Synchronous testing of async tasks.

gistfile1.txt

    func awaitWith<T>(
        testName: String = #function,
        file: StaticString = #file,
        line: UInt = #line,
        timeout: TimeInterval = 10,
        task: @escaping () async throws -> T
    ) throws -> T {
        var value: T?
        let handler: (T) -> Void = { value = $0 }
        let expectation = expectation(description: testName)
        Task.detached {
            let result = try await task()
            handler(result)
            expectation.fulfill()
        }

        wait(for: [expectation], timeout: timeout)

        return try XCTUnwrap(value, file: file, line: line)
    }

    func testRssUrl() throws {
        self.continueAfterFailure = false
        let xml = PodcastXml.url(url)
        let feed = try awaitWith { try await xml.feed }
        let rssFeed = feed.rssFeed
        XCTAssertNil(rssFeed)
        XCTAssertNotNil(rssFeed)
        validate(zebraFeed: try XCTUnwrap(rssFeed))
        validate(zebraFeed: rssFeed!)
    }