Probably a good test for the migration

src/documents/tests/test_migration_sha256_checksums.py

@@ -0,0 +1,119 @@
+import hashlib
+import shutil
+import tempfile
+from pathlib import Path
+
+from django.conf import settings
+from django.test import override_settings
+
+from documents.tests.utils import TestMigrations
+
+
+def _sha256(data: bytes) -> str:
+    return hashlib.sha256(data).hexdigest()
+
+
+class TestSha256ChecksumDataMigration(TestMigrations):
+    """recompute_checksums correctly updates document checksums from MD5 to SHA256."""
+
+    migrate_from = "0015_document_version_index_and_more"
+    migrate_to = "0016_sha256_checksums"
+
+    ORIGINAL_CONTENT = b"original file content for sha256 migration test"
+    ARCHIVE_CONTENT = b"archive file content for sha256 migration test"
+
+    def setUpBeforeMigration(self, apps) -> None:
+        self._originals_dir = Path(tempfile.mkdtemp())
+        self._archive_dir = Path(tempfile.mkdtemp())
+        self._settings_override = override_settings(
+            ORIGINALS_DIR=self._originals_dir,
+            ARCHIVE_DIR=self._archive_dir,
+        )
+        self._settings_override.enable()
+        Document = apps.get_model("documents", "Document")
+
+        # doc1: original file present, no archive
+        (settings.ORIGINALS_DIR / "doc1.txt").write_bytes(self.ORIGINAL_CONTENT)
+        self.doc1_id = Document.objects.create(
+            title="Doc 1",
+            mime_type="text/plain",
+            filename="doc1.txt",
+            checksum="a" * 32,
+        ).pk
+
+        # doc2: original and archive both present
+        (settings.ORIGINALS_DIR / "doc2.txt").write_bytes(self.ORIGINAL_CONTENT)
+        (settings.ARCHIVE_DIR / "doc2.pdf").write_bytes(self.ARCHIVE_CONTENT)
+        self.doc2_id = Document.objects.create(
+            title="Doc 2",
+            mime_type="text/plain",
+            filename="doc2.txt",
+            checksum="b" * 32,
+            archive_filename="doc2.pdf",
+            archive_checksum="c" * 32,
+        ).pk
+
+        # doc3: original file missing — checksum must stay unchanged
+        self.doc3_id = Document.objects.create(
+            title="Doc 3",
+            mime_type="text/plain",
+            filename="missing_original.txt",
+            checksum="d" * 32,
+        ).pk
+
+        # doc4: original present, archive_filename set but archive file missing
+        (settings.ORIGINALS_DIR / "doc4.txt").write_bytes(self.ORIGINAL_CONTENT)
+        self.doc4_id = Document.objects.create(
+            title="Doc 4",
+            mime_type="text/plain",
+            filename="doc4.txt",
+            checksum="e" * 32,
+            archive_filename="missing_archive.pdf",
+            archive_checksum="f" * 32,
+        ).pk
+
+        # doc5: original present, archive_filename is None — archive_checksum must stay null
+        (settings.ORIGINALS_DIR / "doc5.txt").write_bytes(self.ORIGINAL_CONTENT)
+        self.doc5_id = Document.objects.create(
+            title="Doc 5",
+            mime_type="text/plain",
+            filename="doc5.txt",
+            checksum="0" * 32,
+            archive_filename=None,
+            archive_checksum=None,
+        ).pk
+
+    def tearDown(self) -> None:
+        super().tearDown()
+        self._settings_override.disable()
+        shutil.rmtree(self._originals_dir, ignore_errors=True)
+        shutil.rmtree(self._archive_dir, ignore_errors=True)
+
+    def test_original_checksum_updated_to_sha256_when_file_exists(self) -> None:
+        Document = self.apps.get_model("documents", "Document")
+        doc = Document.objects.get(pk=self.doc1_id)
+        self.assertEqual(doc.checksum, _sha256(self.ORIGINAL_CONTENT))
+
+    def test_both_checksums_updated_when_original_and_archive_exist(self) -> None:
+        Document = self.apps.get_model("documents", "Document")
+        doc = Document.objects.get(pk=self.doc2_id)
+        self.assertEqual(doc.checksum, _sha256(self.ORIGINAL_CONTENT))
+        self.assertEqual(doc.archive_checksum, _sha256(self.ARCHIVE_CONTENT))
+
+    def test_checksum_unchanged_when_original_file_missing(self) -> None:
+        Document = self.apps.get_model("documents", "Document")
+        doc = Document.objects.get(pk=self.doc3_id)
+        self.assertEqual(doc.checksum, "d" * 32)
+
+    def test_archive_checksum_unchanged_when_archive_file_missing(self) -> None:
+        Document = self.apps.get_model("documents", "Document")
+        doc = Document.objects.get(pk=self.doc4_id)
+        # Original was updated (file exists)
+        self.assertEqual(doc.checksum, _sha256(self.ORIGINAL_CONTENT))
+        # Archive was not updated (file missing)
+        self.assertEqual(doc.archive_checksum, "f" * 32)
+
+    def test_archive_checksum_stays_null_when_no_archive_filename(self) -> None:
+        Document = self.apps.get_model("documents", "Document")
+        doc = Document.objects.get(pk=self.doc5_id)
+        self.assertIsNone(doc.archive_checksum)