Add a more robust testing framework

Try:
  `pytest` in the repo root
  `python setup.py test` in the repo root runs pytest
  `tox` in the repo root runs pytest in a virtualenv against all
        intalled interpreters
  `tox -e coverage` in the repo root produces a test coverage report

setup.cfg

@@ -1,2 +1,5 @@
+[aliases]
+test=pytest
+
 [wheel]
 universal = 1

setup.py

@@ -27,8 +27,12 @@ setup(
         'Programming Language :: Python :: 3',
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
-        'Programming Language :: Python :: 3.6'
+        'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7'
     ],
     packages=['sigmf'],
+    install_requires=['six', 'numpy'],
+    setup_requires=['pytest-runner'],
+    tests_require=['pytest>3'],
     zip_safe=False
 )

tests/conftest.py

@@ -0,0 +1,45 @@
+# Copyright 2017 GNU Radio Foundation
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+import tempfile
+
+import pytest
+
+from sigmf.sigmffile import SigMFFile
+
+from .testdata import TEST_FLOAT32_DATA, TEST_METADATA
+
+
+@pytest.yield_fixture
+def test_data_file():
+    with tempfile.NamedTemporaryFile() as t:
+        TEST_FLOAT32_DATA.tofile(t.name)
+        yield t
+
+
+@pytest.fixture
+def test_sigmffile(test_data_file):
+    f = SigMFFile()
+    f.set_global_field("core:datatype", "f32")
+    f.add_annotation(start_index=0, length=len(TEST_FLOAT32_DATA))
+    f.add_capture(start_index=0)
+    f.set_data_file(test_data_file.name)
+    assert f._metadata == TEST_METADATA
+    return f

tox.ini

@@ -0,0 +1,17 @@
+[tox]
+skip_missing_interpreters = True
+envlist = py27, py34, py35, py36, py37
+
+[testenv]
+usedevelop = True
+deps =
+    pytest
+    flake8
+commands =
+    pytest
+    - flake8
+
+[testenv:coverage]
+deps =
+    pytest-cov
+commands = py.test --cov-report term-missing --cov=sigmf tests