Improve PrintBackendServiceTestImpl usability

Move PrintBackendServiceTestImpl into its own files instead of being
bundled with PrintBackendBrowserTest.  This will enable it to be reused
by other forthcoming tests.

Add helper functions for launching the service.

Add ability to register a test service to be used in place of launching
out-of-process instances on-demand by regular production code.

This has no change to existing test coverage or behavior.

Bug: 809738
Change-Id: I74c596b3284e69d6eabd525eb77e5f6e8f8b0c05
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2631326Reviewed-by: Daniel Hosseinian <dhoss@chromium.org>
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Alan Screen <awscreen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846393}

chrome/browser/printing/DEPS

@@ -5,5 +5,6 @@ include_rules = [
 specific_include_rules = {
   "print_backend_browsertest.cc": [
     "+chrome/services/printing/print_backend_service_impl.h",
+    "+chrome/services/printing/print_backend_service_test_impl.h",
   ]
 }

chrome/browser/printing/print_backend_browsertest.cc

@@ -14,12 +14,12 @@
 #include "base/memory/scoped_refptr.h"
 #include "base/optional.h"
 #include "base/run_loop.h"
-#include "chrome/services/printing/print_backend_service_impl.h"
+#include "chrome/services/printing/print_backend_service_test_impl.h"
 #include "chrome/services/printing/public/mojom/print_backend_service.mojom.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "content/public/test/browser_test.h"
 #include "mojo/public/cpp/bindings/pending_receiver.h"
-#include "mojo/public/cpp/bindings/pending_remote.h"
+#include "mojo/public/cpp/bindings/remote.h"
 #include "printing/backend/print_backend.h"
 #include "printing/backend/test_print_backend.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -35,50 +35,20 @@ constexpr int32_t kCopiesMax = 123;
 
 }  // namespace
 
-// PrintBackendServiceTestImpl uses a TestPrintBackend to enable testing of the
-// PrintBackendService without relying upon the presence of real printer
-// drivers.
-class PrintBackendServiceTestImpl : public PrintBackendServiceImpl {
- public:
-  explicit PrintBackendServiceTestImpl(
-      mojo::PendingReceiver<mojom::PrintBackendService> receiver)
-      : PrintBackendServiceImpl(std::move(receiver)) {}
-  PrintBackendServiceTestImpl(const PrintBackendServiceTestImpl&) = delete;
-  PrintBackendServiceTestImpl& operator=(const PrintBackendServiceTestImpl&) =
-      delete;
-  ~PrintBackendServiceTestImpl() override = default;
-
-  // Overrides which need special handling for using `test_print_backend_`.
-  void Init(const std::string& locale) override {
-    test_print_backend_ = base::MakeRefCounted<TestPrintBackend>();
-    print_backend_ = test_print_backend_;
-  }
-
- private:
-  friend class PrintBackendBrowserTest;
-
-  scoped_refptr<TestPrintBackend> test_print_backend_;
-};
-
 class PrintBackendBrowserTest : public InProcessBrowserTest {
  public:
   PrintBackendBrowserTest() = default;
   ~PrintBackendBrowserTest() override = default;
 
-  void PreRunTestOnMainThread() override {
-    InProcessBrowserTest::PreRunTestOnMainThread();
-
-    // Launch the service, and bind the testing interface to it.
-    mojo::PendingReceiver<mojom::PrintBackendService> receiver =
-        mojo::PendingRemote<mojom::PrintBackendService>()
-            .InitWithNewPipeAndPassReceiver();
+  void LaunchUninitialized() {
     print_backend_service_ =
-        std::make_unique<PrintBackendServiceTestImpl>(std::move(receiver));
+        PrintBackendServiceTestImpl::LaunchUninitialized(remote_);
   }
 
   // Initialize and load the backend service with some test print drivers.
   void DoInitAndSetupTestData() {
-    print_backend_service_->Init(/*locale=*/"");
+    print_backend_service_ = PrintBackendServiceTestImpl::LaunchForTesting(
+        remote_, test_print_backend_);
 
     auto printer_info = std::make_unique<PrinterBasicInfo>(
         /*printer_name=*/kDefaultPrinterName,
@@ -91,7 +61,7 @@ class PrintBackendBrowserTest : public InProcessBrowserTest {
     // tests.
     auto default_caps = std::make_unique<PrinterSemanticCapsAndDefaults>();
     default_caps->copies_max = kCopiesMax;
-    print_backend_service_->test_print_backend_->AddValidPrinter(
+    test_print_backend_->AddValidPrinter(
         kDefaultPrinterName, std::move(default_caps), std::move(printer_info));
   }
 
@@ -155,6 +125,9 @@ class PrintBackendBrowserTest : public InProcessBrowserTest {
   bool received_message_ = false;
   base::OnceClosure quit_callback_;
 
+  mojo::Remote<mojom::PrintBackendService> remote_;
+  scoped_refptr<TestPrintBackend> test_print_backend_ =
+      base::MakeRefCounted<TestPrintBackend>();
   std::unique_ptr<PrintBackendServiceTestImpl> print_backend_service_;
 };
 
@@ -165,6 +138,9 @@ IN_PROC_BROWSER_TEST_F(PrintBackendBrowserTest, FailWithoutInit) {
   base::Optional<std::string> default_printer_name;
   base::Optional<PrinterSemanticCapsAndDefaults> printer_caps;
 
+  // Launch the service, but without initializing to desired locale.
+  LaunchUninitialized();
+
   // Safe to use base::Unretained(this) since waiting locally on the callback
   // forces a shorter lifetime than `this`.
   GetPrintBackendService()->GetDefaultPrinterName(

chrome/browser/printing/print_backend_service.cc

@@ -21,6 +21,10 @@ namespace {
 constexpr base::TimeDelta kResetOnIdleTimeout =
     base::TimeDelta::FromSeconds(20);
 
+// `PrintBackendService` override for testing.
+mojo::Remote<printing::mojom::PrintBackendService>*
+    g_print_backend_service_for_test = nullptr;
+
 }  // namespace
 
 const mojo::Remote<printing::mojom::PrintBackendService>&
@@ -29,6 +33,10 @@ GetPrintBackendService(const std::string& locale,
   static base::NoDestructor<base::flat_map<
       std::string, mojo::Remote<printing::mojom::PrintBackendService>>>
       remotes;
+
+  if (g_print_backend_service_for_test)
+    return *g_print_backend_service_for_test;
+
   std::string remote_id;
 #if defined(OS_WIN)
   // Windows drivers are not thread safe.  Use a process per driver to prevent
@@ -74,3 +82,8 @@ GetPrintBackendService(const std::string& locale,
 
   return service;
 }
+
+void SetPrintBackendServiceForTesting(
+    mojo::Remote<printing::mojom::PrintBackendService>* remote) {
+  g_print_backend_service_for_test = remote;
+}

chrome/browser/printing/print_backend_service.h

@@ -16,4 +16,9 @@ const mojo::Remote<printing::mojom::PrintBackendService>&
 GetPrintBackendService(const std::string& locale,
                        const std::string& printer_name);
 
+// Test support to override the print backend service for testing.  Caller
+// retains ownership of `remote`.
+void SetPrintBackendServiceForTesting(
+    mojo::Remote<printing::mojom::PrintBackendService>* remote);
+
 #endif  // CHROME_BROWSER_PRINTING_PRINT_BACKEND_SERVICE_H_

chrome/services/printing/DEPS

@@ -3,3 +3,9 @@ include_rules = [
   "+components/pwg_encoder",
   "+pdf/pdf.h",
 ]
+
+specific_include_rules = {
+  "print_backend_service_test_impl.cc": [
+    "+chrome/browser/printing/print_backend_service.h",
+  ]
+}

chrome/services/printing/print_backend_service_test_impl.cc

+// Copyright 2021 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/services/printing/print_backend_service_test_impl.h"
+
+#include <utility>
+
+#include "base/memory/scoped_refptr.h"
+#include "chrome/browser/printing/print_backend_service.h"
+#include "printing/backend/test_print_backend.h"
+
+namespace printing {
+
+PrintBackendServiceTestImpl::PrintBackendServiceTestImpl(
+    mojo::PendingReceiver<mojom::PrintBackendService> receiver)
+    : PrintBackendServiceImpl(std::move(receiver)) {}
+
+PrintBackendServiceTestImpl::~PrintBackendServiceTestImpl() = default;
+
+void PrintBackendServiceTestImpl::Init(const std::string& locale) {
+  DCHECK(test_print_backend_);
+  print_backend_ = test_print_backend_;
+}
+
+// static
+std::unique_ptr<PrintBackendServiceTestImpl>
+PrintBackendServiceTestImpl::LaunchUninitialized(
+    mojo::Remote<mojom::PrintBackendService>& remote) {
+  // Launch the service running locally in-process.
+  mojo::PendingReceiver<mojom::PrintBackendService> receiver =
+      remote.BindNewPipeAndPassReceiver();
+  return std::make_unique<PrintBackendServiceTestImpl>(std::move(receiver));
+}
+
+// static
+std::unique_ptr<PrintBackendServiceTestImpl>
+PrintBackendServiceTestImpl::LaunchForTesting(
+    mojo::Remote<mojom::PrintBackendService>& remote,
+    scoped_refptr<TestPrintBackend> backend) {
+  std::unique_ptr<PrintBackendServiceTestImpl> service =
+      LaunchUninitialized(remote);
+
+  // Do the common initialization using the testing print backend.
+  service->test_print_backend_ = backend;
+  service->Init(/*locale=*/std::string());
+
+  // Register this test version of print backend service to be used instead of
+  // launching instances out-of-process on-demand.
+  SetPrintBackendServiceForTesting(&remote);
+
+  return service;
+}
+
+}  // namespace printing

chrome/services/printing/print_backend_service_test_impl.h

+// Copyright 2021 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_SERVICES_PRINTING_PRINT_BACKEND_SERVICE_TEST_IMPL_H_
+#define CHROME_SERVICES_PRINTING_PRINT_BACKEND_SERVICE_TEST_IMPL_H_
+
+#include <memory>
+#include <string>
+
+#include "base/memory/scoped_refptr.h"
+#include "chrome/services/printing/print_backend_service_impl.h"
+#include "chrome/services/printing/public/mojom/print_backend_service.mojom.h"
+#include "mojo/public/cpp/bindings/pending_receiver.h"
+#include "mojo/public/cpp/bindings/remote.h"
+#include "printing/backend/test_print_backend.h"
+
+namespace printing {
+
+// `PrintBackendServiceTestImpl` uses a `TestPrintBackend` to enable testing
+// of the `PrintBackendService` without relying upon the presence of real
+// printer drivers.
+class PrintBackendServiceTestImpl : public PrintBackendServiceImpl {
+ public:
+  explicit PrintBackendServiceTestImpl(
+      mojo::PendingReceiver<mojom::PrintBackendService> receiver);
+  PrintBackendServiceTestImpl(const PrintBackendServiceTestImpl&) = delete;
+  PrintBackendServiceTestImpl& operator=(const PrintBackendServiceTestImpl&) =
+      delete;
+  ~PrintBackendServiceTestImpl() override;
+
+  // Overrides which need special handling for using `test_print_backend_`.
+  void Init(const std::string& locale) override;
+
+  // Launch the service in-process for testing using the provided backend.
+  static std::unique_ptr<PrintBackendServiceTestImpl> LaunchForTesting(
+      mojo::Remote<mojom::PrintBackendService>& remote,
+      scoped_refptr<TestPrintBackend> backend);
+
+ private:
+  friend class PrintBackendBrowserTest;
+
+  // Launch the service in-process for testing without initializing backend.
+  static std::unique_ptr<PrintBackendServiceTestImpl> LaunchUninitialized(
+      mojo::Remote<mojom::PrintBackendService>& remote);
+
+  scoped_refptr<TestPrintBackend> test_print_backend_;
+};
+
+}  // namespace printing
+
+#endif  // CHROME_SERVICES_PRINTING_PRINT_BACKEND_SERVICE_TEST_IMPL_H_

chrome/test/BUILD.gn

@@ -3087,7 +3087,11 @@ if (!is_android) {
     }
     if (enable_basic_printing &&
         (is_win || is_mac || is_linux || is_chromeos)) {
-      sources += [ "../browser/printing/print_backend_browsertest.cc" ]
+      sources += [
+        "../browser/printing/print_backend_browsertest.cc",
+        "../services/printing/print_backend_service_test_impl.cc",
+        "../services/printing/print_backend_service_test_impl.h",
+      ]
       deps += [
         "//chrome/services/printing:lib",
         "//printing:test_support",