feat(test): dummy writers and readers

src/test/kotlin/bridge/DummyReader.kt

@@ -0,0 +1,25 @@
+package bridge
+
+class DummyReader(private val contents: Array<ByteArray>) : Reader {
+  private var index = 0
+
+  override suspend fun read(): Reader.Result {
+    return readSync()
+  }
+
+  override fun readSync(): Reader.Result {
+    // If we have read all the contents, return closed.
+    if (isClosed()) {
+      return Reader.Result.closed()
+    }
+
+    // Increment the index and return the next value.
+    val value = contents[index]
+    index += 1
+    return Reader.Result.success(value)
+  }
+
+  override fun isClosed(): Boolean {
+    return index >= contents.size
+  }
+}

src/test/kotlin/bridge/DummyWriter.kt

@@ -0,0 +1,25 @@
+package bridge
+
+class DummyWriter : Writer {
+  private val values = mutableListOf<ByteArray>()
+  private var closed = false
+
+  override suspend fun push(value: ByteArray) {
+    pushSync(value)
+  }
+
+  override fun pushSync(value: ByteArray) {
+    if (closed) {
+      throw IllegalStateException("Cannot push to closed writer.")
+    }
+    values.add(value)
+  }
+
+  override fun close() {
+    closed = true
+  }
+
+  fun getValues(): List<ByteArray> {
+    return values
+  }
+}