Convert test_rand to use pytest-style tests (#563)

Fix up the assert helpers, subclass form `object` rather than test case,
and use parametrization where appropriate.

One helper method on the original `TestCase` was the ability to create
temporary directories that were cleaned up at the end of the test --
now we use a pytest fixture instead: http://doc.pytest.org/en/latest/tmpdir.html

Addresses #340.

4 files changed, 98 insertions, 97 deletions

diff --git a/src/OpenSSL/rand.py b/src/OpenSSL/rand.py
index cce1327..a22f9e5 100644
--- a/src/OpenSSL/rand.py
+++ b/src/OpenSSL/rand.py
@@ -107,7 +107,7 @@ def status():
     """
     Check whether the PRNG has been seeded with enough data.
 
-    :return: :obj:`True` if the PRNG is seeded enough, :obj:`False` otherwise.
+    :return: 1 if the PRNG is seeded enough, 0 otherwise.
     """
     return _lib.RAND_status()
 
diff --git a/tests/conftest.py b/tests/conftest.py
index 5a9954f..366624e 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,6 +1,10 @@
 # Copyright (c) The pyOpenSSL developers
 # See LICENSE for details.
 
+from tempfile import mktemp
+
+import pytest
+
 
 def pytest_report_header(config):
     import OpenSSL.SSL
@@ -10,3 +14,13 @@ def pytest_report_header(config):
         openssl=OpenSSL.SSL.SSLeay_version(OpenSSL.SSL.SSLEAY_VERSION),
         cryptography=cryptography.__version__
     )
+
+
+@pytest.fixture
+def tmpfile(tmpdir):
+    """
+    Return UTF-8-encoded bytes of a path to a tmp file.
+
+    The file will be cleaned up after the test run.
+    """
+    return mktemp(dir=tmpdir.dirname).encode("utf-8")
diff --git a/tests/test_rand.py b/tests/test_rand.py
index 0350e9e..7574412 100644
--- a/tests/test_rand.py
+++ b/tests/test_rand.py
@@ -2,7 +2,7 @@
 # See LICENSE for details.
 
 """
-Unit tests for :py:obj:`OpenSSL.rand`.
+Unit tests for `OpenSSL.rand`.
 """
 
 import os
@@ -13,146 +13,133 @@ import pytest
 
 from OpenSSL import rand
 
-from .util import NON_ASCII, TestCase
+from .util import NON_ASCII
 
 
-class RandTests(TestCase):
-    def test_bytes_wrong_args(self):
+class TestRand(object):
+
+    @pytest.mark.parametrize('args', [
+        (None),
+        (b"foo"),
+    ])
+    def test_bytes_wrong_args(self, args):
         """
-        :py:obj:`OpenSSL.rand.bytes` raises :py:obj:`TypeError` if called with
-        the wrong number of arguments or with a non-:py:obj:`int` argument.
+        `OpenSSL.rand.bytes` raises `TypeError` if called with a non-`int`
+        argument.
         """
-        self.assertRaises(TypeError, rand.bytes)
-        self.assertRaises(TypeError, rand.bytes, None)
-        self.assertRaises(TypeError, rand.bytes, 3, None)
+        with pytest.raises(TypeError):
+            rand.bytes(*args)
 
-    def test_insufficientMemory(self):
+    def test_insufficient_memory(self):
         """
-        :py:obj:`OpenSSL.rand.bytes` raises :py:obj:`MemoryError` if more bytes
-        are requested than will fit in memory.
+        `OpenSSL.rand.bytes` raises `MemoryError` if more bytes are requested
+        than will fit in memory.
         """
-        self.assertRaises(MemoryError, rand.bytes, sys.maxsize)
+        with pytest.raises(MemoryError):
+            rand.bytes(sys.maxsize)
 
     def test_bytes(self):
         """
-        Verify that we can obtain bytes from rand_bytes() and
-        that they are different each time.  Test the parameter
-        of rand_bytes() for bad values.
+        Verify that we can obtain bytes from rand_bytes() and that they are
+        different each time.  Test the parameter of rand_bytes() for
+        bad values.
         """
         b1 = rand.bytes(50)
-        self.assertEqual(len(b1), 50)
+        assert len(b1) == 50
         b2 = rand.bytes(num_bytes=50)  # parameter by name
-        self.assertNotEqual(b1, b2)  # Hip, Hip, Horay! FIPS complaince
+        assert b1 != b2  # Hip, Hip, Horay! FIPS complaince
         b3 = rand.bytes(num_bytes=0)
-        self.assertEqual(len(b3), 0)
-        exc = self.assertRaises(ValueError, rand.bytes, -1)
-        self.assertEqual(str(exc), "num_bytes must not be negative")
+        assert len(b3) == 0
+        with pytest.raises(ValueError) as exc:
+            rand.bytes(-1)
+        assert str(exc.value) == "num_bytes must not be negative"
 
-    def test_add_wrong_args(self):
+    @pytest.mark.parametrize('args', [
+        (b"foo", None),
+        (None, 3),
+    ])
+    def test_add_wrong_args(self, args):
         """
-        When called with the wrong number of arguments, or with arguments not
-        of type :py:obj:`str` and :py:obj:`int`, :py:obj:`OpenSSL.rand.add`
-        raises :py:obj:`TypeError`.
+        `OpenSSL.rand.add` raises `TypeError` if called with arguments not of
+        type `str` and `int`.
         """
-        self.assertRaises(TypeError, rand.add)
-        self.assertRaises(TypeError, rand.add, b"foo", None)
-        self.assertRaises(TypeError, rand.add, None, 3)
-        self.assertRaises(TypeError, rand.add, b"foo", 3, None)
+        with pytest.raises(TypeError):
+            rand.add(*args)
 
     def test_add(self):
         """
-        :py:obj:`OpenSSL.rand.add` adds entropy to the PRNG.
+        `OpenSSL.rand.add` adds entropy to the PRNG.
         """
         rand.add(b'hamburger', 3)
 
-    def test_seed_wrong_args(self):
+    @pytest.mark.parametrize('args', [
+        (None),
+        (42),
+    ])
+    def test_seed_wrong_args(self, args):
         """
-        When called with the wrong number of arguments, or with
-        a non-:py:obj:`str` argument, :py:obj:`OpenSSL.rand.seed` raises
-        :py:obj:`TypeError`.
+        `OpenSSL.rand.seed` raises `TypeError` if called with
+        a non-`str` argument.
         """
-        self.assertRaises(TypeError, rand.seed)
-        self.assertRaises(TypeError, rand.seed, None)
-        self.assertRaises(TypeError, rand.seed, b"foo", None)
+        with pytest.raises(TypeError):
+            rand.seed(*args)
 
     def test_seed(self):
         """
-        :py:obj:`OpenSSL.rand.seed` adds entropy to the PRNG.
+        `OpenSSL.rand.seed` adds entropy to the PRNG.
         """
         rand.seed(b'milk shake')
 
-    def test_status_wrong_args(self):
-        """
-        :py:obj:`OpenSSL.rand.status` raises :py:obj:`TypeError` when called
-        with any arguments.
-        """
-        self.assertRaises(TypeError, rand.status, None)
-
     def test_status(self):
         """
-        :py:obj:`OpenSSL.rand.status` returns :py:obj:`True` if the PRNG has
-        sufficient entropy, :py:obj:`False` otherwise.
+        `OpenSSL.rand.status` returns `1` if the PRNG has sufficient entropy,
+        `0` otherwise.
         """
         # It's hard to know what it is actually going to return.  Different
         # OpenSSL random engines decide differently whether they have enough
         # entropy or not.
-        self.assertTrue(rand.status() in (1, 2))
+        assert rand.status() in (0, 1)
 
-    def test_egd_warning(self):
+    @pytest.mark.parametrize('args', [
+        (b"foo", 255),
+        (b"foo",),
+    ])
+    def test_egd_warning(self, args):
         """
         Calling egd raises :exc:`DeprecationWarning`.
         """
-        pytest.deprecated_call(rand.egd, b"foo", 255)
-        pytest.deprecated_call(rand.egd, b"foo")
-
-    def test_egd_wrong_args(self):
-        """
-        :meth:`OpenSSL.rand.egd` raises :exc:`TypeError` when called with the
-        wrong number of arguments or with arguments not of type :obj:`str` and
-        :obj:`int`.
-        """
-        for args in [(),
-                     (None,),
-                     ("foo", None),
-                     (None, 3),
-                     ("foo", 3, None)]:
-            with pytest.raises(TypeError):
-                rand.egd(*args)
-
-    def test_cleanup_wrong_args(self):
-        """
-        :py:obj:`OpenSSL.rand.cleanup` raises :py:obj:`TypeError` when called
-        with any arguments.
-        """
-        self.assertRaises(TypeError, rand.cleanup, None)
+        pytest.deprecated_call(rand.egd, *args)
 
     def test_cleanup(self):
         """
-        :py:obj:`OpenSSL.rand.cleanup` releases the memory used by the PRNG and
-        returns :py:obj:`None`.
+        `OpenSSL.rand.cleanup` releases the memory used by the PRNG and
+        returns `None`.
         """
-        self.assertIdentical(rand.cleanup(), None)
+        assert rand.cleanup() is None
 
-    def test_load_file_wrong_args(self):
+    @pytest.mark.parametrize('args', [
+        ("foo", None),
+        (None, 1),
+    ])
+    def test_load_file_wrong_args(self, args):
         """
-        :py:obj:`OpenSSL.rand.load_file` raises :py:obj:`TypeError` when called
-        the wrong number of arguments or arguments not of type :py:obj:`str`
-        and :py:obj:`int`.
+        `OpenSSL.rand.load_file` raises `TypeError` when with arguments
+        not of type `str` and `int`.
         """
-        self.assertRaises(TypeError, rand.load_file)
-        self.assertRaises(TypeError, rand.load_file, "foo", None)
-        self.assertRaises(TypeError, rand.load_file, None, 1)
-        self.assertRaises(TypeError, rand.load_file, "foo", 1, None)
+        with pytest.raises(TypeError):
+            rand.load_file(*args)
 
-    def test_write_file_wrong_args(self):
+    @pytest.mark.parametrize('args', [
+        None,
+        1,
+    ])
+    def test_write_file_wrong_args(self, args):
         """
-        :py:obj:`OpenSSL.rand.write_file` raises :py:obj:`TypeError` when
-        called with the wrong number of arguments or a non-:py:obj:`str`
-        argument.
+        `OpenSSL.rand.write_file` raises `TypeError` when called with
+        a non-`str` argument.
         """
-        self.assertRaises(TypeError, rand.write_file)
-        self.assertRaises(TypeError, rand.write_file, None)
-        self.assertRaises(TypeError, rand.write_file, "foo", None)
+        with pytest.raises(TypeError):
+            rand.write_file(*args)
 
     def _read_write_test(self, path):
         """
@@ -168,7 +155,7 @@ class RandTests(TestCase):
 
             # Verify length of written file
             size = os.stat(path)[stat.ST_SIZE]
-            self.assertEqual(1024, size)
+            assert size == 1024
 
             # Read random bytes from file
             rand.load_file(path)
@@ -177,19 +164,19 @@ class RandTests(TestCase):
             # Cleanup
             os.unlink(path)
 
-    def test_bytes_paths(self):
+    def test_bytes_paths(self, tmpfile):
         """
         Random data can be saved and loaded to files with paths specified as
         bytes.
         """
-        path = self.mktemp()
+        path = tmpfile
         path += NON_ASCII.encode(sys.getfilesystemencoding())
         self._read_write_test(path)
 
-    def test_unicode_paths(self):
+    def test_unicode_paths(self, tmpfile):
         """
         Random data can be saved and loaded to files with paths specified as
         unicode.
         """
-        path = self.mktemp().decode('utf-8') + NON_ASCII
+        path = tmpfile.decode('utf-8') + NON_ASCII
         self._read_write_test(path)
diff --git a/tox.ini b/tox.ini
index 8701977..9a41630 100644
--- a/tox.ini
+++ b/tox.ini
@@ -17,7 +17,7 @@ setenv =
     PIP_NO_BINARY=cryptography
 commands =
     openssl version
-    coverage run --parallel -m pytest {posargs}
+    coverage run --parallel -m pytest -v {posargs}
 
 [testenv:py27-twistedMaster]
 deps =