[visitor_test] Add visitor tests

Lib/fontTools/misc/visitor.py

@@ -15,7 +15,7 @@ class Visitor(object):
 
         def wrapper(method):
             assert method.__name__ == "visit"
-            for clazzes,attrs in clazzes_attrs:
+            for clazzes, attrs in clazzes_attrs:
                 if type(clazzes) != tuple:
                     clazzes = (clazzes,)
                 if type(attrs) == str:

Tests/misc/visitor_test.py

@@ -0,0 +1,61 @@
+from fontTools.misc.visitor import Visitor
+import pytest
+
+
+class A:
+    def __init__(self):
+        self.a = 1
+        self.b = [2, 3]
+        self.c = {4: 5, 6: 7}
+        self._d = 8
+        self.e = 9
+        self.f = 10
+
+
+class B:
+    def __init__(self):
+        self.a = A()
+
+
+class TestVisitor(Visitor):
+    def __init__(self):
+        self.value = []
+
+    def _add(self, s):
+        self.value.append(s)
+
+    def visitLeaf(self, obj):
+        self._add(obj)
+        super().visitLeaf(obj)
+
+
+@TestVisitor.register(A)
+def visit(self, obj):
+    self._add("A")
+
+
+@TestVisitor.register_attrs([(A, "e")])
+def visit(self, obj, attr, value):
+    self._add(attr)
+    self._add(value)
+    return False
+
+
+@TestVisitor.register(B)
+def visit(self, obj):
+    self._add("B")
+    self.visitObject(obj)
+    return False
+
+
+@TestVisitor.register_attr(B, "a")
+def visit(self, obj, attr, value):
+    self._add("B a")
+
+
+class VisitorTest(object):
+    def test_visitor(self):
+        b = B()
+        visitor = TestVisitor()
+        visitor.visit(b)
+        assert visitor.value == ["B", "B a", "A", 1, 2, 3, 5, 7, "e", 9, 10]