Add a naive test of mujoco.viewer.

It just tries to import mujoco.viewer and sees that nothing crashes.

PiperOrigin-RevId: 493998120
Change-Id: I56ee696283a3c28f6c8b72de45c8fdbedb41b05f

python/mujoco/viewer_test.py

@@ -0,0 +1,28 @@
+# Copyright 2022 DeepMind Technologies Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""Extremely minimal test of mujoco.viewer that just tries to import it."""
+
+from absl.testing import absltest
+from mujoco import viewer
+
+
+class ViewerTest(absltest.TestCase):
+
+  def test_launch_function_exists(self):
+    self.assertIsNotNone(viewer.launch)
+
+
+if __name__ == '__main__':
+  absltest.main()