diff --git a/pytest.ini b/pytest.ini
new file mode 100644
index 0000000..3b4c488
--- /dev/null
+++ b/pytest.ini
@@ -0,0 +1,9 @@
+[pytest]
+markers =
+    functional: Functional tests for stuff that the user would do
+    one_dimensional: Tests in 1D
+    invalid_args: Tests for invalid argument handling
+    default_args: Tests for default argument handling
+    grid_spec: Marker to construct grid data by fixtures
+addopts =
+    --strict-markers
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..1f889d0
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,23 @@
+import numpy as np
+import pytest
+
+
+@pytest.fixture()
+def grid_data(request):
+    m = request.node.get_closest_marker("grid_spec")
+    if m is None:
+        raise ValueError("Grid data marker not defined")
+    shape = m.kwargs["shape"]
+    edges = m.kwargs["edges"]
+
+    if len(shape) == 1:
+        x = np.linspace(*edges, shape[0])
+        dx = x[1] - x[0]
+        return x, dx
+
+    axes = tuple(
+        [np.linspace(edges[k][0], edges[k][1], shape[k]) for k in range(len(shape))]
+    )
+    coords = np.meshgrid(*axes, indexing="ij")
+    spacings = [axes[k][1] - axes[k][0] for k in range(len(shape))]
+    return axes, spacings, coords
diff --git a/tests/test_diff.py b/tests/test_diff.py
index 40cb64b..329bcf4 100644
--- a/tests/test_diff.py
+++ b/tests/test_diff.py
@@ -7,19 +7,6 @@
 from findiff import Diff, Identity
 
 
-def test_partial_d_dx():
-    shape = (101,)
-    x, dx = make_grid(shape, (0, 1))
-
-    u = x**2
-    expected = 2 * x
-
-    fd = Diff(0, dx)
-    actual = fd(u)
-
-    assert_array_almost_equal(expected, actual)
-
-
 def test_partial_d_dx_periodic():
     x = np.linspace(0, 2 * np.pi, 200, endpoint=False)
     dx = x[1] - x[0]
diff --git a/tests/test_functional.py b/tests/test_functional.py
new file mode 100644
index 0000000..e9be248
--- /dev/null
+++ b/tests/test_functional.py
@@ -0,0 +1,65 @@
+import numpy as np
+import pytest
+from numpy.testing import assert_array_almost_equal
+
+from findiff import Diff
+
+pytestmark = pytest.mark.functional
+
+
+@pytest.mark.one_dimensional
+class TestDiff_1D:
+
+    @pytest.mark.grid_spec(shape=(101,), edges=(0, 1))
+    def test_diff_1d(self, grid_data):
+        x, dx = grid_data
+
+        u = x**2
+        expected = 2 * x
+
+        fd = Diff(0, dx)
+        actual = fd(u)
+
+        assert_array_almost_equal(expected, actual)
+
+    @pytest.mark.grid_spec(shape=(101,), edges=(0, 1))
+    def test_diff_1d_deferred(self, grid_data):
+        x, dx = grid_data
+
+        u = x**2
+        expected = 2 * x
+
+        fd = Diff(0)
+        fd.set_grid({0: dx})
+        actual = fd(u)
+
+        assert_array_almost_equal(expected, actual)
+
+    def test_diff_1d_deferred_called_too_early(self):
+        u = np.zeros(10)
+        fd = Diff(0)
+        with pytest.raises(TypeError, match="Unknown axis type."):
+            fd(u)
+
+    @pytest.mark.default_args
+    @pytest.mark.grid_spec(shape=(101,), edges=(0, 1))
+    def test_diff_1d_defaults(self, grid_data):
+        x, dx = grid_data
+
+        u = x**2
+        expected = 2 * x
+
+        fd = Diff()
+        fd.set_grid({0: dx})
+        actual = fd(u)
+
+        assert_array_almost_equal(expected, actual)
+
+    @pytest.mark.invalid_args
+    def test_diff_1d_invalid_args(self):
+
+        with pytest.raises(ValueError, match="Dimension must be >= 0"):
+            Diff(-1, 1)
+
+        with pytest.raises(ValueError, match="Spacing must be > 0."):
+            Diff(0, -1)