927 Update tests for seed functions

#927

[author: carhc]

This PR updates some tests in
`invisible_cities/reco/krmap_functions_test.py` of PR 872.

[reviewer: gonzaponte]

Perfect! Good job.

invisible_cities/reco/krmap_functions_test.py

@@ -1,10 +1,10 @@
-import pytest
-
 import numpy          as np
 import numpy.testing  as npt
 import pandas         as pd
 import scipy.optimize as so
 
+from pytest                 import raises
+from pytest                 import fixture, mark
 from hypothesis             import given, settings
 from hypothesis.strategies  import floats, integers
 
@@ -18,7 +18,7 @@
        floats(min_value = 10, max_value = 20),
        floats(min_value = 1,  max_value = 100),
        floats(min_value = 0,  max_value = 10))
-def test_lin_function_output_values(x_min, x_max, a, b):
+def test_lin_seed_output_values(x_min, x_max, a, b):
     x = np.array([x_min, x_max])
     y = a + b * x
     a_test, b_test = krf.lin_seed(x, y)
@@ -27,6 +27,15 @@ def test_lin_function_output_values(x_min, x_max, a, b):
     assert np.isclose(b_test, b)
 
 
+def test_lin_seed_same_x_values():
+    x = np.ones(20)
+    y = np.ones(20) * 123
+    a_test, b_test = krf.lin_seed(x, y)
+
+    assert a_test == 123
+    assert b_test ==   0
+
+
 @given(floats(min_value = 1,    max_value = 10),
        floats(min_value = 1000, max_value = 1600),
        floats(min_value = 1e4,  max_value = 1e5),
@@ -40,7 +49,14 @@ def test_expo_seed_output_values(zmin, zmax, elt, e0):
     assert np.isclose(elt_test, elt, rtol=0.1)
 
 
-@pytest.fixture
+@mark.parametrize('y', ([-1, 1, 1, 1, 1], [1, 1, 1, 1, -1]))
+def test_expo_seed_negative_y_values(y):
+    x = np.ones(5)
+    with raises(ValueError, match = 'y data must be > 0'):
+        a_test, b_test = krf.expo_seed(x, y)
+
+
+@fixture
 def sample_df():
     data = {'DT' : [10, 20, 30, 40, 50],
             'S2e': [50, 45, 42, 41, 41]}