alfa-test-deprecated 0.95.0
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$ npm install @siteimprove/alfa-test-deprecated@0.95.0
Install via package.json:
"@siteimprove/alfa-test-deprecated": "0.95.0"
About this version
Thanks to the referential transparency ensured by ADR 6, unit test of Alfa code is usually very easy, simply comparing the actual result with the expected one (often as their serialisation), without need for complex setup, mocks, or other test tricks.
We're therefore implementing a very lightweight wrapper for tests.
import { test } from "@siteimprove/alfa-test";
test("My test", (t) => {
const actual = …;
t.deepEqual(actual.toJSON(), { type: …, …})
});
Sometimes, it is convenient to generate random tests with random values. The alfa-test
library is offering test controller to handle that.
- The
assertion
function that is passed totest(name, assertion)
receives additionalrng
andseed
parameters. Therng
is a function() => number
. Theseed
was used to initialize the Random Number Generator, can be used for better displaying errors and for re-playability. - The
test
function itself accepts an optionalController
object which can be used to set theseed
for the RNG, or to change the number ofiterations
to run the test (default to 1 since most tests are not random tests). TheController
object also accepts awrapper
function of type(iteration: number, rng: RNG) => RNG
that can be used to turn the random numbers into useful data, or for introspection.
The provided rng
function is guaranteed to generate the same sequence of numbers on sequential calls, if the same seed is provided by the controller. If no seed is provided, a random one will be used.
By default, each test is only run once. Use the Controller
object to change the number of iterations.
Tests that make use of the RNG are encouraged to print the seed in their error message in order to allow re-playability and investigation by feeding the failing seed back to the test.
For re-playability, use the Controller
parameter to select the seed to use (which guarantees the exact same sequence of numbers is produced), and to introspect on fine details by wrapping the RNG, e.g.,
/**
* Return a random string between "0" and "100" (inclusive).
* Print the generated number, as well as the iteration number (use for debugging).
*/
function wrapper(rng: RNG<number>, iteration: number): RNG<string> {
return () => {
const res = rng();
console.log(`On iteration ${iteration}, I generated ${res}`);
return `${res * 100}`;
};
}
test(
"Sum computes the sum of two numbers represented as strings",
(t, rng, seed) => {
// These use the post-wrapper RNG.
const a = rng();
const b = rng();
// Print the seed in error message to allow introspection.
const actual = sum(a, b, `Failed with seed ${seed}`);
t.deepEqual(actual, `${a + b}`);
},
{
wrapper,
iterations: 100,
// Set the seed for debugging, if you want to replay the same sequence of numbers.
seed: 1234,
},
);
Details
- alfa-test-deprecated
- Siteimprove
- 25 days ago
- MIT
- 2 dependencies
Assets
- alfa-test-deprecated-0.95.0.tgz
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