split node tests into standalone files

tests/node_tests/test_fft_2d.py

@@ -0,0 +1,46 @@
+import numpy as np
+from tests.node_tests._shared import make_field
+
+
+def test_fft2d():
+    from backend.nodes.fft_2d import FFT2D
+
+    node = FFT2D()
+
+    N = 64
+    y, x = np.mgrid[0:N, 0:N] / N
+    freq = 5
+    data = np.sin(2 * np.pi * freq * x)
+    field = make_field(data=data, xreal=1e-6, yreal=1e-6)
+
+    spectrum, spec_mag, spec_phase, spec_psdf = node.process(field, windowing="none", level="none")
+    assert spectrum.data.shape == (N, N)
+    assert spectrum.domain == "frequency"
+    assert spectrum.si_unit_xy == "1/m"
+    centre = N // 2
+    row = spectrum.data[centre, :]
+    peak_idx = np.argmax(row[centre + 1:]) + centre + 1
+    assert abs(peak_idx - (centre + freq)) <= 1, f"Peak at {peak_idx}, expected ~{centre + freq}"
+
+    _, spec_mag, _, _ = node.process(field, windowing="hann", level="mean")
+    assert spec_mag.data.shape == (N, N)
+    assert np.all(spec_mag.data >= 0)
+
+    _, _, spec_phase, _ = node.process(field, windowing="none", level="none")
+    assert spec_phase.data.shape == (N, N)
+    assert spec_phase.data.min() >= -np.pi - 0.01
+    assert spec_phase.data.max() <= np.pi + 0.01
+
+    _, _, _, spec_psdf = node.process(field, windowing="hamming", level="plane")
+    assert spec_psdf.data.shape == (N, N)
+    assert np.all(spec_psdf.data >= 0)
+    assert "^2" in spec_psdf.si_unit_z
+
+    const_field = make_field(data=np.ones((32, 32)) * 3.0)
+    _, spec_const, _, _ = node.process(const_field, windowing="none", level="none")
+    centre32 = 16
+    dc_val = spec_const.data[centre32, centre32]
+    assert dc_val == spec_const.data.max()
+
+    spec_bk, _, _, _ = node.process(field, windowing="blackman", level="none")
+    assert spec_bk.data.shape == (N, N)