Add tests

Author: devmotion

test/trainable.jl

@@ -36,12 +36,22 @@
     kr = RationalQuadraticKernel(α=α)
     test_params(kr, ([α],))
 
+    A = rand(3, 3)
+    km = PiecewisePolynomialKernel(v=1, maha=A)
+    test_params(km, (A,))
+
+    km = MahalanobisKernel(A)
+    test_params(km, (A,))
+
     k = km + kc
     test_params(k, (km, kc))
 
     k = km * kc
     test_params(k, (km, kc))
 
+    k = TensorProduct(km, kc)
+    test_params(k, (km, kc))
+
     s = 2.0
     k = transform(km, s)
     test_params(k, (km, [s]))