🧪 Add error path testing for solve API endpoint

tests/test_app.py

@@ -0,0 +1,55 @@
+import sys
+from unittest.mock import MagicMock, patch
+
+# Mock inference module before importing app
+sys.modules['inference'] = MagicMock()
+
+import unittest
+from fastapi.testclient import TestClient
+from web.app import app
+import inference
+
+class TestApp(unittest.TestCase):
+    def setUp(self):
+        self.client = TestClient(app)
+        # Reset the mock before each test
+        inference.generate_solution.reset_mock()
+        inference.generate_solution.side_effect = None
+        inference.generate_solution.return_value = None
+
+    def test_ui_index(self):
+        response = self.client.get("/ui")
+        self.assertEqual(response.status_code, 200)
+
+    def test_root(self):
+        response = self.client.get("/")
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(
+            response.json(),
+            {"message": "OpenMath API. POST /solve with a problem to get a solution."}
+        )
+
+    def test_solve_empty_problem_error(self):
+        response = self.client.post("/solve", json={"problem": "  "})
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(response.json(), {"detail": "`problem` must be a non-empty string"})
+
+    def test_solve_success(self):
+        inference.generate_solution.side_effect = None
+        inference.generate_solution.return_value = "The solution is 2."
+
+        response = self.client.post("/solve", json={"problem": "1 + 1"})
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(response.json(), {"solution": "The solution is 2."})
+
+    def test_solve_error_path(self):
+        # Configure the mock to raise an exception
+        inference.generate_solution.side_effect = Exception("Mocked inference error")
+
+        response = self.client.post(
+            "/solve",
+            json={"problem": "1 + 1"},
+        )
+
+        self.assertEqual(response.status_code, 500)
+        self.assertEqual(response.json(), {"detail": "Mocked inference error"})