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5803cc9172
* BREAKING(assert): remove `assert` from module names * work * fix * work * work * tweaks * fix
56 lines
1.9 KiB
TypeScript
56 lines
1.9 KiB
TypeScript
// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
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// This module is browser compatible.
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import { AssertionError } from "./assertion_error.ts";
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/**
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* Make an assertion that `actual` and `expected` are almost equal numbers
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* through a given tolerance. It can be used to take into account IEEE-754
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* double-precision floating-point representation limitations. If the values
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* are not almost equal then throw.
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*
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* The default tolerance is one hundred thousandth of a percent of the
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* expected value.
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*
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* @example Usage
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* ```ts no-eval
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* import { assertAlmostEquals } from "@std/assert";
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*
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* assertAlmostEquals(0.01, 0.02); // Throws
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* assertAlmostEquals(1e-8, 1e-9); // Throws
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* assertAlmostEquals(1.000000001e-8, 1.000000002e-8); // Doesn't throw
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* assertAlmostEquals(0.01, 0.02, 0.1); // Doesn't throw
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* assertAlmostEquals(0.1 + 0.2, 0.3, 1e-16); // Doesn't throw
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* assertAlmostEquals(0.1 + 0.2, 0.3, 1e-17); // Throws
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* ```
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*
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* @param actual The actual value to compare.
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* @param expected The expected value to compare.
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* @param tolerance The tolerance to consider the values almost equal. The
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* default is one hundred thousandth of a percent of the expected value.
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* @param msg The optional message to include in the error.
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*/
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export function assertAlmostEquals(
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actual: number,
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expected: number,
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tolerance?: number,
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msg?: string,
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) {
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if (Object.is(actual, expected)) {
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return;
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}
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const delta = Math.abs(expected - actual);
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if (tolerance === undefined) {
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tolerance = isFinite(expected) ? Math.abs(expected * 1e-7) : 1e-7;
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}
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if (delta <= tolerance) {
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return;
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}
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const msgSuffix = msg ? `: ${msg}` : ".";
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const f = (n: number) => Number.isInteger(n) ? n : n.toExponential();
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throw new AssertionError(
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`Expected actual: "${f(actual)}" to be close to "${f(expected)}": \
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delta "${f(delta)}" is greater than "${f(tolerance)}"${msgSuffix}`,
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);
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}
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