auto gfrad test added

tests/test_autograd.py

@@ -0,0 +1,38 @@
+from copapy import variable, grad
+import copapy as cp
+import pytest
+
+
+def test_autograd():
+    # Validate against micrograd results from Andrej Karpathy
+    # https://github.com/karpathy/micrograd/blob/master/test/test_engine.py
+    a = variable(-4.0)
+    b = variable(2.0)
+    c = a + b
+    d = a * b + b**3
+    c += c + 1
+    c += 1 + c + (-a)
+    d += d * 2 + cp.relu(b + a)
+    d += 3 * d + cp.relu(b - a)
+    e = c - d
+    f = e**2
+    g = f / 2.0
+    g += 10.0 / f
+
+    dg = grad(g, (a, b))
+
+    tg = cp.Target()
+    tg.compile(g, dg)
+    tg.run()
+
+
+    print(f"g = {tg.read_value(g)}")
+    print(f"dg/da = {tg.read_value(dg[0])}   grad:{dg[0]}    val:{a} = {tg.read_value(a)}")
+    print(f"dg/db = {tg.read_value(dg[1])}   grad:{dg[1]}    val:{b} = {tg.read_value(b)}")
+
+    assert pytest.approx(dg[0], abs=1e-4) == 138.83381  # pyright: ignore[reportUnknownMemberType]
+    assert pytest.approx(dg[1], abs=1e-4) == 645.57725  # pyright: ignore[reportUnknownMemberType]
+
+
+if __name__ == "__main__":
+    test_autograd()