diff --git a/tests/test_parser.py b/tests/test_parser.py
index 2d4117a..2219722 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -137,3 +137,22 @@ def test_compile_to_constraints_picklable():
             assert callable(r)
         else:
             assert isinstance(r, expected)
+
+def test_compile_non_numeric():
+    domains = {"x": ["a2", "b4", "c6"], "y": [True, False]}
+    constraints = [
+        "x == 'a'", 
+        "y == 'd' or x != 'b'", 
+        "'a' <= x + y < 'c'"
+    ]
+    
+    compiled = compile_to_constraints(constraints, domains, picklable=False)
+    
+    assert len(compiled) == 4
+    for r, vals, r_str in compiled:
+        assert isinstance(r, (Constraint, CompilableFunctionConstraint))
+        assert isinstance(vals, Iterable) and all(isinstance(v, str) for v in vals)
+        if isinstance(r, (FunctionConstraint, CompilableFunctionConstraint)):
+            assert isinstance(r_str, str)
+        else:
+            assert r_str is None
diff --git a/tests/test_solvers.py b/tests/test_solvers.py
index adc4c31..2698537 100644
--- a/tests/test_solvers.py
+++ b/tests/test_solvers.py
@@ -94,7 +94,7 @@ def test_parallel_solver():
     order = ["x", "y"]
 
     # get all solutions
-    solutions_list, solutions_dict, size = problem.getSolutionsAsListDict(order=order)
+    solutions_list, _, size = problem.getSolutionsAsListDict(order=order)
 
     # validate all solutions
     assert size == len(true_solutions)
@@ -120,7 +120,7 @@ def test_parallel_solver_process_mode():
     order = ["x", "y"]
 
     # get all solutions
-    solutions_list, solutions_dict, size = problem.getSolutionsAsListDict(order=order)
+    solutions_list, _, size = problem.getSolutionsAsListDict(order=order)
 
     # validate all solutions
     assert size == len(true_solutions)
@@ -175,4 +175,32 @@ def create_problem(solver):
                 base_solution = solutions_list
             else:
                 assert size == len(base_solution)
-                # assert all(sol in solutions_list for sol in base_solution)
\ No newline at end of file
+                # assert all(sol in solutions_list for sol in base_solution)
+
+def test_mixed_type_constraints():
+    """Test that mixed type constraints are handled correctly."""
+    problem = Problem()
+    domains = {"x": ["a", "b", "c"], "y": [True, False], "z": [0, 1]}
+    for var, domain in domains.items():
+        problem.addVariable(var, domain)
+    constraints = [
+        "x != 'a' or y < z", 
+        "y or x != 'b'",
+    ]
+    problem.addConstraint(constraints)
+    solutions, _, _ = problem.getSolutionsAsListDict(order=list(domains.keys()))
+    
+    possible_solutions = [
+        ('c', False, 1), 
+        ('c', False, 0), 
+        ('a', False, 1), 
+        ('b', True, 0), 
+        ('b', True, 1), 
+        ('c', True, 0), 
+        ('c', True, 1)
+    ]
+
+    assert len(solutions) == len(possible_solutions), "Number of solutions does not match expected"
+    assert len(set(solutions)) == len(possible_solutions), "Number of unique solutions does not match expected"
+    for solution in solutions:
+        assert solution in possible_solutions, f"Unexpected solution: {solution}"