std.test

Minimal assertion toolkit for sanity checks in Bop scripts.

This isn’t an xUnit clone — just the assertion primitives you’ll reach for when writing quick tests. Assertions fail by routing through the panic builtin, so the failure detail is surfaced verbatim in Err(e).message when caught by try_call. Print-based reporting is intentionally out of scope — wrap the assertion in try_call if you need “report and continue”.

Import

use std.test                                // glob
use std.test.{assert_eq, assert_near}       // selective
use std.test as t                           // aliased

Assertions

assert(cond, message)

Assert that cond is truthy. On failure, raises a runtime error — message is surfaced in the crash trace.

use std.test.{assert}
assert(1 + 1 == 2, "arithmetic still works")

assert_eq(actual, expected)

Assert two values are structurally equal (same as ==). On failure the error includes an assert_eq failed: prefix and the .inspect() of both sides.

use std.test.{assert_eq}
assert_eq([1, 2, 3].len(), 3)
assert_eq("hi".upper(), "HI")

assert_near(actual, expected, tolerance)

Assert two floats are within tolerance of each other. Use this instead of assert_eq when comparing number values subject to rounding.

use std.test.{assert_near}
assert_near((2).sqrt() * (2).sqrt(), 2, 0.0000001)

assert_raises(body)

Assert that body — a zero-arg closure — raises a runtime error. On success (no raise), the assertion itself fails. Useful for negative tests.

use std.test.{assert_raises}

assert_raises(fn() {
  let _ = 1 / 0     // expected to raise "Division by zero"
})

assert_raises(fn() {
  "not a number".to_int()
})

Under the hood, assert_raises uses try_call to observe whether body raised, so the same fatal-vs-non-fatal rules apply — a step-limit exceeded inside body propagates past the assertion instead of being caught.

Putting it together

use std.test.{assert_eq, assert_raises}

fn normalize(arr) {
  if arr.len() == 0 { return none[0] }
  let total = 0
  for x in arr { total = total + x }
  let m = total / arr.len()
  let out = []
  for x in arr { out.push(x - m) }
  return out
}

assert_eq(normalize([1, 2, 3]), [-1, 0, 1])
assert_raises(fn() { normalize([]) })      // raises on empty
print("normalize: all checks passed")