TypeScript-friendly testing utilities.
npm install @clipboard-health/testing-core
expect
helpersJest's expect(...).toBeDefined()
does not narrow types.
This gives a type error:
const value = getValue(); // returns 'string | undefined'
expect(value).toBeDefined();
const { length } = value;
// ^? Property 'length' does not exist on type 'string | undefined'.
This library's helpers narrow types:
import { strictEqual } from "node:assert/strict";
import { expectToBeDefined } from "@clipboard-health/testing-core";
function getValue(): string | undefined {
return "hi";
}
const value = getValue();
expectToBeDefined(value);
// Narrowed to `string`
const { length } = value;
strictEqual(length, 2);
import { strictEqual } from "node:assert/strict";
import { expectToBeLeft } from "@clipboard-health/testing-core";
import { either as E } from "@clipboard-health/util-ts";
function divide(numerator: number, denominator: number): E.Either<string, number> {
if (denominator === 0) {
return E.left("Cannot divide by zero");
}
return E.right(numerator / denominator);
}
const value = divide(10, 0);
expectToBeLeft(value);
// Narrowed to Left
strictEqual(value.left, "Cannot divide by zero");
import { strictEqual } from "node:assert/strict";
import { expectToBeRight } from "@clipboard-health/testing-core";
import { either as E } from "@clipboard-health/util-ts";
function divide(numerator: number, denominator: number): E.Either<string, number> {
if (denominator === 0) {
return E.left("Cannot divide by zero");
}
return E.right(numerator / denominator);
}
const value = divide(10, 2);
expectToBeRight(value);
// Narrowed to Right
strictEqual(value.right, 5);
import { strictEqual } from "node:assert/strict";
import { expectToBeFailure } from "@clipboard-health/testing-core";
import { failure, type ServiceResult, success } from "@clipboard-health/util-ts";
function validateAge(age: number): ServiceResult<number> {
if (age < 0) {
return failure({ issues: [{ code: "INVALID_AGE", message: "Age cannot be negative" }] });
}
return success(age);
}
const result = validateAge(-5);
expectToBeFailure(result);
// Narrowed to Left (Failure)
strictEqual(result.left.issues[0]?.message, "Age cannot be negative");
import { strictEqual } from "node:assert/strict";
import { expectToBeSuccess } from "@clipboard-health/testing-core";
import { failure, type ServiceResult, success } from "@clipboard-health/util-ts";
function validateAge(age: number): ServiceResult<number> {
if (age < 0) {
return failure({ issues: [{ code: "INVALID_AGE", message: "Age cannot be negative" }] });
}
return success(age);
}
const result = validateAge(25);
expectToBeSuccess(result);
// Narrowed to Right (Success)
strictEqual(result.right, 25);
import { strictEqual } from "node:assert/strict";
import { expectToBeDefined, expectToBeSafeParseError } from "@clipboard-health/testing-core";
import { z } from "zod";
const schema = z.object({ name: z.string() });
const value = schema.safeParse({ name: 1 });
expectToBeSafeParseError(value);
// Narrowed to `SafeParseError`
const firstIssue = value.error.issues[0];
expectToBeDefined(firstIssue);
// Narrowed to `ZodIssue`
strictEqual(firstIssue.message, "Expected string, received number");
import { strictEqual } from "node:assert/strict";
import { expectToBeSafeParseSuccess } from "@clipboard-health/testing-core";
import { z } from "zod";
const schema = z.object({ name: z.string() });
const value = schema.safeParse({ name: "hi" });
expectToBeSafeParseSuccess(value);
// Narrowed to `SafeParseSuccess`
strictEqual(value.data.name, "hi");
See package.json
scripts
for a list of commands.