diff --git a/MANIFEST.in b/MANIFEST.in
index 72ef3c4..68eba37 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -5,5 +5,5 @@ include pyproject.toml
 recursive-include src *.pyx *.pyi py.typed
 include extern/bs.*
 include extern/bsplines.pxi
-include test.py
-recursive-include testdata *
+recursive-include tests *
+global-exclude __pycache__/* *.py[cod]
diff --git a/pyproject.toml b/pyproject.toml
index c634314..58c3fc3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -56,6 +56,9 @@ extinction = ["py.typed", "*.pyi"]
 [tool.setuptools.exclude-package-data]
 extinction = ["*.pyx", "*.c"]
 
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+
 [tool.cibuildwheel]
 test-requires = "pytest"
-test-command = "pytest {project}/test.py"
+test-command = "pytest {project}/tests"
diff --git a/test.py b/tests/test_extinction.py
similarity index 100%
rename from test.py
rename to tests/test_extinction.py
diff --git a/testdata/README.md b/tests/testdata/README.md
similarity index 100%
rename from testdata/README.md
rename to tests/testdata/README.md
diff --git a/testdata/fm_unred_2.3.dat b/tests/testdata/fm_unred_2.3.dat
similarity index 100%
rename from testdata/fm_unred_2.3.dat
rename to tests/testdata/fm_unred_2.3.dat
diff --git a/testdata/fm_unred_3.1.dat b/tests/testdata/fm_unred_3.1.dat
similarity index 100%
rename from testdata/fm_unred_3.1.dat
rename to tests/testdata/fm_unred_3.1.dat
diff --git a/testdata/fm_unred_4.0.dat b/tests/testdata/fm_unred_4.0.dat
similarity index 100%
rename from testdata/fm_unred_4.0.dat
rename to tests/testdata/fm_unred_4.0.dat
diff --git a/testdata/fm_unred_5.3.dat b/tests/testdata/fm_unred_5.3.dat
similarity index 100%
rename from testdata/fm_unred_5.3.dat
rename to tests/testdata/fm_unred_5.3.dat
diff --git a/testdata/run.pro b/tests/testdata/run.pro
similarity index 100%
rename from testdata/run.pro
rename to tests/testdata/run.pro
diff --git a/tox.ini b/tox.ini
index e855769..13bc7fc 100644
--- a/tox.ini
+++ b/tox.ini
@@ -6,4 +6,4 @@ isolated_build = true
 [testenv]
 passenv = HOME
 deps = pytest
-commands = pytest test.py
+commands = pytest tests