local M = {}

function M.same(expected, actual, message)
  if expected ~= actual then
    error((message or "values differ")
      .. ": expected " .. tostring(expected)
      .. ", got " .. tostring(actual), 2)
  end
end

function M.truthy(value, message)
  if not value then
    error(message or "value must be true", 2)
  end
end

function M.falsy(value, message)
  if value then
    error(message or "value must be false", 2)
  end
end

function M.fails(body, expected_text)
  local ok, failure = pcall(body)
  if ok then
    error("operation must fail", 2)
  end
  if expected_text and not tostring(failure):find(expected_text, 1, true) then
    error("failure does not contain '" .. expected_text .. "': " .. tostring(failure), 2)
  end
end

function M.list_same(expected, actual)
  M.same(#expected, #actual, "list lengths differ")
  for index = 1, #expected do
    M.same(expected[index], actual[index], "list item " .. tostring(index) .. " differs")
  end
end

return M