tests: Add property test.

tests/basics/property.py

+class A:
+    def __init__(self, x):
+        self._x = x
+
+    @property
+    def x(self):
+        print("x get")
+        return self._x
+
+a = A(1)
+print(a.x)
+
+try:
+    a.x = 2
+except AttributeError:
+    print("AttributeError")
+
+class B:
+    def __init__(self, x):
+        self._x = x
+
+    def xget(self):
+        print("x get")
+        return self._x
+
+    def xset(self, value):
+        print("x set")
+        self._x = value
+
+    x = property(xget, xset)
+
+b = B(3)
+print(b.x)
+b.x = 4
+print(b.x)
+
+class C:
+    def __init__(self, x):
+        self._x = x
+
+    @property
+    def x(self):
+        print("x get")
+        return self._x
+
+    @x.setter
+    def x(self, value):
+        print("x set")
+        self._x = value
+
+c = C(5)
+print(c.x)
+c.x = 6
+print(c.x)