KTOR-1045 Add MockEngine test for history iteration (#2431)

Author: e5l

ktor-client/ktor-client-mock/common/test/MockEngineTest.kt

@@ -0,0 +1,30 @@
+import io.ktor.client.*
+import io.ktor.client.engine.mock.*
+import io.ktor.client.request.*
+import io.ktor.http.*
+import kotlin.test.*
+
+/*
+ * Copyright 2014-2021 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+class MockEngineTest {
+    
+    @Test
+    fun testHistoryIteration() {
+        val client = HttpClient(MockEngine) {
+            engine {
+                addHandler {
+                    respond("Test")
+                }
+            }
+        }
+        val engine = client.engine as MockEngine
+        val count = engine.requestHistory
+            .map(HttpRequestData::url)
+            .map(Url::toString)
+            .count()
+
+        assertEquals(0, count)
+    }
+}