evaluate wait_cond before any wait in until(_not)

Author: alexcjohnson

Diff for: dash/testing/wait.py

@@ -15,7 +15,7 @@ def until(
     poll=0.1,
     msg="expected condition not met within timeout",
 ):  # noqa: C0330
-    res = None
+    res = wait_cond()
     logger.debug(
         "start wait.until with method, timeout, poll => %s %s %s",
         wait_cond,
@@ -36,7 +36,7 @@ def until(
 def until_not(
     wait_cond, timeout, poll=0.1, msg="expected condition met within timeout"
 ):  # noqa: C0330
-    res = True
+    res = wait_cond()
     logger.debug(
         "start wait.until_not method, timeout, poll => %s %s %s",
         wait_cond,