From 9c7cb473ce9bc61030360dabcb21a993f6bffffa Mon Sep 17 00:00:00 2001
From: myk002 <myk002@yahoo.com>
Date: Wed, 23 Jun 2021 14:53:02 -0700
Subject: [PATCH 1/2] add delay_until test function

---
 ci/test.lua | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/ci/test.lua b/ci/test.lua
index 07d297e3d..eb077767f 100644
--- a/ci/test.lua
+++ b/ci/test.lua
@@ -83,6 +83,19 @@ local function delay(frames)
     script.sleep(frames, 'frames')
 end
 
+-- Will call the predicate_fn every frame until it returns true. If it fails to
+-- return true before timeout_frames have elapsed, throws an error. If
+-- timeout_frames is not specified, defaults to 100.
+local function delay_until(predicate_fn, timeout_frames)
+    timeout_frames = tonumber(timeout_frames) or 100
+    repeat
+        delay()
+        if predicate_fn() then return end
+        timeout_frames = timeout_frames - 1
+    until timeout_frames < 0
+    error('timed out while waiting for predicate to return true')
+end
+
 local function clean_require(module)
     -- wrapper around require() - forces a clean load of every module to ensure
     -- that modules checking for dfhack.internal.IN_TEST at load time behave
@@ -275,6 +288,7 @@ local function build_test_env()
         expect = {},
         mock = mock,
         delay = delay,
+        delay_until = delay_until,
         require = clean_require,
         reqscript = clean_reqscript,
     }

From 7793adb888ea90c72870ee4851261f75ef975c4f Mon Sep 17 00:00:00 2001
From: myk002 <myk002@yahoo.com>
Date: Wed, 23 Jun 2021 14:55:42 -0700
Subject: [PATCH 2/2] update changelog

---
 docs/changelog.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/docs/changelog.txt b/docs/changelog.txt
index ac57e53aa..1690f8a25 100644
--- a/docs/changelog.txt
+++ b/docs/changelog.txt
@@ -69,6 +69,7 @@ changelog.txt uses a syntax similar to RST, with a few special sequences:
 - The ``test/main`` command to invoke the test harness has been renamed to just ``test``
 - DFHack unit tests must now match any output expected to be printed via ``dfhack.printerr()``
 - Fortress mode is now supported for unit tests (allowing tests that require a fortress map to be loaded) - note that these tests are skipped by continuous integration for now, pending a suitable test fortress
+- Unit tests can now use ``delay_until(predicate_fn, timeout_frames)`` to delay until a condition is met
 
 # 0.47.05-r1