Basic merge as versions view

src/documents/tests/test_merge_documents_as_versions.py

@@ -0,0 +1,67 @@
+from django.test import TestCase
+
+from documents.models import Document
+from documents.serialisers import MergeDocumentsAsVersionsSerializer
+
+
+class TestMergeDocumentsAsVersionsSerializer(TestCase):
+    def setUp(self) -> None:
+        self.doc1 = Document.objects.create(checksum="A", title="A")
+        self.doc2 = Document.objects.create(checksum="B", title="B")
+        self.doc3 = Document.objects.create(checksum="C", title="C")
+
+    def test_accepts_selected_root_document(self) -> None:
+        serializer = MergeDocumentsAsVersionsSerializer(
+            data={
+                "documents": [self.doc1.id, self.doc2.id, self.doc3.id],
+                "root_document_id": self.doc2.id,
+            },
+        )
+
+        self.assertTrue(serializer.is_valid(), serializer.errors)
+        self.assertEqual(
+            serializer.validated_data,
+            {
+                "documents": [self.doc1.id, self.doc2.id, self.doc3.id],
+                "root_document_id": self.doc2.id,
+            },
+        )
+
+    def test_requires_at_least_two_documents(self) -> None:
+        serializer = MergeDocumentsAsVersionsSerializer(
+            data={
+                "documents": [self.doc1.id],
+                "root_document_id": self.doc1.id,
+            },
+        )
+
+        self.assertFalse(serializer.is_valid())
+        self.assertEqual(
+            serializer.errors["non_field_errors"][0],
+            "At least two documents are required.",
+        )
+
+    def test_requires_root_document_to_be_selected(self) -> None:
+        serializer = MergeDocumentsAsVersionsSerializer(
+            data={
+                "documents": [self.doc1.id, self.doc2.id],
+                "root_document_id": self.doc3.id,
+            },
+        )
+
+        self.assertFalse(serializer.is_valid())
+        self.assertEqual(
+            serializer.errors["non_field_errors"][0],
+            "root_document_id must be one of the selected documents.",
+        )
+
+    def test_rejects_duplicate_documents(self) -> None:
+        serializer = MergeDocumentsAsVersionsSerializer(
+            data={
+                "documents": [self.doc1.id, self.doc1.id],
+                "root_document_id": self.doc1.id,
+            },
+        )
+
+        self.assertFalse(serializer.is_valid())
+        self.assertIn("documents", serializer.errors)