[ntuple] Add more Python tests

tree/ntuple/v7/test/ntuple_basics.py

@@ -32,6 +32,63 @@ def test_write_read(self):
         self.assertEqual(entry["f"], 42)
         self.assertEqual(entry["mystr"], "string stored in RNTuple")
 
+    def test_write_fields(self):
+        """Can create writer with on-the-fly model"""
+
+        # FIXME: This should work without make_pair...
+        fields = [ROOT.std.make_pair("int", "f")]
+        with RNTupleWriter.Recreate(fields, "ntpl", "test_ntuple_py_write_fields.root") as writer:
+            entry = writer.CreateEntry()
+            entry["f"] = 42
+            writer.Fill(entry)
+
+        reader = RNTupleReader.Open("ntpl", "test_ntuple_py_write_fields.root")
+        self.assertEqual(reader.GetNEntries(), 1)
+        entry = reader.CreateEntry()
+        reader.LoadEntry(0, entry)
+        self.assertEqual(entry["f"], 42)
+
+    def test_append_open(self):
+        """Can append to existing TFile and open from RNTuple key."""
+
+        model = RNTupleModel.Create()
+        model.MakeField["int"]("f")
+
+        with ROOT.TFile.Open("test_ntuple_py_append.root", "RECREATE") as f:
+            with RNTupleWriter.Append(model, "ntpl", f) as writer:
+                entry = writer.CreateEntry()
+                entry["f"] = 42
+                writer.Fill(entry)
+        # The model should not have been destroyed (a clone has been used).
+        self.assertFalse(model.IsFrozen())
+
+        with ROOT.TFile.Open("test_ntuple_py_append.root") as f:
+            reader = RNTupleReader.Open(f["ntpl"])
+            self.assertEqual(reader.GetNEntries(), 1)
+            entry = reader.CreateEntry()
+            reader.LoadEntry(0, entry)
+            self.assertEqual(entry["f"], 42)
+
+    def test_read_model(self):
+        """Can impose a model when reading."""
+
+        write_model = RNTupleModel.Create()
+        write_model.MakeField["int"]("f1")
+        write_model.MakeField["int"]("f2")
+
+        with RNTupleWriter.Recreate(write_model, "ntpl", "test_ntuple_py_read_model.root") as writer:
+            entry = writer.CreateEntry()
+            writer.Fill(entry)
+
+        read_model = RNTupleModel.Create()
+        read_model.MakeField["int"]("f1")
+
+        reader = RNTupleReader.Open(read_model, "ntpl", "test_ntuple_py_read_model.root")
+        entry = reader.CreateEntry()
+        with self.assertRaises(Exception):
+            # Field f2 does not exist in imposed model
+            entry["f2"] = 42
+
     def test_forbid_writing_wrong_type(self):
         """Forbid writing the wrong type into an RNTuple field."""