add basic tests

code/tests/test_energy.py

@@ -0,0 +1,27 @@
+import numpy as np
+from matplotlib.image import imread
+from pathlib import Path
+
+from MCFF.ising_model import all_up_state, all_down_state, random_state
+from MCFF.ising_model import energy, energy_numpy
+
+# create some test states
+all_up = np.ones([100,100])
+all_down = -np.ones([100,100])
+random = np.random.choice([-1, 1], size = (100,100))
+custom = (1 - 2*imread(Path(__file__).parents[2]/'learning/data/test_state.png')[:, :, 0]) #load a 100x100 png, take the red channel, remap 0,1 to -1,1
+
+states = [all_up, all_down, random, custom]
+
+def E_prediction_all_the_same(L):
+    "The exact energy in for the case where all spins are up or down"
+    return -(4*(L - 2)**2 + 12*(L-2) + 8) / L**2
+
+def test_exact_energies():
+    for state in [all_up, all_down]:
+        L = state.shape[0]
+        assert energy(state) == E_prediction_all_the_same(L)
+
+def test_energy_implementations():
+    for state in states:
+        assert np.allclose(energy(state), energy_numpy(state))