Build typed IPython app execution pipeline

tests/test_app.py

@@ -0,0 +1,58 @@
+import contextlib
+import io
+import json
+import subprocess
+import sys
+import unittest
+
+from ipython_demo.app import App
+from ipython_demo.models import CallResponse
+
+
+class AppTests(unittest.TestCase):
+    def test_main_emits_one_json_payload(self):
+        completed = subprocess.run(
+            [sys.executable, "-c", "from ipython_demo.app import main; main()"],
+            capture_output=True,
+            text=True,
+            check=True,
+        )
+
+        payload = json.loads(completed.stdout)
+        self.assertEqual(len(payload), 2)
+        self.assertEqual(payload[0]["events"][0]["kind"], "stdout")
+        self.assertTrue(payload[1]["collapsed"])
+
+    def test_run_code_returns_frontend_facing_call_response(self):
+        app = App()
+
+        with contextlib.redirect_stdout(io.StringIO()):
+            call = app.run_code(
+                "print('hello'); 2 + 2",
+                shell_name="new",
+                collapsed=True,
+            )
+
+        self.assertIsInstance(call, CallResponse)
+        self.assertEqual(call.code, "print('hello'); 2 + 2")
+        self.assertTrue(call.collapsed)
+        self.assertEqual(call.result.result, 4)
+        self.assertEqual([event.kind for event in call.events], [
+            "stdout",
+            "execute_result",
+        ])
+
+    def test_last_reuses_shell_but_each_call_has_new_id(self):
+        app = App()
+
+        with contextlib.redirect_stdout(io.StringIO()):
+            first = app.run_code("x = 41", shell_name="new")
+            second = app.run_code("x + 1", shell_name="last")
+
+        self.assertEqual(first.shell_name, second.shell_name)
+        self.assertNotEqual(first.call_id, second.call_id)
+        self.assertEqual(second.result.result, 42)
+
+
+if __name__ == "__main__":
+    unittest.main()