Add ServiceClient tests for shared channels

Adds tests for support added in https://github.com/grpc/grpc-swift/pull/202 that allows `ServiceClient` instances to share a single `Channel`.

Tests/SwiftGRPCTests/BasicEchoTestCase.swift

@@ -32,21 +32,20 @@ extension Echo_EchoResponse {
 
 class BasicEchoTestCase: XCTestCase {
   func makeProvider() -> Echo_EchoProvider { return EchoProvider() }
-  
-  var defaultTimeout: TimeInterval { return 1.0 }
-  
+
   var provider: Echo_EchoProvider!
   var server: Echo_EchoServer!
   var client: Echo_EchoServiceClient!
   
+  var defaultTimeout: TimeInterval { return 1.0 }
   var secure: Bool { return false }
-  
+  var address: String { return "localhost:5050" }
+
   override func setUp() {
     super.setUp()
     
     provider = makeProvider()
     
-    let address = "localhost:5050"
     if secure {
       let certificateString = String(data: certificateForTests, encoding: .utf8)!
       server = Echo_EchoServer(address: address,

Tests/SwiftGRPCTests/ServiceClientTests.swift

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2018, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import Foundation
+@testable import SwiftGRPC
+import XCTest
+
+class ServiceClientTests: BasicEchoTestCase {
+  private lazy var sharedChannel = Channel(address: address, secure: false)
+
+  override func setUp() {
+    super.setUp()
+    sharedChannel = Channel(address: address, secure: false)
+  }
+
+  func testSharingChannelBetweenClientsUnaryAsync() {
+    let firstCallExpectation = expectation(description: "First call completes successfully")
+    let secondCallExpectation = expectation(description: "Second call completes successfully")
+
+    do {
+      let client1 = Echo_EchoServiceClient(channel: sharedChannel)
+      try _ = client1.get(Echo_EchoRequest(text: "foo")) { _, callResult in
+        XCTAssertEqual(.ok, callResult.statusCode)
+        firstCallExpectation.fulfill()
+      }
+
+      let client2 = Echo_EchoServiceClient(channel: sharedChannel)
+      try _ = client2.get(Echo_EchoRequest(text: "foo")) { _, callResult in
+        XCTAssertEqual(.ok, callResult.statusCode)
+        secondCallExpectation.fulfill()
+      }
+    } catch let error {
+      XCTFail(error.localizedDescription)
+    }
+
+    waitForExpectations(timeout: defaultTimeout)
+  }
+
+  func testSharedChannelStillWorksAfterFirstUnaryClientCompletes() {
+    do {
+      let client1 = Echo_EchoServiceClient(channel: sharedChannel)
+      let response1 = try client1.get(Echo_EchoRequest(text: "foo")).text
+      XCTAssertEqual("Swift echo get: foo", response1)
+    } catch let error {
+      XCTFail(error.localizedDescription)
+    }
+
+    do {
+      let client2 = Echo_EchoServiceClient(channel: sharedChannel)
+      let response2 = try client2.get(Echo_EchoRequest(text: "foo")).text
+      XCTAssertEqual("Swift echo get: foo", response2)
+    } catch let error {
+      XCTFail(error.localizedDescription)
+    }
+  }
+}