Add tests for get_grid, mocking GridStrategy

Rather than attempting to actually plot these grids and match against an
image or an SVG, we can instead mock out GridStrategy and ensure that
the correct arrangement of grids is returned.

Author: pganssle

tests/test_grids.py

@@ -0,0 +1,77 @@
+import pytest
+from unittest import mock
+
+from grid_strategy.strategies import SquareStrategy
+
+
+class SpecValue:
+    def __init__(self, rows, cols, parent=None):
+        self.rows = rows
+        self.cols = cols
+        self.parent = parent
+
+    def __repr__(self):
+        return f"{self.__class__.__name__}({self.rows}, {self.cols})"
+
+    def __eq__(self, other):
+        return self.rows == other.rows and self.cols == other.cols
+
+
+class GridSpecMock:
+    def __init__(self, nrows, ncols, *args, **kwargs):
+        self._nrows_ = nrows
+        self._ncols_ = ncols
+
+        self._args_ = args
+        self._kwargs_ = kwargs
+
+    def __getitem__(self, key_tup):
+        return SpecValue(*key_tup, self)
+
+
+@pytest.fixture
+def gridspec_mock():
+    class Figure:
+        pass
+
+    def figure(*args, **kwargs):
+        return Figure()
+
+    with mock.patch(f"grid_strategy._abc.gridspec.GridSpec", new=GridSpecMock) as g:
+        with mock.patch(f"grid_strategy._abc.plt.figure", new=figure):
+            yield g
+
+
+@pytest.mark.parametrize(
+    "align, n, exp_specs",
+    [
+        ("center", 1, [(0, slice(0, 1))]),
+        ("center", 2, [(0, slice(0, 1)), (0, slice(1, 2))]),
+        ("center", 3, [(0, slice(0, 2)), (0, slice(2, 4)), (1, slice(1, 3))]),
+        ("left", 3, [(0, slice(0, 2)), (0, slice(2, 4)), (1, slice(0, 2))]),
+        ("right", 3, [(0, slice(0, 2)), (0, slice(2, 4)), (1, slice(2, 4))]),
+        ("justified", 3, [(0, slice(0, 1)), (0, slice(1, 2)), (1, slice(0, 2))]),
+        (
+            "center",
+            8,
+            [
+                (0, slice(0, 2)),
+                (0, slice(2, 4)),
+                (0, slice(4, 6)),
+                (1, slice(1, 3)),
+                (1, slice(3, 5)),
+                (2, slice(0, 2)),
+                (2, slice(2, 4)),
+                (2, slice(4, 6)),
+            ],
+        ),
+        ("left", 2, [(0, slice(0, 1)), (0, slice(1, 2))]),
+    ],
+)
+def test_square_spec(gridspec_mock, align, n, exp_specs):
+    ss = SquareStrategy(align)
+
+    act = ss.get_grid(n)
+    exp = [SpecValue(*spec) for spec in exp_specs]
+
+    assert act == exp