tests: Add simple NodePath tests using PyTest

These tests were converted from the tests branch with some changes:

  * Convert from unittest to PyTest
  * Update code to use new API (LVector3 instead of Vec3, properties, etc.)

tests/pgraph/test_nodepath.py

@@ -0,0 +1,81 @@
+def test_nodepath_empty():
+    """Tests NodePath behavior for empty NodePaths."""
+    from panda3d.core import NodePath
+
+    empty = NodePath('np')
+
+    assert empty.get_pos() == (0, 0, 0)
+    assert empty.get_hpr() == (0, 0, 0)
+    assert empty.get_scale() == (1, 1, 1)
+
+def test_nodepath_parent():
+    """Tests NodePath.reparentTo()."""
+    from panda3d.core import NodePath
+
+    np1 = NodePath('np')
+    np2 = NodePath('np')
+
+    assert np1.parent is None
+    assert np2.parent is None
+
+    np1.reparentTo(np2)
+
+    assert np1.parent == np2
+    assert np2.parent is None
+
+def test_nodepath_transform_changes():
+    """Tests that NodePath applies transform changes to its managed node."""
+    from panda3d.core import NodePath
+
+    np = NodePath('np')
+    assert np.get_pos() == (0, 0, 0)
+    assert np.get_hpr() == (0, 0, 0)
+    assert np.get_scale() == (1, 1, 1)
+
+    np.set_pos(1, 2, 3)
+    assert np.get_pos() == (1, 2, 3)
+    assert np.node().get_transform().get_pos() == (1, 2, 3)
+
+def test_nodepath_transform_composition():
+    """Tests that NodePath composes transform states according to the path it holds."""
+    from panda3d.core import PandaNode, NodePath, LPoint3, LVector3
+
+    # Create 3 PandaNodes, and give each some interesting transform state:
+    node1 = PandaNode('node1')
+    node2 = PandaNode('node2')
+    node3 = PandaNode('node3')
+
+    node1.set_transform(node1.get_transform().set_pos(LPoint3(0, 0, 1)).set_hpr(LVector3(90, 0, -90)))
+    node2.set_transform(node2.get_transform().set_pos(LPoint3(0, 1, 0)).set_hpr(LVector3(180, 180, 0)))
+    node3.set_transform(node3.get_transform().set_pos(LPoint3(1, 0, 0)).set_hpr(LVector3(270, 0, 270)))
+
+    # node3 is going to be attached under both node1 and node2 and we will
+    # hold a path both ways:
+    node1.add_child(node3)
+    node2.add_child(node3)
+
+    assert len(node1.children) == 1
+    assert len(node2.children) == 1
+    assert len(node3.children) == 0
+    assert len(node1.parents) == 0
+    assert len(node2.parents) == 0
+    assert len(node3.parents) == 2
+
+    # np1 is the path to node3 via node1:
+    np1 = NodePath(node1).children[0]
+    # np2 is the path to node3 via node2:
+    np2 = NodePath(node2).children[0]
+
+    # Both should point to node3:
+    assert np1.node() == node3
+    assert np2.node() == node3
+
+    # However if we ask for the net transform to node3, it should compose:
+    assert np1.get_transform(NodePath()) == node1.get_transform().compose(node3.get_transform())
+    assert np2.get_transform(NodePath()) == node2.get_transform().compose(node3.get_transform())
+
+    # If we ask for np1 RELATIVE to np2, it should compose like so:
+    leg1 = node2.get_transform().compose(node3.get_transform())
+    leg2 = node1.get_transform().compose(node3.get_transform())
+    relative_transform = leg1.get_inverse().compose(leg2)
+    assert np1.get_transform(np2) == relative_transform