network_context: Add fake network context

Introduce the fake network context class, used by unit tests, to avoid
duplication across multiple routines.

BUG=chromium:956783
TEST=none

Change-Id: I536a208c32a6454c832847325eb3d933d357b40c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2434092Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Kartik Hegde <khegde@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812443}

chrome/browser/chromeos/BUILD.gn

@@ -3419,6 +3419,8 @@ source_set("unit_tests") {
     "net/network_diagnostics/dns_resolver_present_routine_unittest.cc",
     "net/network_diagnostics/fake_host_resolver.cc",
     "net/network_diagnostics/fake_host_resolver.h",
+    "net/network_diagnostics/fake_network_context.cc",
+    "net/network_diagnostics/fake_network_context.h",
     "net/network_diagnostics/gateway_can_be_pinged_routine_unittest.cc",
     "net/network_diagnostics/has_secure_wifi_connection_routine_unittest.cc",
     "net/network_diagnostics/http_firewall_routine_unittest.cc",

chrome/browser/chromeos/net/network_diagnostics/fake_network_context.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/chromeos/net/network_diagnostics/fake_network_context.h"
+
+#include <utility>
+
+namespace chromeos {
+namespace network_diagnostics {
+
+FakeNetworkContext::FakeNetworkContext() = default;
+
+FakeNetworkContext::~FakeNetworkContext() = default;
+
+void FakeNetworkContext::CreateHostResolver(
+    const base::Optional<net::DnsConfigOverrides>& config_overrides,
+    mojo::PendingReceiver<network::mojom::HostResolver> receiver) {
+  DCHECK(!resolver_);
+  resolver_ = std::make_unique<FakeHostResolver>(std::move(receiver));
+  resolver_->set_fake_dns_results(std::move(fake_dns_results_));
+}
+
+}  // namespace network_diagnostics
+}  // namespace chromeos

chrome/browser/chromeos/net/network_diagnostics/fake_network_context.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_CHROMEOS_NET_NETWORK_DIAGNOSTICS_FAKE_NETWORK_CONTEXT_H_
+#define CHROME_BROWSER_CHROMEOS_NET_NETWORK_DIAGNOSTICS_FAKE_NETWORK_CONTEXT_H_
+
+#include <deque>
+#include <memory>
+
+#include "chrome/browser/chromeos/net/network_diagnostics/fake_host_resolver.h"
+#include "services/network/test/test_network_context.h"
+
+namespace chromeos {
+namespace network_diagnostics {
+
+// Used in unit tests, the FakeNetworkContext class simulates the behavior of a
+// network context.
+class FakeNetworkContext : public network::TestNetworkContext {
+ public:
+  FakeNetworkContext();
+  ~FakeNetworkContext() override;
+
+  // network::TestNetworkContext:
+  void CreateHostResolver(
+      const base::Optional<net::DnsConfigOverrides>& config_overrides,
+      mojo::PendingReceiver<network::mojom::HostResolver> receiver) override;
+
+  // Sets the fake dns results.
+  void set_fake_dns_results(
+      std::deque<FakeHostResolver::DnsResult*> fake_dns_results) {
+    fake_dns_results_ = std::move(fake_dns_results);
+  }
+
+ private:
+  std::unique_ptr<FakeHostResolver> resolver_;
+  std::deque<FakeHostResolver::DnsResult*> fake_dns_results_;
+};
+
+}  // namespace network_diagnostics
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_NET_NETWORK_DIAGNOSTICS_FAKE_NETWORK_CONTEXT_H_