tests: Add a testcase for machine.PinBase class.

tests/extmod/machine_pinbase.py

@@ -0,0 +1,25 @@
+try:
+    from umachine import PinBase
+except ImportError:
+    from machine import PinBase
+
+
+class MyPin(PinBase):
+
+    def __init__(self):
+        print("__init__")
+        self.v = False
+
+    def value(self, v=None):
+        print("value:", v)
+        if v is None:
+            self.v = not self.v
+            return int(self.v)
+
+p = MyPin()
+
+print(p.value())
+print(p.value())
+print(p.value())
+p.value(1)
+p.value(0)

tests/extmod/machine_pinbase.py.exp

@@ -0,0 +1,9 @@
+__init__
+value: None
+1
+value: None
+0
+value: None
+1
+value: 1
+value: 0