added unit test for param tie at the kernel level

GPy/testing/kernel_tests.py

@@ -0,0 +1,23 @@
+# Copyright (c) 2012, GPy authors (see AUTHORS.txt).
+# Licensed under the BSD 3-clause license (see LICENSE.txt)
+
+import unittest
+import numpy as np
+import GPy
+
+class KernelTests(unittest.TestCase):
+    def test_kerneltie(self):
+        K = GPy.kern.rbf(5, ARD=True)
+        K.tie_param('[01]')
+        K.constrain_fixed('2')
+        X = np.random.rand(5,5)
+        Y = np.ones((5,1))
+        m = GPy.models.GP_regression(X,Y,K)
+        print m
+        self.assertTrue(m.checkgrad())
+
+
+
+if __name__ == "__main__":
+    print "Running unit tests, please be (very) patient..."
+    unittest.main()