diff --git a/ci/test.lua b/ci/test.lua
index 07d297e3d..5a606476f 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
@@ -245,7 +258,6 @@ local function wrap_expect(func, private)
         orig_printerr('Check failed! ' .. (msg or '(no message)'))
         -- Generate a stack trace with all function calls in the same file as the caller to expect.*()
         -- (this produces better stack traces when using helpers in tests)
-        -- Skip any frames corresponding to C calls, which could be pcall() / with_finalize()
         local frame = 2
         local caller_src
         while true do
@@ -254,10 +266,9 @@ local function wrap_expect(func, private)
             if not caller_src then
                 caller_src = info.short_src
             end
-            if info.what == 'Lua' then
-                if info.short_src ~= caller_src then
-                    break
-                end
+            -- Skip any frames corresponding to C calls, or Lua functions defined in another file
+            -- these could include pcall(), with_finalize(), etc.
+            if info.what == 'Lua' and info.short_src == caller_src then
                 orig_printerr(('  at %s:%d'):format(info.short_src, info.currentline))
             end
             frame = frame + 1
@@ -275,6 +286,7 @@ local function build_test_env()
         expect = {},
         mock = mock,
         delay = delay,
+        delay_until = delay_until,
         require = clean_require,
         reqscript = clean_reqscript,
     }
diff --git a/docs/changelog.txt b/docs/changelog.txt
index ac57e53aa..2da577260 100644
--- a/docs/changelog.txt
+++ b/docs/changelog.txt
@@ -51,6 +51,7 @@ changelog.txt uses a syntax similar to RST, with a few special sequences:
 - `embark-assistant`: slightly improved performance of surveying and improved code a little
 
 ## Lua
+- new string utility function: ``string:wrap(width)`` wraps a string at space-separated word boundaries
 - ``gui.Painter``: fixed error when calling ``viewport()`` method
 - `reveal`: now exposes ``unhideFlood(pos)`` functionality to Lua
 - ``utils.processArgsGetopt()``: now returns negative numbers (e.g. ``-10``) in the list of positional parameters instead of treating it as an option string equivalent to ``-1 -0``
@@ -69,6 +70,7 @@ 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
 
diff --git a/library/lua/dfhack.lua b/library/lua/dfhack.lua
index d1e664af7..bca2cc895 100644
--- a/library/lua/dfhack.lua
+++ b/library/lua/dfhack.lua
@@ -369,6 +369,43 @@ function string:endswith(suffix)
     return self:sub(-#suffix) == suffix or #suffix == 0
 end
 
+-- Inserts newlines into a string so no individual line exceeds the given width.
+-- Lines are split at space-separated word boundaries. Any existing newlines are
+-- kept in place. If a single word is longer than width, it is split over
+-- multiple lines.
+function string:wrap(width)
+    local wrapped_text = {}
+    for line in self:gmatch('[^\n]*') do
+        local line_start_pos = 1
+        local wrapped_line = line:gsub(
+            '%s*()(%S+)()',
+            function(start_pos, word, end_pos)
+                -- word fits within the current line
+                if end_pos - line_start_pos <= width then return end
+                -- word needs to go on the next line, but is not itself longer
+                -- than the specified width
+                if #word <= width then
+                    line_start_pos = start_pos
+                    return '\n' .. word
+                end
+                -- word is too long to fit on one line and needs to be split up
+                local num_chars, str = 0, start_pos == 1 and '' or '\n'
+                repeat
+                    local word_frag = word:sub(num_chars + 1, num_chars + width)
+                    str = str .. word_frag
+                    num_chars = num_chars + #word_frag
+                    if num_chars < #word then
+                        str = str .. '\n'
+                    end
+                    line_start_pos = start_pos + num_chars
+                until end_pos - line_start_pos <= width
+                return str .. word:sub(num_chars + 1)
+            end)
+        table.insert(wrapped_text, wrapped_line)
+    end
+    return table.concat(wrapped_text, '\n')
+end
+
 -- String conversions
 
 function dfhack.persistent:__tostring()
diff --git a/library/lua/test_util/expect.lua b/library/lua/test_util/expect.lua
index deca8c44f..9a8d16903 100644
--- a/library/lua/test_util/expect.lua
+++ b/library/lua/test_util/expect.lua
@@ -24,11 +24,11 @@ function expect.nil_(value, comment)
 end
 
 function expect.eq(a, b, comment)
-    return a == b, comment, ('%s ~= %s'):format(a, b)
+    return a == b, comment, ('"%s" ~= "%s"'):format(a, b)
 end
 
 function expect.ne(a, b, comment)
-    return a ~= b, comment, ('%s == %s'):format(a, b)
+    return a ~= b, comment, ('"%s" == "%s"'):format(a, b)
 end
 
 function expect.lt(a, b, comment)
diff --git a/test/library/string.lua b/test/library/string.lua
new file mode 100644
index 000000000..58bd2d6e4
--- /dev/null
+++ b/test/library/string.lua
@@ -0,0 +1,33 @@
+-- tests string functions added by dfhack.lua
+
+function test.startswith()
+    expect.true_(('abcd'):startswith(''))
+    expect.true_(('abcd'):startswith('abc'))
+    expect.false_(('abcd'):startswith('bcd'))
+    expect.false_(('abcd'):startswith('abcde'))
+
+    expect.true_((''):startswith(''))
+    expect.false_((''):startswith('a'))
+end
+
+function test.endswith()
+    expect.true_(('abcd'):endswith(''))
+    expect.true_(('abcd'):endswith('bcd'))
+    expect.false_(('abcd'):endswith('abc'))
+    expect.false_(('abcd'):endswith('zabcd'))
+
+    expect.true_((''):endswith(''))
+    expect.false_((''):endswith('a'))
+end
+
+function test.wrap()
+    expect.eq('hello world', ('hello world'):wrap(20))
+    expect.eq('hello   world', ('hello   world'):wrap(20))
+    expect.eq('hello world\nhow are you?',('hello world how are you?'):wrap(12))
+    expect.eq('hello\nworld', ('hello world'):wrap(5))
+    expect.eq('hello\nworld', ('hello        world'):wrap(5))
+    expect.eq('hello\nworld', ('hello world'):wrap(8))
+    expect.eq('hel\nlo\nwor\nld', ('hello world'):wrap(3))
+    expect.eq('hel\nloo\nwor\nldo', ('helloo  worldo'):wrap(3))
+    expect.eq('', (''):wrap(10))
+end