First test for jupytext + black #154

requirements-dev.txt

@@ -1,4 +1,5 @@
 flake8
+black
 pytest
 pytest-cov==2.5.1
 codecov

tests/test_black.py

@@ -0,0 +1,46 @@
+import pytest
+from shutil import copyfile
+from testfixtures import compare
+from .utils import list_notebooks
+from jupytext import readf
+from jupytext.cli import system, jupytext
+
+
+def black_version():
+    try:
+        return system('black', ['--version'])
+    except FileNotFoundError:  # pragma: no cover
+        return None
+
+
+requires_black = pytest.mark.skipif(not black_version(), reason='black not found')
+
+
+def remove_spaces_and_commas(text, chars=[' ', '\n', ',', "'", '"']):
+    for char in chars:
+        text = text.replace(char, '')
+    return text
+
+
+@requires_black
+@pytest.mark.parametrize('nb_file', list_notebooks('ipynb_py'))
+def test_apply_black_on_python_notebooks(nb_file, tmpdir):
+    tmp_ipynb = str(tmpdir.join('notebook.ipynb'))
+    tmp_py = str(tmpdir.join('notebook.py'))
+    copyfile(nb_file, tmp_ipynb)
+
+    jupytext(args=[tmp_ipynb, '--to', 'py:percent'])
+    system('black', tmp_py)
+    jupytext(args=[tmp_py, '--to', 'ipynb', '--update'])
+
+    nb1 = readf(nb_file)
+    nb2 = readf(tmp_ipynb)
+
+    assert len(nb1.cells) == len(nb2.cells)
+    for c1, c2 in zip(nb1.cells, nb2.cells):
+        # same content (almost)
+        assert remove_spaces_and_commas(c1.source) == remove_spaces_and_commas(c2.source)
+        # python representation is pep8
+        assert 'lines_to_next_cell' not in c2.metadata
+
+    compare(nb1.metadata, nb2.metadata)