在 Kotlin 中测试私有方法

Question

如何在 Kotlin 中测试私有方法？我尝试从androidx.annotation.VisibleForTesting 添加@VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)，但它不会使我的函数私有

这就是我的使用方式

@VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
fun doSomething() {}

[编辑]

我知道我不应该测试 private 方法，但它现在总是微不足道的。下面的情况呢。

我有一个 CsvReader 类

class CsvReader(private val inputStream: InputStream, private val separator: String = "\t") {
    fun read(): List<String> {
        return read(inputStream.bufferedReader())
    }
    private fun read(bufferedReader: BufferedReader): List<String> {
        val line = bufferedReader.use { it.readLine() } // `use` is like try-with-resources in Java
        return parse(line)
    }
    private fun parse(line: String): List<String> {
        return line.split(separator)
    }
}

我为它写了测试

class CsvReaderTest {
    private val stream = mock<InputStream>()
    private val reader = CsvReader(stream)
    private val bufferedReader = mock<BufferedReader>()
    @Test
    fun read() {
        whenever(bufferedReader.readLine()).thenReturn("Jakub\tSzwiec")
        reader.read(bufferedReader) shouldEqual listOf("Jakub", "Szwiec")
    }
    @Test
    fun readWhenEmpty() {
        whenever(bufferedReader.readLine()).thenReturn("")
        reader.read(bufferedReader) shouldEqual listOf("")
    }
    @Test
    fun throwIOExceptionWhenReadingProblems() {
        whenever(bufferedReader.readLine()).thenThrow(IOException::class.java)
        val read = { reader.read(bufferedReader) }
        read shouldThrow IOException::class
    }
}

不幸的是，对于测试，我需要调用私有函数 fun read(bufferedReader: BufferedReader): List<String>，因为在模拟 File 时，file.bufferedReader 会给出 NullPointerException Unable to mock BufferedWriter class in junit

Answer 1

对此只有一个答案：不要尝试。

您编写源代码来传达意图。如果你做了一些private 的东西，那么这就是一个内部实现细节。它可能会在下一秒发生变化。

Answer 2

像这样：

fun callPrivate(objectInstance: Any, methodName: String, vararg args: Any?): Any? {
        val privateMethod: KFunction<*>? =
            objectInstance::class.functions.find { t -> return@find t.name == methodName }

        val argList = args.toMutableList()
        (argList as ArrayList).add(0, objectInstance)
        val argArr = argList.toArray()

        privateMethod?.apply {
            isAccessible = true
            return call(*argArr)
        }
            ?: throw NoSuchMethodException("Method $methodName does not exist in ${objectInstance::class.qualifiedName}")
        return null
    }

您需要传递要调用该方法的对象的实例、方法名称和所需参数

Answer 3

你可以使用java反射：

测试方法：

class ClassUnderTest {
      private fun printGreetings(name: String): String {
        return "Hello, $name"
      }
}

够了：

  private val classUnderTest = spyk(ClassUnderTest()) 

  @Test
    fun `should return greetings`() {
      val method = classUnderTest.javaClass.getDeclaredMethod("printGreetings", String::class.java)
      method.isAccessible = true
      val parameters = arrayOfNulls<Any>(1)
      parameters[0] = "Piotr"

      assertEquals("Hello, Piotr", method.invoke(classUnderTest, *parameters) )
  }