unittests: Add trace description right to the error message

test/helpers.lua

@@ -251,6 +251,28 @@ local function concat_tables(...)
   return ret
 end
 
+local function dedent(str)
+  -- find minimum common indent across lines
+  local indent = nil
+  for line in str:gmatch('[^\n]+') do
+    local line_indent = line:match('^%s+') or ''
+    if indent == nil or #line_indent < #indent then
+      indent = line_indent
+    end
+  end
+  if indent == nil or #indent == 0 then
+    -- no minimum common indent
+    return str
+  end
+  -- create a pattern for the indent
+  indent = indent:gsub('%s', '[ \t]')
+  -- strip it from the first line
+  str = str:gsub('^'..indent, '')
+  -- strip it from the remaining lines
+  str = str:gsub('[\n]'..indent, '\n')
+  return str
+end
+
 return {
   eq = eq,
   neq = neq,
@@ -265,4 +287,5 @@ return {
   hasenv = hasenv,
   which = which,
   concat_tables = concat_tables,
+  dedent = dedent,
 }