Add some tests

src/osipi/_tissue.py

@@ -401,7 +401,7 @@ def two_cxm(
         # Convolve impulse response with AIF
         convolution = np.convolve(ca, imp) * t[1]
 
-        ct = Fp * convolution
+        ct = Fp * convolution[0 : len(t)]
 
     else:
         # Resample at the smallest spacing

tests/test_tissue.py

@@ -125,11 +125,31 @@ def test_tissue_extended_tofts():
 
 
 def test_tissue_2compartment_model():
+    # 1. Basic operation of the function - test that the peak tissue
     t = np.arange(0, 6 * 60, 1, dtype=float)
     ca = osipi.aif_parker(t)
     ct = osipi.two_cxm(t, ca, E=0.15, Fp=0.2, Ve=0.2, Vp=0.3)
     assert np.round(np.max(ct)) < np.round(np.max(ca))
 
+    # 2. Basic operation of the function - test with non-uniform spacing of
+    t = np.geomspace(1, 6 * 60 + 1, num=360) - 1
+    ca = osipi.aif_parker(t)
+    ct = osipi.two_cxm(t, ca, E=0.15, Fp=0.2, Ve=0.2, Vp=0.3)
+    assert np.round(np.max(ct)) < np.round(np.max(ca))
+
+    # 3. The offset option - test that the tissue concentration is shifted
+    t = np.arange(0, 6 * 60, 1)
+    ca = osipi.aif_parker(t)
+    ct = osipi.two_cxm(t, ca, E=0.15, Fp=0.2, Ve=0.2, Vp=0.3, Ta=60.0)
+    assert (np.min(np.where(ct > 0.0)) - np.min(np.where(ca > 0.0)) - 1) * 1 == 60.0
+
+    # 4. Test that the area under the ct curve is approximately the sum of
+    # the extracellular volume and the plasma volume
+    t = np.arange(0, 6 * 60, 1)
+    ca = osipi.aif_parker(t)
+    ct = osipi.two_cxm(t, ca, E=0.15, Fp=0.2, Ve=0.2, Vp=0.3)
+    assert math.isclose(np.trapz(ct, t)/np.trapz(ca, t), 0.2 + 0.3, abs_tol=1e-1)
+
 
 if __name__ == "__main__":
     test_tissue_tofts()