test_{samples,calculator}.py: migrate from nose to pytest.

nose is an obsoleted testing framework for Python, dead and
unmaintained since 2015.

Properly teardown fixtures after the tests.

Reference: https://bugs.debian.org/1018659
Reference: https://bugs.gentoo.org/878727
Closes: uvemas#114

tests/test_calculator.py

@@ -0,0 +1,15 @@
+import vitables.calculator.calculator as vtc
+
+
+class TestCalculator:
+    """Test calculator functionality."""
+
+    def test_extract_identifiers(self):
+        """Test function that extract marked identifiers from an expression."""
+        empty_set = vtc.extract_identifiers('')
+        assert len(empty_set) == 0
+        assert set(['$data']) == vtc.extract_identifiers('$data')
+        assert set(['$data']) == vtc.extract_identifiers('+$data*')
+        assert set(['$data']) == vtc.extract_identifiers('+$data*$data')
+        assert set(['$data', '$data1']) == vtc.extract_identifiers('+$data*$data1 + test')
+        assert set(['$data', '$test.data1']) == vtc.extract_identifiers('+$data*$test.data1 + test')

vitables/test/test_samples.py → tests/test_samples.py

@@ -1,10 +1,5 @@
 import sys
 import os.path
-import nose.tools as nt
-
-import sip
-sip.setapi('QString', 2)
-sip.setapi('QVariant', 2)
 
 from qtpy import QtWidgets
 from qtpy import QtCore
@@ -40,7 +35,7 @@ def assert_path(test, path):
     if not path:
         return
     index = get_index(test.model, path[0])
-    nt.assert_false(index is None)
+    assert index is not None
     test.view.activateNode(index)
     assert_path(test, path[1:])
 
@@ -182,11 +177,16 @@ def setup_class(cls):
         cls.model = cls.vtgui.dbs_tree_model
         cls.view = cls.vtgui.dbs_tree_view
 
+    @classmethod
+    def teardown_class(cls):
+        del cls.vtapp
+        del cls.app
+
     def test_opening_files(self):
         """Generate tests for given data files."""
         for filepath, nodes in self.TEST_NODES.items():
             for node in nodes:
-                yield self.check_node_open, filepath, node
+                self.check_node_open(filepath, node)
 
     def check_node_open(self, filepath, nodepath):
         """Open file get access to a node and read all cells."""