期望在 Android Espresso 测试中出现异常 - 失败

Question

I am writing tests in Espresso for my Android application using Kotlin. I want to expect an exception as in the unit test and pass the test if such an exception is found.

I had a test that was checking for the Intent extras format. In the implementation I have thrown an exception after getting an incorrect value in the intent. I want to pass the test is this exception is thrown. Running the test results with a "Test failed" and java.lang.IllegalArgumentException which is the same as I am trying to catch.

I tried with this annotation at first:

@Test(expected = IllegalArgumentException::class)

Then I tried with a org.jetbrains.kotlin:kotlin-test dependency and the following assertion:

assertFailsWith<java.lang.IllegalArgumentException> {
    val activityIntent = Intent()
    activityIntent.putExtra("extra_connection_number", intentExtraConnectionNumber)
    activityRule.launchActivity(activityIntent)
}

What may be also important is that the exception is thrown in the onCreateView starting as so:

@Throws(java.lang.IllegalArgumentException::class)
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
    val layout = inflater.inflate(R.layout.configuration_fragment, container, false)
    var connectionNumber: Int? =
        activity!!.intent.getIntExtra(resources.getString(R.string.extra_connection_number), -1)
    if (connectionNumber == -1) {
        throw IllegalArgumentException()
    }
(...)

The intent is created with the given extra, and it is failing in a place I wanted it to fail. But the thrown exception is not caught by the Espresso. Why? What am I missing?

I am aware it may be incompatible with Espresso, but I cannot find a right documentation helping me with the problem.

Answer 1

Use normal try catch solved my problem, i know the exception is nested. But we can still check it by cause:

var error: Throwable? = null
try {
    onView(something).perform(click())
} catch (e: Throwable) {
    error = e;
}
assert(error!!.cause is MySpecificException)
assert(error!!.cause!!.message == "My specific error message")

I have tried another approach , but i ended up with flaky tests result.