Add test for wait for

src/test/kotlin/test/initialcapacity/streaming/waitfor/WaitForTest.kt

@@ -0,0 +1,42 @@
+package test.initialcapacity.streaming.waitfor
+
+import io.initialcapacity.streaming.waitfor.waitFor
+import kotlinx.coroutines.async
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.runBlocking
+import java.io.Writer
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class WaitForTest {
+    @Test
+    fun testWaitFor() = runBlocking {
+        val messages = Channel<String>()
+        val message = async { messages.receive() }
+        val writer = TestWriter()
+
+        writer.write("Start")
+        val waited = async { writer.write(writer.waitFor(message)) }
+
+        messages.send("End")
+        waited.await()
+        assertEquals(listOf("Start", "flush", "End"), writer.actions)
+    }
+}
+
+class TestWriter : Writer() {
+    val actions = mutableListOf<String>()
+
+    override fun close() {
+        actions.addLast("close")
+    }
+
+    override fun flush() {
+        actions.addLast("flush")
+    }
+
+    override fun write(cbuf: CharArray, off: Int, len: Int) {
+        actions.addLast(String(cbuf, off, len))
+    }
+}