assertThat(
            commonPrefixOf(listOf(a, b)),
            equalTo(listOf("a", "b", "c"))
        )
    }

    @Test
    fun `empty lists have empty prefix`() {

        assertThat(
            commonPrefixOf(emptyList()),
            equalTo(emptyList<Any>())
        )
        assertThat(
            commonPrefixOf(listOf(emptyList())),
            equalTo(emptyList<Any>())