Usage:

Clone or copy the warbler file and license into your codebase. Does wren have a package manager yet? Is that a thing?

Create a test file and import/use the Test class like so:

import "warbler" for Test

System.print("Testing...")
var test = Test.new("Reality")

test.describe("Everything is sane") {
  test.assert(true, true, "booleans work")
}

test.describe("The world is upside down") {
  test.assert(true, true)
}

Test output:

Testing Reality.
Describe: Everything is sane
GREAT SUCCESS: booleans work
Describe: The world is upside down
FAIL: true was not false in Reality.