[test] Add getOrAwaitValue function in LiveDataTestUtil

Author: parkcheayeon

feature/stopdetail/src/test/java/com/chaeny/busoda/stopdetail/util/LiveDataTestUtil.kt

@@ -0,0 +1,33 @@
+package com.chaeny.busoda.stopdetail.util
+
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.Observer
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.TimeoutException
+
+fun <T> LiveData<T>.getOrAwaitValue(
+    time: Long = 2,
+    timeUnit: TimeUnit = TimeUnit.SECONDS,
+    afterObserve: () -> Unit = {}
+): T {
+    var data: T? = null
+    val latch = CountDownLatch(1)
+    val observer = object : Observer<T> {
+        override fun onChanged(value: T) {
+            data = value
+            latch.countDown()
+            this@getOrAwaitValue.removeObserver(this)
+        }
+    }
+    this.observeForever(observer)
+
+    afterObserve.invoke()
+
+    if (!latch.await(time, timeUnit)) {
+        this.removeObserver(observer)
+        throw TimeoutException("LiveData value was never set.")
+    }
+
+    @Suppress("UNCHECKED_CAST") return data as T
+}