Enhance documentation and test coverage for options handling

Co-authored-by: mballance <1340805+mballance@users.noreply.github.com>

Author: Copilot

src/vsc/coverage.py

@@ -907,7 +907,17 @@ def __init__(self,
                  ignore_bins=None):
         # Recursively flatten nested crosses by extracting their coverpoints
         def flatten_targets(targets):
-            """Recursively flatten a list of coverpoints and crosses."""
+            """Recursively flatten a list of coverpoints and crosses.
+            
+            Args:
+                targets: List of coverpoint and/or cross objects
+                
+            Returns:
+                List of coverpoint objects (flat list with all crosses expanded)
+                
+            Raises:
+                Exception: If any target is neither a coverpoint nor a cross
+            """
             flattened = []
             for t in targets:
                 if isinstance(t, cross):

ve/unit/test_coverage_cross.py

@@ -183,17 +183,33 @@ def __init__(self):
                 self.cross_ab = vsc.cross([self.cp_a, self.cp_b])
 
                 # Nested cross with options
-                self.cross_abc = vsc.cross(
+                self.cross_abc_nested = vsc.cross(
                     [self.cross_ab, self.cp_c],
                     options=dict(at_least=2)
                 )
+                
+                # Non-nested cross with same options for comparison
+                self.cross_abc_flat = vsc.cross(
+                    [self.cp_a, self.cp_b, self.cp_c],
+                    options=dict(at_least=2)
+                )
 
         cg = nested_cross_options_cg()
         cg.sample(10, 20, 30)
 
-        # Verify structure
-        self.assertEqual(len(cg.cross_abc.target_l), 3)
-        # Verify options were set correctly
-        self.assertIsNotNone(cg.cross_abc.options)
-        self.assertEqual(cg.cross_abc.options.at_least, 2)
+        # Verify structure of nested cross
+        self.assertEqual(len(cg.cross_abc_nested.target_l), 3)
+        # Verify options were set correctly on nested cross
+        self.assertIsNotNone(cg.cross_abc_nested.options)
+        self.assertEqual(cg.cross_abc_nested.options.at_least, 2)
+        
+        # Verify structure of flat cross
+        self.assertEqual(len(cg.cross_abc_flat.target_l), 3)
+        # Verify options were set correctly on flat cross
+        self.assertIsNotNone(cg.cross_abc_flat.options)
+        self.assertEqual(cg.cross_abc_flat.options.at_least, 2)
+        
+        # Verify both crosses have same structure (proving flattening works correctly)
+        for i in range(3):
+            self.assertEqual(cg.cross_abc_nested.target_l[i], cg.cross_abc_flat.target_l[i])