AssertJ的filteredOn方法在assertk中的等效实现是什么？

在assertk中，没有和AssertJ filteredOn完全对应的内置方法，但可以通过两种简洁的方式实现相同的列表过滤断言逻辑：

方式一：直接过滤列表后断言 #

利用Kotlin标准库的filter函数先筛选出目标元素，再对过滤结果执行断言：

@Test
fun `filtered assertion in assertk`() {
    val amenities = listOf(
        Amenity(name = "Camping", selected = true),
        Amenity(name = "Hiking", selected = false),
        Amenity(name = "Swimming", selected = false)
    )

    assertThat(amenities.filter { it.selected })
        .containsExactly(Amenity(name = "Camping", selected = true))
}

data class Amenity(
    val name: String,
    val selected: Boolean
)

方式二：使用transform在断言链中完成过滤 #

如果希望保持断言链的连贯性，可以用assertk的transform方法，在断言流程中嵌入过滤逻辑，还能添加自定义描述提升失败信息的可读性：

@Test
fun `filtered assertion with transform`() {
    val amenities = listOf(
        Amenity(name = "Camping", selected = true),
        Amenity(name = "Hiking", selected = false),
        Amenity(name = "Swimming", selected = false)
    )

    assertThat(amenities)
        .transform("selected amenities") { it.filter { amenity -> amenity.selected } }
        .containsExactly(Amenity(name = "Camping", selected = true))
}

两种方式都能实现和AssertJ filteredOn完全一致的效果，具体选择可以根据代码风格和可读性需求决定。

内容的提问来源于stack exchange，提问作者Ryan Payne