Add tests for BaseFormatter

tests/unit/test_base_formatter.py

@@ -0,0 +1,103 @@
+"""Tests for the BaseFormatter object."""
+import optparse
+
+import mock
+import pytest
+
+from flake8.formatting import base
+from flake8 import style_guide
+
+
+def options(**kwargs):
+    """Create an optparse.Values instance."""
+    kwargs.setdefault('output_file', None)
+    return optparse.Values(kwargs)
+
+
+@pytest.mark.parametrize('filename', [None, 'out.txt'])
+def test_start(filename):
+    """Verify we open a new file in the start method."""
+    mock_open = mock.mock_open()
+    formatter = base.BaseFormatter(options(output_file=filename))
+    with mock.patch('flake8.formatting.base.open', mock_open):
+        formatter.start()
+
+    if filename is None:
+        assert mock_open.called is False
+    else:
+        mock_open.assert_called_once_with(filename, 'w')
+
+
+def test_stop():
+    """Verify we close open file objects."""
+    filemock = mock.Mock()
+    formatter = base.BaseFormatter(options())
+    formatter.output_fd = filemock
+    formatter.stop()
+
+    filemock.close.assert_called_once_with()
+    assert formatter.output_fd is None
+
+
+def test_format_needs_to_be_implemented():
+    """Ensure BaseFormatter#format raises a NotImplementedError."""
+    formatter = base.BaseFormatter(options())
+    with pytest.raises(NotImplementedError):
+        formatter.format('foo')
+
+
+def test_show_source_returns_nothing_when_not_showing_source():
+    """Ensure we return nothing when users want nothing."""
+    formatter = base.BaseFormatter(options(show_source=False))
+    assert formatter.show_source(
+        style_guide.Error('A000', 'file.py', 1, 1, 'error text', 'line')
+    ) is None
+
+
+@pytest.mark.parametrize('line, column', [
+    ('x=1\n', 2),
+    ('    x=(1\n       +2)\n', 5),
+    # TODO(sigmavirus24): Add more examples
+])
+def test_show_source_updates_physical_line_appropriately(line, column):
+    """Ensure the error column is appropriately indicated."""
+    formatter = base.BaseFormatter(options(show_source=True))
+    error = style_guide.Error('A000', 'file.py', 1, column, 'error', line)
+    output = formatter.show_source(error)
+    _, pointer = output.rsplit('\n', 1)
+    assert pointer.count(' ') == column
+
+
+def test_write_uses_an_output_file():
+    """Verify that we use the output file when it's present."""
+    line = 'Something to write'
+    source = 'source'
+    filemock = mock.Mock()
+
+    formatter = base.BaseFormatter(options())
+    formatter.output_fd = filemock
+    formatter.write(line, source)
+
+    assert filemock.write.called is True
+    assert filemock.write.call_count == 2
+    assert filemock.write.mock_calls == [
+        mock.call(line + formatter.newline),
+        mock.call(source + formatter.newline),
+    ]
+
+
+@mock.patch('flake8.formatting.base.print')
+def test_write_uses_print(print_function):
+    """Verify that we use the print function without an output file."""
+    line = 'Something to write'
+    source = 'source'
+
+    formatter = base.BaseFormatter(options())
+    formatter.write(line, source)
+
+    assert print_function.called is True
+    assert print_function.call_count == 2
+    assert print_function.mock_calls == [
+        mock.call(line),
+        mock.call(source),
+    ]