Comment and do minor refactor

tests/test_compare_vcfs.py

@@ -99,17 +99,19 @@ def test_both_biallelic_same_alleles_different_order():
 def test_biallelic_monoallelic():
     ds1 = make_test_case()
     ds2 = ds1.copy(deep=True)
+    # At the first site, one allele is shared.
+    # At the second site, no allele is shared.
     for i in np.arange(ds2.variant_contig.size):
         ds2.variant_allele[i] = xr.DataArray([b'C', b''])
         ds2.call_genotype[i] = xr.DataArray(np.zeros_like(ds2.call_genotype[i]))
+    # Subtest 1
     actual = compare_vcfs.remap_genotypes(ds1, ds2)
-    # At the first site, one allele is shared.
-    # At the second site, no allele is shared.
     expected = [
         [[1, 1], [1, 1]],
         [[2, 2], [2, 2]],
     ]
     assert np.array_equal(actual, expected)
+    # Subtest 2
     actual = compare_vcfs.remap_genotypes(ds2, ds1)
     expected = [
         [[1, 0], [0, 1]],
@@ -121,18 +123,20 @@ def test_biallelic_monoallelic():
 def test_both_biallelic_different_alleles():
     ds1 = make_test_case()
     ds2 = ds1.copy(deep=True)
+    # At the first site, one allele is shared.
     ds2.variant_allele[0] = xr.DataArray([b'C', b'G'])
-    ds2.variant_allele[1] = xr.DataArray([b'A', b'C'])
     ds2.call_genotype[0] = xr.DataArray(data=[[0, 1], [1, 0]])
-    ds2.call_genotype[1] = xr.DataArray(data=[[0, 1], [1, 0]])
-    # At the first site, one allele is shared.
     # At the second site, no allele is shared.
+    ds2.variant_allele[1] = xr.DataArray([b'A', b'C'])
+    ds2.call_genotype[1] = xr.DataArray(data=[[0, 1], [1, 0]])
+    # Subtest 1
     actual = compare_vcfs.remap_genotypes(ds1, ds2)
     expected = [
         [[1, 2], [2, 1]],
         [[2, 3], [3, 2]],
     ]
     assert np.array_equal(actual, expected)
+    # Subtest 2
     actual = compare_vcfs.remap_genotypes(ds2, ds1)
     expected = [
         [[2, 0], [0, 2]],