Fix conflict_set.py bug, and add full inner words test

Apparently all bytes were 0

conflict_set.py

@@ -28,39 +28,38 @@ class Result(enum.Enum):
 
 
 def write(begin: bytes, end: Optional[bytes] = None) -> WriteRange:
-    b = (ctypes.c_ubyte * len(begin))()
-    b.value = begin
+    b = (ctypes.c_ubyte * len(begin)).from_buffer(bytearray(begin))
+
     if end is None:
         e = (ctypes.c_ubyte * 0)()
-        e.value = b""
     else:
-        e = (ctypes.c_ubyte * len(end))()
-        e.value = end
+        e = (ctypes.c_ubyte * len(end)).from_buffer(bytearray(end))
     return WriteRange(_Key(b, len(b)), _Key(e, len(e)))
 
 
 def read(version: int, begin: bytes, end: Optional[bytes] = None) -> ReadRange:
-    b = (ctypes.c_ubyte * len(begin))()
-    b.value = begin
+    b = (ctypes.c_ubyte * len(begin)).from_buffer(bytearray(begin))
     if end is None:
         e = (ctypes.c_ubyte * 0)()
-        e.value = b""
     else:
-        e = (ctypes.c_ubyte * len(end))()
-        e.value = end
+        e = (ctypes.c_ubyte * len(end)).from_buffer(bytearray(end))
     return ReadRange(_Key(b, len(b)), _Key(e, len(e)), version)
 
 
 class ConflictSet:
-    def __init__(self, version: int = 0, implementation: Optional[str] = None) -> None:
+    def __init__(
+        self,
+        version: int = 0,
+        build_dir: Optional[str] = None,
+        implementation: Optional[str] = None,
+    ) -> None:
         self._lib = None
+        if build_dir is None:
+            build_dir = os.path.dirname(__file__) + "/build"
         if implementation is None:
             implementation = "radix_tree"
         for f in (
-            os.path.dirname(__file__)
-            + "/build/"
-            + implementation
-            + "/libconflict-set.so.0",
+            build_dir + "/" + implementation + "/libconflict-set.so.0",
             os.path.dirname(__file__)
             + "/build/"
             + implementation