refactor: change from standar backend api to python library

tests/test_join_corresponding_sums.py

@@ -0,0 +1,48 @@
+import unittest
+
+from math_problems_structure.grade_1 import join_corresponding_sums
+
+
+class JoinCorrespondingSumsTest(unittest.TestCase):
+    def test_creates_problem_with_matching_sums(self) -> None:
+        problem = join_corresponding_sums(pair_count=3, seed=1)
+
+        self.assertEqual(problem["instructions"], "Conecta.")
+        self.assertEqual(len(problem["left_expressions"]), 3)
+        self.assertEqual(len(problem["right_expressions"]), 3)
+        self.assertEqual(len(problem["answer_key"]), 3)
+
+        left_by_position = {
+            expression["position"]: expression
+            for expression in problem["left_expressions"]
+        }
+        right_by_position = {
+            expression["position"]: expression
+            for expression in problem["right_expressions"]
+        }
+
+        for expression in problem["left_expressions"] + problem["right_expressions"]:
+            self.assertEqual(
+                expression["first_addend"] + expression["second_addend"],
+                expression["total"],
+            )
+
+        for connection in problem["answer_key"]:
+            left_expression = left_by_position[connection["left_position"]]
+            right_expression = right_by_position[connection["right_position"]]
+
+            self.assertEqual(left_expression["total"], right_expression["total"])
+            self.assertEqual(left_expression["total"], connection["total"])
+            self.assertEqual(left_expression["match_id"], right_expression["match_id"])
+            self.assertEqual(left_expression["match_id"], connection["match_id"])
+
+    def test_raises_for_impossible_ranges(self) -> None:
+        with self.assertRaisesRegex(
+            ValueError,
+            "sum and addend ranges must contain enough matchable sums",
+        ):
+            join_corresponding_sums(pair_count=3, min_sum=2, max_sum=2)
+
+
+if __name__ == "__main__":
+    unittest.main()