TEST: Create fresh in-memory database for each dft unit test

Author: effigies

nibabel/tests/test_dft.py

@@ -29,12 +29,21 @@ def setUpModule():
         raise unittest.SkipTest('Need pydicom for dft tests, skipping')
 
 
-def test_init():
+@pytest.fixture
+def db(monkeypatch):
+    """Build a dft database in memory to avoid cross-process races
+    and not modify the host filesystem."""
+    database = dft._DB(fname=":memory:")
+    monkeypatch.setattr(dft, "DB", database)
+    yield database
+
+
+def test_init(db):
     dft.clear_cache()
     dft.update_cache(data_dir)
 
 
-def test_study():
+def test_study(db):
     studies = dft.get_studies(data_dir)
     assert len(studies) == 1
     assert (studies[0].uid ==
@@ -48,7 +57,7 @@ def test_study():
     assert studies[0].patient_sex == 'F'
 
 
-def test_series():
+def test_series(db):
     studies = dft.get_studies(data_dir)
     assert len(studies[0].series) == 1
     ser = studies[0].series[0]
@@ -62,7 +71,7 @@ def test_series():
     assert ser.bits_stored == 12
 
 
-def test_storage_instances():
+def test_storage_instances(db):
     studies = dft.get_studies(data_dir)
     sis = studies[0].series[0].storage_instances
     assert len(sis) == 2
@@ -74,19 +83,19 @@ def test_storage_instances():
                  '1.3.12.2.1107.5.2.32.35119.2010011420300180088599504.1')
 
 
-def test_storage_instance():
+def test_storage_instance(db):
     pass
 
 
 @unittest.skipUnless(have_pil, 'could not import PIL.Image')
-def test_png():
+def test_png(db):
     studies = dft.get_studies(data_dir)
     data = studies[0].series[0].as_png()
     im = PImage.open(BytesIO(data))
     assert im.size == (256, 256)
 
 
-def test_nifti():
+def test_nifti(db):
     studies = dft.get_studies(data_dir)
     data = studies[0].series[0].as_nifti()
     assert len(data) == 352 + 2 * 256 * 256 * 2