test_doubles__mocks.kt

@Test fun `every visited URL gets saved to the browser's history`() {
    val mockHistory = MockHistory()
    val browser = Browser(mockHistory)

    browser.visit(URL("https://www.le0nidas.gr"))

    mockHistory.verifySavedUrlIs(expectedURL = URL("https://www.le0nidas.gr"))
}
    
private class MockHistory : History {

    private var savedURL: URL? = null

    override fun push(url: URL) {
        savedURL = url
    }

    override fun pop(): URL {
        TODO("Not yet implemented")
    }

    override fun peek(): URL {
        TODO("Not yet implemented")
    }

    fun verifySavedUrlIs(expectedURL: URL) {
        assertThat(savedURL, equalTo(expectedURL))
    }
}