neverthrow-result-utils/test/ResultUtils.test.ts

Extra utilities for working with Neverthrow results

import { ResultAsync, errAsync, okAsync } from "neverthrow";

import { ResultUtils } from "../src";

describe("ResultUtils tests", () => {
	test("combine returns after each method completes", async () => {
		// Arrange
		let value = 0;
		function asyncMethod() {
			return okAsync<number, Error>(value++);
		}

		// Act
		const result = await ResultUtils.combine([
			asyncMethod(),
			asyncMethod(),
			asyncMethod(),
		]);

		// Assert
		expect(result.isErr()).toBeFalsy();
		const results = result._unsafeUnwrap();
		expect(results).toStrictEqual([0, 1, 2]);
		expect(value).toBe(3);
	});

	test("combine returns using fromPromise", async () => {
		// Arrange
		let value = 0;
		function asyncMethod() {
			return ResultAsync.fromSafePromise(
				new Promise((resolve) => {
					resolve(value++);
				})
			);
		}

		// Act
		const result = await ResultUtils.combine([
			asyncMethod(),
			asyncMethod(),
			asyncMethod(),
		]);

		// Assert
		expect(result.isErr()).toBeFalsy();
		const results = result._unsafeUnwrap();
		expect(results).toStrictEqual([0, 1, 2]);
		expect(value).toBe(3);
	});

	test("combine returns an error if one method fails", async () => {
		// Arrange
		let value = 0;
		function asyncMethod() {
			return okAsync<number, Error>(value++);
		}

		const err = new Error();
		function errorMethod() {
			return errAsync<number, Error>(err);
		}

		// Act
		const result = await ResultUtils.combine([
			asyncMethod(),
			errorMethod(),
			asyncMethod(),
		]);

		// Assert
		expect(result.isErr()).toBeTruthy();
		const errResult = result._unsafeUnwrapErr();
		expect(errResult).toBe(err);
	});

	test("executeSerially executes resultAsyncs sequentially", async () => {
		// Arrange
		let value = 0;
		const asyncMethod = () => {
			return okAsync<number, Error>(value++);
		};

		// Act
		const result = await ResultUtils.executeSerially([
			asyncMethod,
			asyncMethod,
			asyncMethod,
		]);

		// Assert
		expect(result.isErr()).toBeFalsy();
		const results = result._unsafeUnwrap();
		expect(results).toStrictEqual([0, 1, 2]);
		expect(value).toBe(3);
	});

	test("executeSerially stops executing after first error", async () => {
		// Arrange
		let value = 0;
		const asyncMethod = () => {
			return okAsync<number, Error>(value++);
		};

		const err = new Error("Error!");
		const asyncFailed = () => {
			return errAsync<number, Error>(err);
		};

		// Act
		const result = await ResultUtils.executeSerially([
			asyncMethod,
			asyncFailed,
			asyncMethod,
		]);

		// Assert
		expect(result.isErr()).toBeTruthy();
		const resultErr = result._unsafeUnwrapErr();
		expect(resultErr).toBe(err);
		expect(value).toBe(1);
	});

	test("backoffAndRetry works first time", async () => {
		// Arrange
		let value = 1;
		const asyncMethod = () => {
			return okAsync<number, Error>(value++);
		};

		// Act
		const result = await ResultUtils.backoffAndRetry(
			asyncMethod,
			[],
			10,
			1
		);

		// Assert
		expect(result.isErr()).toBeFalsy();
		const results = result._unsafeUnwrap();
		expect(results).toStrictEqual(1);
		expect(value).toBe(2);
	});

	test("backoffAndRetry works second time", async () => {
		// Arrange
		let value = 1;
		const asyncMethod = () => {
			if (value++ == 1) {
				return errAsync(new Error());
			}
			return okAsync<number, Error>(value++);
		};

		// Act
		const result = await ResultUtils.backoffAndRetry(
			asyncMethod,
			[Error],
			10,
			1
		);

		// Assert
		expect(result.isErr()).toBeFalsy();
		const results = result._unsafeUnwrap();
		expect(results).toBe(3);
		expect(value).toBe(4);
	});

	test("backoffAndRetry max retries exceeded", async () => {
		// Arrange
		let value = 0;
		const err = new Error();
		const asyncMethod = () => {
			value++;
			return errAsync(err);
		};

		// Act
		const result = await ResultUtils.backoffAndRetry(
			asyncMethod,
			[Error],
			3,
			1
		);

		// Assert
		expect(result.isErr()).toBeTruthy();
		const results = result._unsafeUnwrapErr();
		expect(results).toBe(err);
		expect(value).toBe(3);
	});

	test("backoffAndRetry unnaceptable error returned", async () => {
		// Arrange
		let value = 0;
		const err = new Error();
		const syncMethod = () => {
			value++;
			return errAsync(err);
		};

		// Act
		const result = await ResultUtils.backoffAndRetry(syncMethod, [], 10, 1);

		// Assert
		expect(result.isErr()).toBeTruthy();
		const results = result._unsafeUnwrapErr();
		expect(results).toBe(err);
		expect(value).toBe(1);
	});

	test("race returns the first resolved result", async () => {
		// Arrange
		let value = 0;
		const timedPromise = new Promise<number>((resolve, reject) => {
			setTimeout(() => {
				value = 2;
				resolve(2);
			}, 500);
		});
		const timedResult = ResultAsync.fromPromise(
			timedPromise,
			(e) => e as Error
		);
		const asyncMethod = () => {
			return okAsync<number, Error>(value++);
		};

		// Act
		const result = await ResultUtils.race([timedResult, asyncMethod()]);

		// Assert
		expect(result.isErr()).toBeFalsy();
		const resultWrap = result._unsafeUnwrap();
		expect(resultWrap).toStrictEqual(0);
		expect(value).toBe(1);
	});

	test("race stops at the first resolved promise", async () => {
		// Arrange
		let value = 0;
		const timedPromise = new Promise<number>((resolve, reject) => {
			setTimeout(() => {
				value = 1;
				resolve(1);
			}, 500);
		});
		const timedResult = ResultAsync.fromPromise(
			timedPromise,
			(e) => e as Error
		);

		const timedPromise2 = new Promise<number>((resolve, reject) => {
			setTimeout(() => {
				resolve(2);
			}, 100);
		});
		const timedResult2 = ResultAsync.fromPromise(
			timedPromise2,
			(e) => e as Error
		);

		// Act
		const result = await ResultUtils.race([timedResult, timedResult2]);

		// Assert
		expect(result.isErr()).toBeFalsy();
		const resultWrap = result._unsafeUnwrap();
		expect(resultWrap).toStrictEqual(2);
		expect(value).toBe(0);
	});

	test("filter() returns successfully when no callback has errors", async () => {
		// Arrange
		const sourceArr = [1, 2, 3, 4, 5, 6];

		// Act
		const result = await ResultUtils.filter<number, Error>(
			sourceArr,
			(val) => {
				if (val < 3) {
					return okAsync(true);
				}
				return okAsync(false);
			}
		);

		// Assert
		expect(result).toBeDefined();
		expect(result.isOk()).toBeTruthy();
		const filteredResults = result._unsafeUnwrap();
		expect(filteredResults.length).toBe(2);
		expect(filteredResults).toStrictEqual([1, 2]);
	});

	test("filter() returns an error when a single callback has errors", async () => {
		// Arrange
		const sourceArr = [1, 2, 3, 4, 5, 6];

		// Act
		const result = await ResultUtils.filter<number, Error>(
			sourceArr,
			(val) => {
				if (val > 3) {
					return errAsync(new Error());
				}
				return okAsync(false);
			}
		);

		// Assert
		expect(result).toBeDefined();
		expect(result.isErr()).toBeTruthy();
	});

	test("map() returns successfully when no callback has errors", async () => {
		// Arrange
		const sourceArr = [1, 2, 3, 4, 5, 6];

		// Act
		const result = await ResultUtils.map(sourceArr, (val) => {
			return okAsync<string, Error>((val * 10).toString());
		});

		// Assert
		expect(result).toBeDefined();
		expect(result.isOk()).toBeTruthy();
		const filteredResults = result._unsafeUnwrap();
		expect(filteredResults.length).toBe(6);
		expect(filteredResults).toStrictEqual([
			"10",
			"20",
			"30",
			"40",
			"50",
			"60",
		]);
	});

	test("map() returns an error when a single callback has errors", async () => {
		// Arrange
		const sourceArr = [1, 2, 3, 4, 5, 6];

		// Act
		const result = await ResultUtils.map(sourceArr, (val) => {
			if (val > 3) {
				return errAsync(new Error());
			}
			return okAsync<string, Error>((val * 10).toString());
		});

		// Assert
		expect(result).toBeDefined();
		expect(result.isErr()).toBeTruthy();
	});
});