_ratio < 0:

src/mrsimulator/__init__.py

@@ -15,7 +15,7 @@
 See https://mrsimulator.readthedocs.io/en/stable/ for complete documentation.
 """
 # version has to be specified at the start.
-__version__ = "0.3.0a1"
+__version__ = "0.3.0a2"
 
 from .spin_system import Site  # lgtm [py/import-own-module]
 from .spin_system import SpinSystem  # lgtm [py/import-own-module]

tests/test_amplitude.py

@@ -80,7 +80,7 @@ def test_with_configuration_setting():
         err_msg="Integral error from νr, integration density, integration volume.",
     )
 
-    sim.methods[0].spectral_dimensions[0].count = 256
+    sim.config.number_of_sidebands = 256
     sim.run()
     y_spinning_MAS_1 = sim.methods[0].simulation.dependent_variables[0].components[0]
 
@@ -97,14 +97,17 @@ def test_number_of_points():
     sim.methods[0].spectral_dimensions[0].count = 2048
     sim.run()
     y_static = sim.methods[0].simulation.dependent_variables[0].components[0]
+    inc = sim.methods[0].simulation.dimensions[0].increment.to("Hz").value
 
     sim.methods[0].spectral_dimensions[0].count = 4096
     sim.run()
     y_static_1 = sim.methods[0].simulation.dependent_variables[0].components[0]
+    inc_1 = sim.methods[0].simulation.dimensions[0].increment.to("Hz").value
 
+    print(inc, inc_1)
     np.testing.assert_almost_equal(
-        y_static.sum(),
-        y_static_1.sum(),
+        y_static.sum() * inc,
+        y_static_1.sum() * inc_1,
         decimal=8,
         err_msg="Integral error from number_of_points",
     )