diff --git a/my/core/kompress.py b/my/core/kompress.py
index 8ee1cfa..1f00013 100644
--- a/my/core/kompress.py
+++ b/my/core/kompress.py
@@ -3,13 +3,13 @@ Various helpers for compression
 """
 from __future__ import annotations
 
-from functools import total_ordering
 from datetime import datetime
+from functools import total_ordering
+import io
 import pathlib
 from pathlib import Path
 import sys
 from typing import Union, IO, Sequence, Any, Iterator
-import io
 
 PathIsh = Union[Path, str]
 
diff --git a/my/core/tests/__init__.py b/my/core/tests/__init__.py
new file mode 100644
index 0000000..9d38c26
--- /dev/null
+++ b/my/core/tests/__init__.py
@@ -0,0 +1,3 @@
+# hmm, sadly pytest --import-mode importlib --pyargs my.core.tests doesn't work properly without __init__.py
+# although it works if you run either my.core or my.core.tests.sqlite (for example) directly
+# so if it gets in the way could get rid of this later?
diff --git a/tests/core/test_denylist.py b/my/core/tests/denylist.py
similarity index 98%
rename from tests/core/test_denylist.py
rename to my/core/tests/denylist.py
index 4e55a1f..cca757d 100644
--- a/tests/core/test_denylist.py
+++ b/my/core/tests/denylist.py
@@ -1,11 +1,10 @@
-import warnings
-
+from datetime import datetime
 import json
 from pathlib import Path
-from datetime import datetime
 from typing import NamedTuple, Iterator
+import warnings
 
-from my.core.denylist import DenyList
+from ..denylist import DenyList
 
 
 class IP(NamedTuple):
@@ -30,7 +29,6 @@ def data() -> Iterator[IP]:
 def test_denylist(tmp_path: Path) -> None:
     tf = (tmp_path / "denylist.json").absolute()
     with warnings.catch_warnings(record=True):
-
         # create empty denylist (though file does not have to exist for denylist to work)
         tf.write_text("[]")
 
diff --git a/tests/core/test_kompress.py b/my/core/tests/kompress.py
similarity index 91%
rename from tests/core/test_kompress.py
rename to my/core/tests/kompress.py
index 1f37c34..19c4e82 100644
--- a/tests/core/test_kompress.py
+++ b/my/core/tests/kompress.py
@@ -1,10 +1,9 @@
-from datetime import datetime
-import lzma
 from pathlib import Path
+import lzma
 import sys
 import zipfile
 
-from my.core.kompress import kopen, kexists, CPath
+from ..kompress import kopen, kexists, CPath, ZipPath
 
 import pytest
 
@@ -14,27 +13,31 @@ structure_data: Path = Path(__file__).parent / "structure_data"
 
 def test_kopen(tmp_path: Path) -> None:
     "Plaintext handled transparently"
+    # fmt: off
     assert kopen(tmp_path / 'file'   ).read() == 'just plaintext'
     assert kopen(tmp_path / 'file.xz').read() == 'compressed text'
+    # fmt: on
 
     "For zips behaviour is a bit different (not sure about all this, tbh...)"
     assert kopen(tmp_path / 'file.zip', 'path/in/archive').read() == 'data in zip'
 
 
-# TODO here?
 def test_kexists(tmp_path: Path) -> None:
     # TODO also test top level?
+    # fmt: off
     assert     kexists(str(tmp_path / 'file.zip'), 'path/in/archive')
     assert not kexists(str(tmp_path / 'file.zip'), 'path/notin/archive')
+    # fmt: on
 
     # TODO not sure about this?
     assert not kexists(tmp_path / 'nosuchzip.zip', 'path/in/archive')
 
 
 def test_cpath(tmp_path: Path) -> None:
+    # fmt: off
     CPath(str(tmp_path / 'file'  )).read_text() == 'just plaintext'
     CPath(    tmp_path / 'file.xz').read_text() == 'compressed text'
-    # TODO not sure about zip files??
+    # fmt: on
 
 
 @pytest.fixture(autouse=True)
@@ -51,12 +54,7 @@ def prepare(tmp_path: Path):
         pass
 
 
-@pytest.mark.skipif(
-    sys.version_info[:2] < (3, 8),
-    reason=f"ZipFile.Path is only available since 3.8",
-)
 def test_zippath() -> None:
-    from my.core.kompress import ZipPath
     target = structure_data / 'gdpr_export.zip'
     assert target.exists(), target  # precondition
 
@@ -87,6 +85,7 @@ def test_zippath() -> None:
 
     rpaths = [p.relative_to(zp) for p in matched]
     gdpr_export = Path('gdpr_export')
+    # fmt: off
     assert rpaths == [
         gdpr_export,
         gdpr_export / 'comments',
@@ -96,7 +95,7 @@ def test_zippath() -> None:
         gdpr_export / 'messages',
         gdpr_export / 'messages' / 'index.csv',
     ], rpaths
-
+    # fmt: on
 
     # TODO hmm this doesn't work atm, whereas Path does
     # not sure if it should be defensive or something...
@@ -107,10 +106,12 @@ def test_zippath() -> None:
     assert (ZipPath(target) / 'gdpr_export' / 'comments').exists()
 
     jsons = [p.relative_to(zp / 'gdpr_export') for p in zp.rglob('*.json')]
+    # fmt: off
     assert jsons == [
-        Path('comments','comments.json'),
-        Path('profile','settings.json'),
+        Path('comments', 'comments.json'),
+        Path('profile' , 'settings.json'),
     ]
+    # fmt: on
 
     # NOTE: hmm interesting, seems that ZipPath is happy with forward slash regardless OS?
     assert list(zp.rglob('mes*')) == [ZipPath(target, 'gdpr_export/messages')]
diff --git a/tests/sqlite.py b/my/core/tests/sqlite.py
similarity index 91%
rename from tests/sqlite.py
rename to my/core/tests/sqlite.py
index f80636e..b3ecffe 100644
--- a/tests/sqlite.py
+++ b/my/core/tests/sqlite.py
@@ -1,10 +1,10 @@
+from concurrent.futures import ProcessPoolExecutor
 from pathlib import Path
 import shutil
 import sqlite3
 from tempfile import TemporaryDirectory
 
-
-from my.core.sqlite import sqlite_connect_immutable, sqlite_copy_and_open
+from ..sqlite import sqlite_connect_immutable, sqlite_copy_and_open
 
 
 def test_sqlite_read_with_wal(tmp_path: Path) -> None:
@@ -27,13 +27,14 @@ def test_sqlite_read_with_wal(tmp_path: Path) -> None:
         assert len(wals) == 1
 
         ## now run the tests in separate process to ensure there is no potential for reusing sqlite connections or something
-        from concurrent.futures import ProcessPoolExecutor as Pool
-        with Pool(1) as pool:
+        with ProcessPoolExecutor(1) as pool:
             # merely using it for ctx manager..
+            # fmt: off
             pool.submit(_test_do_copy         , db).result()
             pool.submit(_test_do_immutable    , db).result()
             pool.submit(_test_do_copy_and_open, db).result()
             pool.submit(_test_open_asis       , db).result()
+            # fmt: on
 
 
 def _test_do_copy(db: Path) -> None:
diff --git a/tests/core/test_structure.py b/my/core/tests/structure.py
similarity index 71%
rename from tests/core/test_structure.py
rename to my/core/tests/structure.py
index 1ad46fe..beb8e7f 100644
--- a/tests/core/test_structure.py
+++ b/my/core/tests/structure.py
@@ -1,8 +1,8 @@
-import pytest
-
 from pathlib import Path
 
-from my.core.structure import match_structure
+from ..structure import match_structure
+
+import pytest
 
 
 structure_data: Path = Path(__file__).parent / "structure_data"
@@ -16,10 +16,7 @@ def test_gdpr_structure_exists() -> None:
 
 
 def test_gdpr_unzip() -> None:
-
-    with match_structure(
-        structure_data / "gdpr_export.zip", expected=gdpr_expected
-    ) as results:
+    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"
@@ -31,15 +28,11 @@ def test_gdpr_unzip() -> None:
 
 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:
+    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
-        ):
+        with match_structure(structure_data / "messages/index.csv", expected=gdpr_expected):
             pass
diff --git a/tests/core/structure_data/gdpr_export.zip b/my/core/tests/structure_data/gdpr_export.zip
similarity index 100%
rename from tests/core/structure_data/gdpr_export.zip
rename to my/core/tests/structure_data/gdpr_export.zip
diff --git a/tests/core/structure_data/gdpr_subdirs/broken_export/comments/comments.json b/my/core/tests/structure_data/gdpr_subdirs/broken_export/comments/comments.json
similarity index 100%
rename from tests/core/structure_data/gdpr_subdirs/broken_export/comments/comments.json
rename to my/core/tests/structure_data/gdpr_subdirs/broken_export/comments/comments.json
diff --git a/tests/core/structure_data/gdpr_subdirs/broken_export/messages/index.csv b/my/core/tests/structure_data/gdpr_subdirs/broken_export/messages/index.csv
similarity index 100%
rename from tests/core/structure_data/gdpr_subdirs/broken_export/messages/index.csv
rename to my/core/tests/structure_data/gdpr_subdirs/broken_export/messages/index.csv
diff --git a/tests/core/structure_data/gdpr_subdirs/gdpr_export/comments/comments.json b/my/core/tests/structure_data/gdpr_subdirs/gdpr_export/comments/comments.json
similarity index 100%
rename from tests/core/structure_data/gdpr_subdirs/gdpr_export/comments/comments.json
rename to my/core/tests/structure_data/gdpr_subdirs/gdpr_export/comments/comments.json
diff --git a/tests/core/structure_data/gdpr_subdirs/gdpr_export/messages/index.csv b/my/core/tests/structure_data/gdpr_subdirs/gdpr_export/messages/index.csv
similarity index 100%
rename from tests/core/structure_data/gdpr_subdirs/gdpr_export/messages/index.csv
rename to my/core/tests/structure_data/gdpr_subdirs/gdpr_export/messages/index.csv
diff --git a/tests/core/structure_data/gdpr_subdirs/gdpr_export/profile/settings.json b/my/core/tests/structure_data/gdpr_subdirs/gdpr_export/profile/settings.json
similarity index 100%
rename from tests/core/structure_data/gdpr_subdirs/gdpr_export/profile/settings.json
rename to my/core/tests/structure_data/gdpr_subdirs/gdpr_export/profile/settings.json
diff --git a/tests/cli.py b/my/core/tests/test_cli.py
similarity index 85%
rename from tests/cli.py
rename to my/core/tests/test_cli.py
index fce53b7..4d847ae 100644
--- a/tests/cli.py
+++ b/my/core/tests/test_cli.py
@@ -1,5 +1,7 @@
 import os
 from subprocess import check_call
+import sys
+
 
 def test_lists_modules() -> None:
     # hack PYTHONUTF8 for windows
@@ -11,4 +13,4 @@ def test_lists_modules() -> None:
         **os.environ,
         'PYTHONUTF8': '1',
     }
-    check_call(['hpi', 'modules'], env=env)
+    check_call([sys.executable, '-m', 'my.core', 'modules'], env=env)
diff --git a/tests/get_files.py b/my/core/tests/test_get_files.py
similarity index 85%
rename from tests/get_files.py
rename to my/core/tests/test_get_files.py
index daeef71..fdec5c0 100644
--- a/tests/get_files.py
+++ b/my/core/tests/test_get_files.py
@@ -1,30 +1,33 @@
 import os
 from pathlib import Path
+import shutil
+import tempfile
 from typing import TYPE_CHECKING
 
-from my.core.compat import windows
-from my.core.common import get_files
+from ..compat import windows
+from ..common import get_files
 
 import pytest
 
 
- # hack to replace all /tmp with 'real' tmp dir
- # not ideal, but makes tests more concise
+# hack to replace all /tmp with 'real' tmp dir
+# not ideal, but makes tests more concise
 def _get_files(x, *args, **kwargs):
-    import my.core.common as C
+    from ..common import get_files as get_files_orig
+
     def repl(x):
         if isinstance(x, str):
             return x.replace('/tmp', TMP)
         elif isinstance(x, Path):
-            assert x.parts[:2] == (os.sep, 'tmp') # meh
+            assert x.parts[:2] == (os.sep, 'tmp')  # meh
             return Path(TMP) / Path(*x.parts[2:])
         else:
             # iterable?
             return [repl(i) for i in x]
 
     x = repl(x)
-    res = C.get_files(x, *args, **kwargs)
-    return tuple(Path(str(i).replace(TMP, '/tmp')) for i in res) # hack back for asserts..
+    res = get_files_orig(x, *args, **kwargs)
+    return tuple(Path(str(i).replace(TMP, '/tmp')) for i in res)  # hack back for asserts..
 
 
 if not TYPE_CHECKING:
@@ -40,7 +43,6 @@ def test_single_file() -> None:
     with pytest.raises(Exception):
         get_files('/tmp/hpi_test/file.ext')
 
-
     create('/tmp/hpi_test/file.ext')
 
     '''
@@ -48,16 +50,11 @@ def test_single_file() -> None:
     1. Return type is a tuple, it's friendlier for hashing/caching
     2. It always return pathlib.Path instead of plain strings
     '''
-    assert get_files('/tmp/hpi_test/file.ext') == (
-        Path('/tmp/hpi_test/file.ext'),
-    )
-
+    assert get_files('/tmp/hpi_test/file.ext') == (Path('/tmp/hpi_test/file.ext'),)
 
     "if the path starts with ~, we expand it"
-    if not windows: # windows dowsn't have bashrc.. ugh
-        assert get_files('~/.bashrc') == (
-            Path('~').expanduser() / '.bashrc',
-        )
+    if not windows:  # windows doesn't have bashrc.. ugh
+        assert get_files('~/.bashrc') == (Path('~').expanduser() / '.bashrc',)
 
 
 def test_multiple_files() -> None:
@@ -74,6 +71,7 @@ def test_multiple_files() -> None:
     create('/tmp/hpi_test/dir3/')
     create('/tmp/hpi_test/dir3/ttt')
 
+    # fmt: off
     assert get_files([
         Path('/tmp/hpi_test/dir3'), # it takes in Path as well as str
         '/tmp/hpi_test/dir1',
@@ -83,6 +81,7 @@ def test_multiple_files() -> None:
         Path('/tmp/hpi_test/dir1/zzz'),
         Path('/tmp/hpi_test/dir3/ttt'),
     )
+    # fmt: on
 
 
 def test_explicit_glob() -> None:
@@ -130,27 +129,26 @@ def test_no_files() -> None:
     '''
     Test for empty matches. They work, but should result in warning
     '''
-    assert get_files('')         == ()
+    assert get_files('') == ()
 
     # todo test these for warnings?
-    assert get_files([])         == ()
+    assert get_files([]) == ()
     assert get_files('bad*glob') == ()
 
 
 # TODO not sure if should uniquify if the filenames end up same?
 # TODO not sure about the symlinks? and hidden files?
 
-import tempfile
 TMP = tempfile.gettempdir()
 test_path = Path(TMP) / 'hpi_test'
 
+
 def setup():
     teardown()
     test_path.mkdir()
 
 
 def teardown():
-    import shutil
     if test_path.is_dir():
         shutil.rmtree(test_path)
 
diff --git a/tests/test_tmp_config.py b/my/core/tests/test_tmp_config.py
similarity index 88%
rename from tests/test_tmp_config.py
rename to my/core/tests/test_tmp_config.py
index b22f9cf..e5a24cc 100644
--- a/tests/test_tmp_config.py
+++ b/my/core/tests/test_tmp_config.py
@@ -1,15 +1,12 @@
-from pathlib import Path
-import tempfile
-
-from my.core.cfg import tmp_config
-
-import pytest
+from ..cfg import tmp_config
 
 
 def _init_default_config() -> None:
     import my.config
+
     class default_config:
         count = 5
+
     my.config.simple = default_config  # type: ignore[assignment,misc]
 
 
@@ -19,7 +16,6 @@ def test_tmp_config() -> None:
     ## later would be nice to be a bit more careful about them
     _init_default_config()
     from my.simple import items
-    ##
 
     assert len(list(items())) == 5
 
diff --git a/tests/core.py b/tests/core.py
deleted file mode 100644
index 339f786..0000000
--- a/tests/core.py
+++ /dev/null
@@ -1,25 +0,0 @@
-'''
-NOTE: Sigh. it's nice to be able to define the tests next to the source code (so it serves as documentation).
-However, if you run 'pytest --pyargs my.core', it detects 'core' package name (because there is no my/__init__.py)
-(see https://docs.pytest.org/en/latest/goodpractices.html#tests-as-part-of-application-code)
-
-This results in relative imports failing (e.g. from ..core import...).
-
-By using this helper file, pytest can detect the package name properly. A bit meh, but perhaps later,
-we can run against the tests in my.core directly.
-
-'''
-
-from my.core.cfg            import *
-from my.core.common         import *
-from my.core.core_config    import *
-from my.core.error          import *
-from my.core.util           import *
-from my.core.discovery_pure import *
-from my.core.freezer        import *
-from my.core.stats          import *
-from my.core.query          import *
-from my.core.query_range    import *
-from my.core.serialize      import test_serialize_fallback
-from my.core.sqlite         import *
-from my.core.__main__       import *
diff --git a/tests/core/test_pandas.py b/tests/core/test_pandas.py
deleted file mode 100644
index bedab26..0000000
--- a/tests/core/test_pandas.py
+++ /dev/null
@@ -1 +0,0 @@
-from my.core.pandas import *
diff --git a/tox.ini b/tox.ini
index 2809e3c..3124618 100644
--- a/tox.ini
+++ b/tox.ini
@@ -19,12 +19,26 @@ passenv =
 [testenv:tests-core]
 commands =
     pip install -e .[testing]
+    
+    # seems that denylist tests rely on it? ideally we should get rid of this in tests-core
+    pip install orjson
+
     {envpython} -m pytest \
-                      tests/core.py            \
-                      tests/sqlite.py          \
-                      tests/get_files.py       \
-                      tests/test_tmp_config.py \
-                      {posargs}
+        # importlib is the new suggested import-mode
+        # without it test package names end up as core.tests.* instead of my.core.tests.*
+        --import-mode=importlib     \
+        --pyargs my.core            \
+        # ignore orgmode because it imports orgparse
+        # tbh not sure if it even belongs to core, maybe move somewhere else..
+        # same with pandas?
+        --ignore my/core/orgmode.py \
+        # causes error during test collection on 3.8
+        # dataset is deprecated anyway so whatever
+        --ignore my/core/dataset.py \
+        # this test uses orjson which is an optional dependency
+        # it would be covered by tests-all
+        -k 'not test_nt_serialize' \
+        {posargs}
 
 
 # todo maybe also have core tests and misc tests? since ideally want them without dependencies
@@ -94,11 +108,6 @@ commands =
                     {posargs}
     cat .coverage.mypy-core/index.txt
 
-    # todo hmm might be better to move modules test in a separate subpackage?
-    {envpython} -m mypy --install-types --non-interactive \
-                    tests \
-                    --exclude 'tests/(bluemaestro|emfit|takeout|pdfs|jawbone).py'
-
 
 # specific modules that are known to be mypy compliant (to avoid false negatives)
 # todo maybe split into separate jobs? need to add comment how to run