tests that wrapper rise error if invalid args

pyspectra/pyspectra.py

@@ -98,7 +98,7 @@ def eigensolver(
 
 
 def eigensolverh(
-        mat: np.ndarray, nvalues: int, selection_rule: str,
+        mat: np.ndarray, nvalues: int, selection_rule: Optional[str] = None,
         search_space: Optional[int] = None, generalized: np.ndarray = None,
         shift: Optional[Union[np.float, np.complex]] = None) -> EigenPair:
     """Compute ``nvalues`` eigenvalues for the symmetric matrix ``mat``.

tests/test_pyspectra.py

@@ -3,6 +3,7 @@
 from typing import Callable, List, Optional, Tuple, TypeVar, Union
 
 import numpy as np
+import pytest
 
 from pyspectra import eigensolver, eigensolverh
 
@@ -84,4 +85,21 @@ def test_eigensolverh():
 
     print(f"default search space and shift = {SIGMA.real}")
     run_test(eigensolverh, mat, nvalues, rules,
-             search_space=None, shift=SIGMA.real)
+             search_space=None, shift=SIGMA.real)
+
+
+def test_invalid_argument():
+    """Check that an error is raised if the arguments are invalid."""
+    mat = create_symmetic_matrix(SIZE)
+    nvalues = 2
+    print("wrong name for selection rule")
+    with pytest.raises(RuntimeError):
+        eigensolverh(mat, nvalues, selection_rule="Boom")
+
+    print("more eigenpairs requested than columns")
+    with pytest.raises(RuntimeError):
+        eigensolverh(mat, SIZE + 1)
+
+    print("Shift is not an scalar")
+    with pytest.raises(RuntimeError):
+        eigensolverh(mat, nvalues, shift="1.0")