sum of iterable post hook (#251)

* added in sum of iterable post hook
* linted

spock/utils.py

@@ -12,6 +12,7 @@
 import sys
 from argparse import _ArgumentGroup
 from enum import EnumMeta
+from math import isclose
 from pathlib import Path
 from time import localtime, strftime
 from typing import Any, Dict, List, Tuple, Type, TypeVar, Union
@@ -54,15 +55,15 @@ def _get_callable_type():
 _C = TypeVar("_C", bound=type)
 
 
-def eq_len(val: List[Union[Tuple, List, None]], allow_optional: bool = True):
-    """Checks that all values passed in the iterable are of the same length
+def _filter_optional(val: List, allow_optional: bool = True):
+    """Filters an iterable for None values if they are allowed
 
     Args:
-        val: iterable to compare lengths
+        val: iterable of values that might contain None
         allow_optional: allows the check to succeed if a given val in the iterable is None
 
     Returns:
-        None
+        filtered list of values with None values removed
 
     Raises:
         _SpockValueError
@@ -76,6 +77,54 @@ def eq_len(val: List[Union[Tuple, List, None]], allow_optional: bool = True):
             )
         elif v is not None:
             filtered_val.append(v)
+    return filtered_val
+
+
+def sum_vals(
+    val: List[Union[float, int, None]],
+    sum_val: Union[float, int],
+    allow_optional: bool = True,
+    rel_tol: float = 1e-9,
+    abs_tol: float = 0.0,
+):
+    """Checks if an iterable of values sums within tolerance to a specified value
+
+    Args:
+        val: iterable of values to sum
+        sum_val: sum value to compare against
+        allow_optional: allows the check to succeed if a given val in the iterable is None
+        rel_tol: relative tolerance – it is the maximum allowed difference between a and b
+        abs_tol: the minimum absolute tolerance – useful for comparisons near zero
+
+    Returns:
+        None
+
+    Raises:
+        _SpockValueError
+
+    """
+    filtered_val = _filter_optional(val, allow_optional)
+    if not isclose(sum(filtered_val), sum_val, rel_tol=rel_tol, abs_tol=abs_tol):
+        raise _SpockValueError(
+            f"Sum of iterable is `{sum(filtered_val)}` which is not equal to specified value `{sum_val}` within given tolerances"
+        )
+
+
+def eq_len(val: List[Union[Tuple, List, None]], allow_optional: bool = True):
+    """Checks that all values passed in the iterable are of the same length
+
+    Args:
+        val: iterable to compare lengths
+        allow_optional: allows the check to succeed if a given val in the iterable is None
+
+    Returns:
+        None
+
+    Raises:
+        _SpockValueError
+
+    """
+    filtered_val = _filter_optional(val, allow_optional)
     # just do a set comprehension -- iterables shouldn't be that long so pay the O(n) price
     lens = {len(v) for v in filtered_val}
     if len(lens) != 1:

tests/base/test_post_hooks.py

@@ -8,7 +8,7 @@
 
 from spock import spock
 from spock import SpockBuilder
-from spock.utils import within, gt, ge, lt, le, eq_len
+from spock.utils import within, gt, ge, lt, le, eq_len, sum_vals
 from spock.exceptions import _SpockInstantiationError
 
 
@@ -130,8 +130,60 @@ def __post_hook__(self):
         eq_len([self.val_1, self.val_2, self.val_3], allow_optional=True)
 
 
+@spock
+class SumNoneFailConfig:
+    val_1: float = 0.5
+    val_2: float = 0.5
+    val_3: Optional[float] = None
+
+    def __post_hook__(self):
+        sum_vals([self.val_1, self.val_2, self.val_3], sum_val=1.0, allow_optional=False)
+
+
+@spock
+class SumNoneNotEqualConfig:
+    val_1: float = 0.5
+    val_2: float = 0.5
+    val_3: Optional[float] = None
+
+    def __post_hook__(self):
+        sum_vals([self.val_1, self.val_2, self.val_3], sum_val=0.75)
+
+
 class TestPostHooks:
 
+    def test_sum_none_fail_config(self, monkeypatch, tmp_path):
+        """Test serialization/de-serialization"""
+        with monkeypatch.context() as m:
+            m.setattr(
+                sys,
+                "argv",
+                [""],
+            )
+            with pytest.raises(_SpockInstantiationError):
+                config = SpockBuilder(
+                    SumNoneFailConfig,
+                    desc="Test Builder",
+                )
+                config.generate()
+
+    def test_sum_not_equal_config(self, monkeypatch, tmp_path):
+        """Test serialization/de-serialization"""
+        with monkeypatch.context() as m:
+            m.setattr(
+                sys,
+                "argv",
+                [""],
+            )
+            with pytest.raises(_SpockInstantiationError):
+                config = SpockBuilder(
+                    SumNoneNotEqualConfig,
+                    desc="Test Builder",
+                )
+                config.generate()
+
+
+
     def test_eq_len_two_len_fail(self, monkeypatch, tmp_path):
         """Test serialization/de-serialization"""
         with monkeypatch.context() as m: