test: add output shape test

Author: jokasimr

tests/reflectometry/__init__.py

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+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright (c) 2025 Scipp contributors (https://github.com/scipp)

tests/reflectometry/normalization_test.py

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+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright (c) 2025 Scipp contributors (https://github.com/scipp)
+import numpy as np
+import pytest
+import scipp as sc
+
+from ess.reflectometry.normalization import reduce_sample_over_zw
+
+
+@pytest.fixture
+def sample(request):
+    n = 50
+    da = sc.DataArray(
+        data=sc.ones(dims=('events',), shape=(n,)),
+        coords={
+            'wavelength': sc.linspace('events', 1, 5, n),
+            'wire': sc.array(dims=('events',), values=np.random.randint(0, 5, n)),
+            'stripe': sc.array(dims=('events',), values=np.random.randint(0, 10, n)),
+        },
+    )
+    return da.group('wire', 'stripe')
+
+
+@pytest.fixture
+def reference(request):
+    n = 50
+    da = sc.DataArray(
+        data=sc.ones(dims=('events',), shape=(n,)),
+        coords={
+            'wavelength': sc.linspace('events', 1, 5, n),
+            'wire': sc.array(dims=('events',), values=np.random.randint(0, 5, n)),
+            'stripe': sc.array(dims=('events',), values=np.random.randint(0, 10, n)),
+        },
+    )
+    return da.group('wire').bin(wavelength=2).bins.sum()
+
+
+def test_reduce_sample_over_zw_when_data_not_dimensionless(sample, reference):
+    sample = sample.copy(deep=True)
+    sample.bins.unit = '1/s'
+    reduce_sample_over_zw(
+        sample,
+        reference,
+        reference.coords['wavelength'],
+    )
+
+
+def test_reduce_sample_over_zw_has_expected_coords(sample, reference):
+    r = reduce_sample_over_zw(
+        sample,
+        reference,
+        reference.coords['wavelength'],
+    )
+    assert r.dims == reference.dims
+    assert r.shape == reference.shape
+    assert not (sample.bins is None) ^ (r.bins is None)