tyte
Write Jest tests for TypeScript types.
Usage
Also see Caveats section below
export type MyNumber = number;
export type MyFunction = (input: string) => boolean;Positive testing:
test("MyNumber should resolve to a number", tyte((value: MyNumber) => {
tyte.expectType<number>(value);
}));
describe("MyFunction", () => {
it("should take a string input", tyte((subject: MyFunction) => {
tyte.fn.expectParams<[string]>(subject);
}));
it("should return a boolean", tyte((subject: MyFunction) => {
tyte.fn.expectReturns<boolean>(subject);
}));
});Negative testing:
test("MyNumber should not resolve to a string", tyte((value: MyNumber) => {
// @ts-expect-error
tyte.expectType<string>(value);
}));Use several subjects in test callback:
test("MyNumber should resolve to a number", tyte((
value: MyNumber,
values: MyNumber[],
) => {
tyte.expectType<number>(value);
tyte.expectType<number[]>(values);
}));
Iterate over several subjects in .each methods:
type Forward = "forward";
type Vertical = "up" | "down" | Forward;
type Horizontal = "left" | "right" | Forward;
test.each([
[ "Vertical", tyte.subject as Vertical & Forward ],
[ "Horizontal", tyte.subject as Horizontal & Forward ],
])("%s should include 'forward'", (identifier, subject) => {
tyte.expectType<"forward">(subject);
});Caveats
-
Currently, it is not possible to use
tyte()as a function in.eachmethods, as in:test.each(list)("should ...", tyte((element) => { // ... }));
Such code will produce compilation errors.
Any suggestions and PRs are very welcome!