Add a basic test for the logger writer

PiperOrigin-RevId: 764774015

internal/platform/BUILD

@@ -28,6 +28,7 @@ cc_library(
         "@com_google_absl//absl/log",
         "@com_google_absl//absl/log:check",
         "@com_google_absl//absl/log:globals",
+        "@com_google_absl//absl/log:log_sink_registry",
     ],
 )
 
@@ -287,6 +288,7 @@ cc_library(
         "@com_google_absl//absl/log",
         "@com_google_absl//absl/log:check",
         "@com_google_absl//absl/log:globals",
+        "@com_google_absl//absl/log:log_sink_registry",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/synchronization",
         "@com_google_absl//absl/time",

internal/platform/implementation/apple/Tests/BUILD

@@ -70,11 +70,27 @@ objc_library(
     ],
 )
 
+objc_library(
+    name = "LoggerWriterTestslib",
+    testonly = True,
+    srcs = [
+        "nearby_logger_writer_test.mm",
+    ],
+    deps = [
+        "//internal/platform:logging",
+        "//internal/platform/implementation/apple:logger_writer",
+        "//third_party/apple_frameworks:Foundation",
+        "//third_party/apple_frameworks:XCTest",
+        "//third_party/objective_c/google_toolbox_for_mac:GTM_Logger",
+    ],
+)
+
 ios_unit_test(
     name = "PlatformTests",
     minimum_os_version = IOS_MINIMUM_OS,
     runner = IOS_LATEST_TEST_RUNNER,
     deps = [
+        ":LoggerWriterTestslib",
         ":PlatformTestslib",
     ],
 )

internal/platform/implementation/apple/Tests/nearby_logger_writer_test.mm

@@ -0,0 +1,81 @@
+// Copyright 2025 Google LLC
+//
+// 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
+//
+//     https://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 <XCTest/XCTest.h>
+#import "GoogleToolboxForMac/GTMLogger.h"
+
+#include "internal/platform/implementation/apple/nearby_logger_writer.h"
+
+#include <string>
+#include <utility>
+
+#include "internal/platform/logging.h"
+
+class AbslFileLogSink : public absl::LogSink {
+ public:
+  AbslFileLogSink() = default;
+  ~AbslFileLogSink() override = default;
+  void Send(const absl::LogEntry& entry) override {
+    logMessage_ = std::string(entry.text_message());
+    severity_ = entry.log_severity();
+  }
+
+  std::string GetLogMessage() const { return logMessage_; }
+  absl::LogSeverity GetSeverity() const { return severity_; }
+
+ private:
+  std::string logMessage_;
+  absl::LogSeverity severity_ = absl::LogSeverity::kInfo;
+};
+
+@interface NearbyLoggerWriterTest : XCTestCase
+@end
+
+@implementation NearbyLoggerWriterTest {
+  std::unique_ptr<AbslFileLogSink> _logSink;
+}
+
+- (void)setUp {
+  [super setUp];
+  _logSink = std::make_unique<AbslFileLogSink>();
+  absl::SetGlobalVLogLevel(1);
+  absl::AddLogSink(_logSink.get());
+  nearby::apple::EnableNearbyLoggerWriter();
+}
+
+- (void)tearDown {
+  absl::RemoveLogSink(_logSink.get());
+  _logSink.reset();
+  [super tearDown];
+}
+
+- (void)testInfoLogMessage {
+  GTMLoggerInfo(@"Hello, world!");
+  XCTAssertEqual(_logSink->GetLogMessage(), "Hello, world!");
+  XCTAssertEqual(_logSink->GetSeverity(), absl::LogSeverity::kInfo);
+}
+
+- (void)testErrorLogMessage {
+  GTMLoggerError(@"Error!");
+  XCTAssertEqual(_logSink->GetLogMessage(), "Error!");
+  XCTAssertEqual(_logSink->GetSeverity(), absl::LogSeverity::kError);
+}
+
+- (void)testVerboseLogMessage {
+  GTMLoggerDebug(@"Verbose!");
+  XCTAssertEqual(_logSink->GetLogMessage(), "Verbose!");
+  XCTAssertEqual(_logSink->GetSeverity(), absl::LogSeverity::kInfo);
+}
+
+@end

internal/platform/logging.h

@@ -20,13 +20,14 @@
 #include "base/check.h"
 #include "base/check_op.h"
 #include "base/logging.h"
-#else                                    // defined(NEARBY_CHROMIUM)
+#else                                                // defined(NEARBY_CHROMIUM)
 // IWYU pragma: begin_exports
-#include "absl/log/check.h"  // nogncheck
-#include "absl/log/globals.h"  // nogncheck
-#include "absl/log/log.h"    // nogncheck
+#include "absl/log/check.h"              // nogncheck
+#include "absl/log/globals.h"            // nogncheck
+#include "absl/log/log.h"                // nogncheck
+#include "absl/log/log_sink_registry.h"  // nogncheck
 // IWYU pragma: end_exports
-#endif                                   // defined(NEARBY_CHROMIUM)
+#endif                                               // defined(NEARBY_CHROMIUM)
 
 // Public APIs
 // The stream statement must come last, or it won't compile.