Initial commit. Stage one work done.

tests/test_api.py

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+"""API surface tests: registry integrity and the pylibxc-compatible shim."""
+
+import numpy as np
+import pytest
+
+import funxc
+from funxc.libxc_compat import LibXCFunctional
+
+
+def test_registry_specs_wellformed():
+    for fid, spec in funxc.REGISTRY.items():
+        assert spec.id == fid
+        assert spec.family in ("lda", "gga", "mgga")
+        assert spec.kind in ("x", "c", "xc", "k")
+        assert spec.libxc_id > 0
+        assert spec.kernel_fn is not None
+        assert spec.doi
+
+
+def test_get_spec_is_case_insensitive():
+    assert funxc.get_spec("gga_x_pbe") is funxc.get_spec("GGA_X_PBE")
+    assert funxc.get_spec("XC_GGA_X_PBE") is funxc.get_spec("GGA_X_PBE")
+    with pytest.raises(KeyError):
+        funxc.get_spec("GGA_X_DOES_NOT_EXIST")
+
+
+def test_shim_polarized_shapes():
+    f = LibXCFunctional("gga_x_pbe", "polarized")
+    n = 4
+    rng = np.random.default_rng(0)
+    inp = {
+        "rho": rng.uniform(0.1, 1.0, (n, 2)),
+        "sigma": rng.uniform(0.0, 0.5, (n, 3)),
+    }
+    out = f.compute(inp)
+    assert out["zk"].shape == (n, 1)
+    assert out["vrho"].shape == (n, 2)
+    assert out["vsigma"].shape == (n, 3)
+
+
+def test_shim_unpolarized_shapes_and_flat_input():
+    f = LibXCFunctional("lda_x", 1)
+    rho = np.linspace(0.1, 2.0, 5)
+    out = f.compute({"rho": rho})
+    assert out["zk"].shape == (5, 1)
+    assert out["vrho"].shape == (5, 1)
+    out_exc_only = f.compute({"rho": rho}, do_vxc=False)
+    assert set(out_exc_only) == {"zk"}
+
+
+def test_shim_mgga_shapes():
+    f = LibXCFunctional("mgga_x_lta", "polarized")
+    n = 4
+    rng = np.random.default_rng(1)
+    inp = {
+        "rho": rng.uniform(0.1, 1.0, (n, 2)),
+        "sigma": rng.uniform(0.0, 0.5, (n, 3)),
+        "lapl": rng.uniform(-1.0, 1.0, (n, 2)),
+        "tau": rng.uniform(0.1, 1.0, (n, 2)),
+    }
+    out = f.compute(inp)
+    assert out["zk"].shape == (n, 1)
+    assert out["vrho"].shape == (n, 2)
+    assert out["vsigma"].shape == (n, 3)
+    assert out["vlapl"].shape == (n, 2)
+    assert out["vtau"].shape == (n, 2)
+    # LTA has no lapl dependence: vlapl must be exactly zero
+    assert np.all(out["vlapl"] == 0.0)
+
+
+def test_shim_metadata():
+    f = LibXCFunctional("gga_c_lyp", "polarized")
+    assert f.get_number() == 131
+    assert f.get_family() == "gga"
+
+
+def test_composition_blyp():
+    """X and C functionals compose additively (BLYP = B88 + LYP)."""
+    rho = np.array([[0.4, 0.3]])
+    sigma = np.array([[0.02, 0.01, 0.015]])
+    b88 = funxc.functional("GGA_X_B88").exc(rho, sigma)
+    lyp = funxc.functional("GGA_C_LYP").exc(rho, sigma)
+    total = np.asarray(b88) + np.asarray(lyp)
+    assert np.all(np.isfinite(total)) and total[0] < 0