Namespace Test

Example

import { Test } from '@maddimathon/utility-typescript/types';
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Your type tests should probably be in the same place as your Javascript tests (and not where those objects are defined). (So replace this with your imported item(s) to test.)

declare function toTest( param: boolean ): boolean;
declare function toTest( param: string ): string;
declare function toTest( param: boolean | string ): boolean | string;
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These values should also be tested by Jest/etc. for their values, but this example is just looking at type testing.

const _tests_toTest = {
    bool: toTest( true ),
    string: toTest( 'string' ),
    either: toTest( 'unk' as boolean | string ),
};
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If any of these tests fail, the Expect type will cause an error.

// (export does nothing but avoid errors since these files don't go to prod!)
export type Test_toTest = [

    // testing the general return
    Test.Expect<Test.Exactly<ReturnType<typeof toTest>, boolean | string>>,

    // testing the override results
    Test.Expect<Test.Exactly<typeof _tests_toTest.bool, boolean>>,
    Test.Expect<Test.Exactly<typeof _tests_toTest.string, string>>,
    Test.Expect<Test.Exactly<typeof _tests_toTest.either, boolean | string>>,

    // testing what should fail is also useful
    Test.ExpectNot<Test.Exactly<typeof _tests_toTest.bool, string>>,
    Test.ExpectNot<Test.Exactly<typeof _tests_toTest.string, boolean>>,
    Test.ExpectNot<Test.Exactly<typeof _tests_toTest.either, any>>,
    Test.ExpectNot<Test.Exactly<typeof _tests_toTest.either, boolean>>,
    Test.ExpectNot<Test.Exactly<typeof _tests_toTest.either, string>>,
];
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