test custom PRNG impl construction round trip

tests/extend_test.py

@@ -14,7 +14,9 @@
 
 from absl.testing import absltest
 
+import jax
 import jax.extend as jex
+import jax.numpy as jnp
 
 from jax._src import abstract_arrays
 from jax._src import linear_util
@@ -26,6 +28,7 @@
 
 
 class ExtendTest(jtu.JaxTestCase):
+
   def test_symbols(self):
     # Assume these are tested in random_test.py, only check equivalence
     self.assertIs(jex.random.PRNGImpl, prng.PRNGImpl)
@@ -47,5 +50,33 @@ def test_symbols(self):
     self.assertIs(jex.linear_util.wrap_init, linear_util.wrap_init)
 
 
+class RandomTest(jtu.JaxTestCase):
+
+  def test_key_make_with_custom_impl(self):
+    shape = (4, 2, 7)
+
+    def seed_rule(_):
+      return jnp.ones(shape, dtype=jnp.dtype('uint32'))
+
+    def no_rule(*args, **kwargs):
+      assert False, 'unreachable'
+
+    impl = jex.random.PRNGImpl(shape, seed_rule, no_rule, no_rule, no_rule)
+    k = jax.random.key(42, impl=impl)
+    self.assertEquals(k.shape, ())
+    self.assertEquals(impl, jax.random.key_impl(k)._impl)
+
+  def test_key_wrap_with_custom_impl(self):
+    def no_rule(*args, **kwargs):
+      assert False, 'unreachable'
+
+    shape = (4, 2, 7)
+    impl = jex.random.PRNGImpl(shape, no_rule, no_rule, no_rule, no_rule)
+    data = jnp.ones((3, *shape), dtype=jnp.dtype('uint32'))
+    k = jax.random.wrap_key_data(data, impl=impl)
+    self.assertEquals(k.shape, (3,))
+    self.assertEquals(impl, jax.random.key_impl(k)._impl)
+
+
 if __name__ == "__main__":
   absltest.main(testLoader=jtu.JaxTestLoader())