Adds unit test to check all pre-included asset configs work as expected (#511)

# Description

This MR adds a test to check all the asset configurations in the
`omni.isaac.orbit_assets` class work as expected. This is useful since
we keep adding new checks and updates. It is good to automatically know
that the assets can be initialized successfully.

## Type of change

- New feature (non-breaking change which adds functionality)

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./orbit.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] I have run all the tests with `./orbit.sh --test` and they pass
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

Author: Mayankm96

source/extensions/omni.isaac.orbit_assets/omni/isaac/orbit_assets/ridgeback_franka.py

@@ -34,7 +34,7 @@
             "panda_joint3": 0.0,
             "panda_joint4": -2.810,
             "panda_joint5": 0.0,
-            "panda_joint6": 3.037,
+            "panda_joint6": 2.0,
             "panda_joint7": 0.741,
             # tool
             "panda_finger_joint.*": 0.035,
@@ -76,8 +76,8 @@
 
 The following control configuration is used:
 
-* Base: velocity control with damping
-* Arm: position control with damping (contains default position offsets)
-* Hand: mimic control
+* Base: velocity control
+* Arm: position control with damping
+* Hand: position control with damping
 
 """

source/extensions/omni.isaac.orbit_assets/test/test_valid_configs.py

@@ -0,0 +1,71 @@
+# Copyright (c) 2022-2024, The ORBIT Project Developers.
+# All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+# ignore private usage of variables warning
+# pyright: reportPrivateUsage=none
+
+"""Launch Isaac Sim Simulator first."""
+
+from omni.isaac.orbit.app import AppLauncher, run_tests
+
+# launch the simulator
+app_launcher = AppLauncher(headless=True)
+simulation_app = app_launcher.app
+
+
+"""Rest everything follows."""
+
+import unittest
+
+import omni.isaac.orbit_assets as orbit_assets  # noqa: F401
+
+from omni.isaac.orbit.assets import AssetBase, AssetBaseCfg
+from omni.isaac.orbit.sensors import SensorBase, SensorBaseCfg
+from omni.isaac.orbit.sim import build_simulation_context
+
+
+class TestValidEntitiesConfigs(unittest.TestCase):
+    """Test cases for all registered entities configurations."""
+
+    @classmethod
+    def setUpClass(cls):
+        # load all registered entities configurations from the module
+        cls.registered_entities: dict[str, AssetBaseCfg | SensorBaseCfg] = {}
+        # inspect all classes from the module
+        for obj_name in dir(orbit_assets):
+            obj = getattr(orbit_assets, obj_name)
+            # store all registered entities configurations
+            if isinstance(obj, (AssetBaseCfg, SensorBaseCfg)):
+                cls.registered_entities[obj_name] = obj
+        # print all existing entities names
+        print(">>> All registered entities:", list(cls.registered_entities.keys()))
+
+    """
+    Test fixtures.
+    """
+
+    def test_asset_configs(self):
+        """Check all registered asset configurations."""
+        # iterate over all registered assets
+        for asset_name, entity_cfg in self.registered_entities.items():
+            for device in ("cuda:0", "cpu"):
+                with self.subTest(asset_name=asset_name, device=device):
+                    with build_simulation_context(device=device, auto_add_lighting=True) as sim:
+                        # print the asset name
+                        print(">>> Testing entities:", asset_name)
+                        # name the prim path
+                        entity_cfg.prim_path = "/World/asset"
+                        # create the asset / sensors
+                        entity: AssetBase | SensorBase = entity_cfg.class_type(entity_cfg)  # type: ignore
+
+                        # play the sim
+                        sim.reset()
+
+                        # check asset is initialized successfully
+                        self.assertTrue(entity._is_initialized)
+
+
+if __name__ == "__main__":
+    run_tests()

source/extensions/omni.isaac.orbit_tasks/omni/isaac/orbit_tasks/classic/ant/ant_env_cfg.py

@@ -65,7 +65,13 @@ class MySceneCfg(InteractiveSceneCfg):
         ),
         init_state=ArticulationCfg.InitialStateCfg(
             pos=(0.0, 0.0, 0.5),
-            joint_pos={".*": 0.0},
+            joint_pos={
+                ".*_leg": 0.0,
+                "front_left_foot": 0.785398,  # 45 degrees
+                "front_right_foot": -0.785398,
+                "left_back_foot": -0.785398,
+                "right_back_foot": 0.785398,
+            },
         ),
         actuators={
             "body": ImplicitActuatorCfg(