general: move most core tests inside my.core.tests package

- distributes tests alongside the package, might be convenient for package users
- removes some weird indirection (e.g. dummy test files improting tests from modules)
- makes the command line for tests cleaner (e.g. no need to remember to manually add files to tox.ini)
- tests automatically covered by mypy (so makes mypy runs cleaner and ultimately better coverage)

The (vague) convention is

- tests/somemodule.py -- testing my.core.somemodule, contains tests directly re
- tests/test_something.py -- testing a specific feature, e.g. test_get_files.py tests get_files methon only

my/core/tests/structure.py

@@ -0,0 +1,38 @@
+from pathlib import Path
+
+from ..structure import match_structure
+
+import pytest
+
+
+structure_data: Path = Path(__file__).parent / "structure_data"
+
+gdpr_expected = ("comments", "messages/index.csv", "profile")
+
+
+def test_gdpr_structure_exists() -> None:
+    with match_structure(structure_data, expected=gdpr_expected) as results:
+        assert results == (structure_data / "gdpr_subdirs" / "gdpr_export",)
+
+
+def test_gdpr_unzip() -> None:
+    with match_structure(structure_data / "gdpr_export.zip", expected=gdpr_expected) as results:
+        assert len(results) == 1
+        extracted = results[0]
+        index_file = extracted / "messages" / "index.csv"
+        assert index_file.read_text().strip() == "test message"
+
+    # make sure the temporary directory this created no longer exists
+    assert not extracted.exists()
+
+
+def test_match_partial() -> None:
+    # a partial match should match both the 'broken' and 'gdpr_export' directories
+    with match_structure(structure_data / "gdpr_subdirs", expected=gdpr_expected, partial=True) as results:
+        assert len(results) == 2
+
+
+def test_not_directory() -> None:
+    with pytest.raises(NotADirectoryError, match=r"Expected either a zipfile or a directory"):
+        with match_structure(structure_data / "messages/index.csv", expected=gdpr_expected):
+            pass