为什么在检查 textView 文本是否以预期字符串结尾（省略时）时 android espresso 测试失败

我有一个 android 测试，检查应用 android:ellipsize="end" 时外部文本消息是否被截断并以三个点结尾。我不知道为什么测试失败，尽管活动中呈现的文本格式正确。

@Test
fun when_errorMessage_is_very_long_then_text_of_errorMessageTextView_ends_with_dots() {

    //given
    val errorMessage = """
            Very long error, Very long error, Very long error, Very long error, Very long error,
            Very long error, Very long error, Very long error, Very long error, Very long error,
            Very long error, Very long error, Very long error, Very long error, Very long error,
            Very long error, Very long error, Very long error, Very long error, Very long 
    error,"""

    //when
    presentErrorActivityWith(errorMessage)

    //then
    onView(withId(R.id.errorMessageTextView)).check(matches(withText(endsWith("..."))));
}

我使用从导入的功能

import androidx.test.espresso.Espresso.onView
import androidx.test.espresso.assertion.ViewAssertions.matches
import androidx.test.espresso.matcher.ViewMatchers.withId
import androidx.test.espresso.matcher.ViewMatchers.withText
import androidx.test.ext.junit.runners.AndroidJUnit4

ErrorActivity 布局中的错误消息 TextView 声明

<TextView
    android:id="@+id/errorMessageTextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"

    android:ellipsize="end"
    android:maxLines="2"

    android:paddingLeft="24dp"
    android:paddingRight="24dp"

    android:layout_marginTop="8dp"

    android:layout_marginStart="40dp"
    android:layout_marginLeft="40dp"
    android:layout_marginEnd="40dp"
    android:layout_marginRight="40dp"
    app:layout_constraintTop_toBottomOf="@+id/errorMessageTitleTextView"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    android:text=""/>

要检查 TextView 的文本是否已省略，您可以创建自定义匹配器，如下所示：

fun ellipsized() = object : TypeSafeMatcher<View>() {
    override fun describeTo(description: Description) {
        description.appendText("with ellipsized text")
    }

    override fun matchesSafely(v: View): Boolean {
        if (!(v is TextView)) {
            return false
        }
        val textView: TextView = v
        val layout: Layout = textView.getLayout()
        val lines = layout.lineCount
        if (lines > 0) {
            val ellipsisCount = layout.getEllipsisCount(lines - 1)
            if (ellipsisCount > 0) {
                return true
            }
        }

        return false
    }
}

并这样称呼它：

onView(withId(R.id.errorMessageTextView))
    .check(matches(ellipsized()))