assert

Tiny assertion helpers for writing tests in Bern.

import assert

Each assertion returns a string ending in PASS or FAIL, named so you can read a column of results at a glance. They never throw - you collect and print the outcomes yourself.

Equality

assert_equals(name, got, expected) → string

Compare two values with ==.

assert_equals("Addition test", 2 + 2, 4)
-- Output: "Addition test PASS"

assert_equals("Wrong test", 2 + 2, 5)
-- Output: "Wrong test FAIL"

Approximate equality

approx_eq(a, b, tolerance) → boolean

Whether a and b are within tolerance of each other - the helper behind assert_approx.

approx_eq(3.14159, 3.14, 0.01)
-- Output: true

assert_approx(name, got, expected, tolerance) → string

Like assert_equals, but passes when the two numbers are close enough - the right tool for floating-point results.

assert_approx("Pi test", 3.14159, 3.14, 0.01)
-- Output: "Pi test PASS"

Putting it together

A test file usually gathers a list of results and prints them. Here assert teams up with math to check a couple of computations at once:

A small test suite

import assert
import core
import math

results = [
    assert_equals("sum",      sum([1, 2, 3, 4]), 10),
    assert_equals("reverse",  reverse([1, 2, 3]), [3, 2, 1]),
    assert_approx("sqrt(2)",  sqrt(2), 1.41421, 0.001),
    assert_approx("sin(0)",   sin(0), 0.0, 0.0001)
]

loop r : results do
    r
end
-- Output:
-- "sum PASS"
-- "reverse PASS"
-- "sqrt(2) PASS"
-- "sin(0) PASS"