diff --git a/framework/default/modules/logger/services/logger/classes/tests/LoggerServiceTest.cls b/framework/default/modules/logger/services/logger/classes/tests/LoggerServiceTest.cls
new file mode 100644
index 00000000000..4da9a0318e4
--- /dev/null
+++ b/framework/default/modules/logger/services/logger/classes/tests/LoggerServiceTest.cls
@@ -0,0 +1,382 @@
+@isTest
+private without sharing class LoggerServiceTest
+{
+	@isTest
+	private static void log_whenGivenALevelAndAMessageAndLoggingIsEnabledForThatLevel_callsToLog() // NOPMD: Test method name format
+	{
+		LoggerService.Level level = LoggerService.Level.INFO;
+		String message = 'the message';
+
+		FakeLogger fakeLogger = new FakeLogger();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_INFO_Level_Messages__c = true );
+
+		Test.startTest();
+			LoggerService.log( level, message );
+		Test.stopTest();
+
+		System.assertEquals( 'log', fakeLogger.methods[0], 'log, when given a level and a message, and logging is enabled for that level, calls the service to log' );
+		System.assertEquals( new List<Object>{ level, message }, fakeLogger.parameters[0], 'log, when given a level and a message, and logging is enabled for that level, calls the service to log, passing parameters' );
+	}
+
+	@isTest
+	private static void log_whenGivenALevelAndAMessageAndLoggingIsDisabledForThatLevel_doesNotCallToLog() // NOPMD: Test method name format
+	{
+		LoggerService.Level level = LoggerService.Level.INFO;
+		String message = 'the message';
+
+		FakeLogger fakeLogger = new FakeLogger();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_INFO_Level_Messages__c = false );
+
+		Test.startTest();
+			LoggerService.log( level, message );
+		Test.stopTest();
+
+		System.assert( fakeLogger.methods.isEmpty(), 'log, when given a level and a message, and logging is disabled for that level, does not call against the service' );
+	}
+
+	@isTest
+	private static void log_whenGivenALevelAndAMessageAndLoggingAndNoConfig_asksServiceIfItShouldLog() // NOPMD: Test method name format
+	{
+		LoggerService.Level level = LoggerService.Level.INFO;
+		String message = 'the message';
+
+		FakeLogger fakeLogger = new FakeLogger().setDefaultLoggingEnabledReturns( true );
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c(); // nameless config means there's no config
+
+		Test.startTest();
+			LoggerService.log( level, message );
+		Test.stopTest();
+
+		System.assertEquals( 'getDefaultLoggingEnabled', fakeLogger.methods[0], 'log, when given a level and a message, and config is missing, asks the service if it should log' );
+		System.assertEquals( LoggerService.Level.INFO, fakeLogger.parameters[0][0], 'log, when given a level and a message, and config is missing, and config is missing, asks the service if it should log' );
+
+		System.assertEquals( 'log', fakeLogger.methods[1], 'log, when given a level and a message, and config is missing, asks the service if it should log, and calls the service if it should' );
+	}
+
+	@isTest
+	private static void log_whenGivenALevelAndAMessageAndLoggerThrowsException_doesNotThrow() // NOPMD: Test method name format
+	{
+		LoggerService.Level level = LoggerService.Level.INFO;
+		String message = 'the message';
+
+		FakeLogger fakeLogger = new FakeLogger().loggingThrowsException();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_INFO_Level_Messages__c = true );
+
+		Test.startTest();
+			LoggerService.log( level, message );
+		Test.stopTest();
+
+		System.assertEquals( 'log', fakeLogger.methods[0], 'log, when given a level and a message, and the logger throws an exception, does not throw' );
+	}
+
+	@isTest
+	private static void log_whenGivenALevelAndAMessageAndIdAndLoggingIsEnabledForThatLevel_callsToLog() // NOPMD: Test method name format
+	{
+		LoggerService.Level level = LoggerService.Level.WARN;
+		String message = 'the message';
+		Id relatedSobjectId = TestIdUtils.generateId( Contact.SobjectType );
+
+		FakeLogger fakeLogger = new FakeLogger();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_WARN_Level_Messages__c = true );
+
+		Test.startTest();
+			LoggerService.log( level, message, relatedSobjectId );
+		Test.stopTest();
+
+		System.assertEquals( 'log', fakeLogger.methods[0], 'log, when given a level and a message and sobject id, and logging is enabled for that level, calls the service to log' );
+		System.assertEquals( new List<Object>{ level, message, relatedSobjectId }, fakeLogger.parameters[0], 'log, when given a level and a message, and sobject id and logging is enabled for that level, calls the service to log, passing parameters' );
+	}
+
+	@isTest
+	private static void log_whenGivenALevelAndAMessageAndIdAndLoggingIsDisabledForThatLevel_doesNotCallToLog() // NOPMD: Test method name format
+	{
+		LoggerService.Level level = LoggerService.Level.WARN;
+		String message = 'the message';
+		Id relatedSobjectId = TestIdUtils.generateId( Contact.SobjectType );
+
+		FakeLogger fakeLogger = new FakeLogger();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_WARN_Level_Messages__c = false );
+
+		Test.startTest();
+			LoggerService.log( level, message, relatedSobjectId );
+		Test.stopTest();
+
+		System.assert( fakeLogger.methods.isEmpty(), 'log, when given a level and a message and sobject id, and logging is disabled for that level, does not call against the service' );
+	}
+
+	@isTest
+	private static void log_whenGivenALevelAndAMessageAndIdAndLoggingAndNoConfig_asksServiceIfItShouldLog() // NOPMD: Test method name format
+	{
+		LoggerService.Level level = LoggerService.Level.WARN;
+		String message = 'the message';
+		Id relatedSobjectId = TestIdUtils.generateId( Contact.SobjectType );
+
+		FakeLogger fakeLogger = new FakeLogger().setDefaultLoggingEnabledReturns( true );
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c(); // nameless config means there's no config
+
+		Test.startTest();
+			LoggerService.log( level, message, relatedSobjectId );
+		Test.stopTest();
+
+		System.assertEquals( 'getDefaultLoggingEnabled', fakeLogger.methods[0], 'log, when given a level and a message and sobject id, and config is missing, asks the service if it should log' );
+		System.assertEquals( LoggerService.Level.WARN, fakeLogger.parameters[0][0], 'log, when given a level and a message and sobject id, and config is missing, and config is missing, asks the service if it should log' );
+
+		System.assertEquals( 'log', fakeLogger.methods[1], 'log, when given a level and a message and sobject id, and config is missing, asks the service if it should log, and calls the service if it should' );
+	}
+
+	@isTest
+	private static void log_whenGivenALevelAndAMessageAndIdAndLoggerThrowsException_doesNotThrow() // NOPMD: Test method name format
+	{
+		LoggerService.Level level = LoggerService.Level.WARN;
+		String message = 'the message';
+		Id relatedSobjectId = TestIdUtils.generateId( Contact.SobjectType );
+
+		FakeLogger fakeLogger = new FakeLogger().loggingThrowsException();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_WARN_Level_Messages__c = true );
+
+		Test.startTest();
+			LoggerService.log( level, message, relatedSobjectId );
+		Test.stopTest();
+
+		System.assertEquals( 'log', fakeLogger.methods[0], 'log, when given a level and a message and sobject id, and the logger throws an exception, does not throw' );
+	}
+
+	@isTest
+	private static void log_whenGivenExceptionAndLoggingIsEnabledForThatLevel_callsToLog() // NOPMD: Test method name format
+	{
+		Exception exceptionToLog = new LocalException( 'message' );
+
+		FakeLogger fakeLogger = new FakeLogger();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_ERROR_Level_Messages__c = true );
+
+		Test.startTest();
+			LoggerService.log( exceptionToLog );
+		Test.stopTest();
+
+		System.assertEquals( 'log', fakeLogger.methods[0], 'log, when given an exception, and logging is enabled for that level, calls the service to log' );
+	}
+
+	@isTest
+	private static void log_whenGivenExceptionAndLoggingIsDisabledForErrors_doesNotCallToLog() // NOPMD: Test method name format
+	{
+		Exception exceptionToLog = new LocalException( 'message' );
+
+		FakeLogger fakeLogger = new FakeLogger();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_ERROR_Level_Messages__c = false );
+
+		Test.startTest();
+			LoggerService.log( exceptionToLog );
+		Test.stopTest();
+
+		System.assert( fakeLogger.methods.isEmpty(), 'log, when given an exception, and logging is disabled for errors, does not call against the service' );
+	}
+
+	@isTest
+	private static void log_whenGivenExceptionAndLoggingAndNoConfig_asksServiceIfItShouldLog() // NOPMD: Test method name format
+	{
+		Exception exceptionToLog = new LocalException( 'message' );
+
+		FakeLogger fakeLogger = new FakeLogger().setDefaultLoggingEnabledReturns( true );
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c(); // nameless config means there's no config
+
+		Test.startTest();
+			LoggerService.log( exceptionToLog );
+		Test.stopTest();
+
+		System.assertEquals( 'getDefaultLoggingEnabled', fakeLogger.methods[0], 'log, when given an exception, and config is missing, asks the service if it should log' );
+		System.assertEquals( LoggerService.Level.ERROR, fakeLogger.parameters[0][0], 'log, when given an exception, and config is missing, asks the service if it should log' );
+
+		System.assertEquals( 'log', fakeLogger.methods[1], 'log, when given an exception, and config is missing, asks the service if it should log, and calls the service if it should' );
+	}
+
+	@isTest
+	private static void log_whenGivenExceptionAndLoggerThrowsException_doesNotThrow() // NOPMD: Test method name format
+	{
+		Exception exceptionToLog = new LocalException( 'message' );
+
+		FakeLogger fakeLogger = new FakeLogger().loggingThrowsException();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_ERROR_Level_Messages__c = true );
+
+		Test.startTest();
+			LoggerService.log( exceptionToLog );
+		Test.stopTest();
+
+		System.assertEquals( 'log', fakeLogger.methods[0], 'log, when given an exception, and the logger throws an exception, does not throw' );
+	}
+
+	@isTest
+	private static void log_whenGivenExceptionAndIdAndLoggingIsEnabledForThatLevel_callsToLog() // NOPMD: Test method name format
+	{
+		Exception exceptionToLog = new LocalException( 'message' );
+		Id relatedSobjectId = TestIdUtils.generateId( Contact.SobjectType );
+
+		FakeLogger fakeLogger = new FakeLogger();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_ERROR_Level_Messages__c = true );
+
+		Test.startTest();
+			LoggerService.log( exceptionToLog, relatedSobjectId );
+		Test.stopTest();
+
+		System.assertEquals( 'log', fakeLogger.methods[0], 'log, when given an exception and an id, and logging is enabled for that level, calls the service to log' );
+	}
+
+	@isTest
+	private static void log_whenGivenExceptionAndIdAndLoggingIsDisabledForErrors_doesNotCallToLog() // NOPMD: Test method name format
+	{
+		Exception exceptionToLog = new LocalException( 'message' );
+		Id relatedSobjectId = TestIdUtils.generateId( Contact.SobjectType );
+
+		FakeLogger fakeLogger = new FakeLogger();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_ERROR_Level_Messages__c = false );
+
+		Test.startTest();
+			LoggerService.log( exceptionToLog, relatedSobjectId );
+		Test.stopTest();
+
+		System.assert( fakeLogger.methods.isEmpty(), 'log, when given an exception and an id, and logging is disabled for errors, does not call against the service' );
+	}
+
+	@isTest
+	private static void log_whenGivenExceptionAndIdAndLoggingAndNoConfig_asksServiceIfItShouldLog() // NOPMD: Test method name format
+	{
+		Exception exceptionToLog = new LocalException( 'message' );
+		Id relatedSobjectId = TestIdUtils.generateId( Contact.SobjectType );
+
+		FakeLogger fakeLogger = new FakeLogger().setDefaultLoggingEnabledReturns( true );
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c(); // nameless config means there's no config
+
+		Test.startTest();
+			LoggerService.log( exceptionToLog, relatedSobjectId );
+		Test.stopTest();
+
+		System.assertEquals( 'getDefaultLoggingEnabled', fakeLogger.methods[0], 'log, when given an exception and an id, and config is missing, asks the service if it should log' );
+		System.assertEquals( LoggerService.Level.ERROR, fakeLogger.parameters[0][0], 'log, when given an exception and an id, and config is missing, asks the service if it should log' );
+
+		System.assertEquals( 'log', fakeLogger.methods[1], 'log, when given an exception and an id, and config is missing, asks the service if it should log, and calls the service if it should' );
+	}
+
+	@isTest
+	private static void log_whenGivenExceptionAndIdAndLoggerThrowsException_doesNotThrow() // NOPMD: Test method name format
+	{
+		Exception exceptionToLog = new LocalException( 'message' );
+		Id relatedSobjectId = TestIdUtils.generateId( Contact.SobjectType );
+
+		FakeLogger fakeLogger = new FakeLogger().loggingThrowsException();
+		Application.SERVICE.setMock( ILoggerService.class, fakeLogger );
+
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_ERROR_Level_Messages__c = true );
+
+		Test.startTest();
+			LoggerService.log( exceptionToLog, relatedSobjectId );
+		Test.stopTest();
+
+		System.assertEquals( 'log', fakeLogger.methods[0], 'log, when given an exception and an id, and the logger throws an exception, does not throw' );
+	}
+
+	@isTest
+	private static void log_whenTheLoggerCannotBeFound_usesANullLogger() // NOPMD: Test method name format
+	{
+		Application.SERVICE.setMock( ILoggerService.class, null );
+		LoggerService.config = new Logging_Configuration__c( Name = 'Name', Log_INFO_Level_Messages__c = true );
+
+		Test.startTest();
+			LoggerService.log( LoggerService.Level.INFO, 'message' );
+		Test.stopTest();
+
+		System.assert( true, 'log, when the logger service implementation cannot be found, will use a null logger and no exception is thrown' );
+	}
+
+	class LocalException extends Exception {}
+	// This exists because StubProvider has difficulty creating a stub for ILoggerService
+	// Potentially it's a problem with overloaded methods defined in an interface.
+	class FakeLogger implements ILoggerService
+	{
+		public List<String> methods = new List<String>();
+		public List<List<Object>> parameters = new List<List<Object>>();
+		Boolean defaultLoggingEnabledReturns = false;
+		Boolean loggingThrowsException = false;
+
+		public FakeLogger loggingThrowsException()
+		{
+			loggingThrowsException = true;
+			return this;
+		}
+		public FakeLogger setDefaultLoggingEnabledReturns( Boolean returns )
+		{
+			defaultLoggingEnabledReturns = returns;
+			return this;
+		}
+		public Boolean getDefaultLoggingEnabled( LoggerService.Level logLevel )
+		{
+			methods.add( 'getDefaultLoggingEnabled' );
+			parameters.add( new List<Object>{ logLevel } );
+			return defaultLoggingEnabledReturns;
+		}
+		public void log( LoggerService.Level logLevel, String message )
+		{
+			methods.add( 'log' );
+			parameters.add( new List<Object>{ logLevel, message } );
+			if ( loggingThrowsException )
+			{
+				throw new LocalException( 'a message' );
+			}
+		}
+		public void log( LoggerService.Level logLevel, String message, Id relatedSobjectId )
+		{
+			methods.add( 'log' );
+			parameters.add( new List<Object>{ logLevel, message, relatedSobjectId } );
+			if ( loggingThrowsException )
+			{
+				throw new LocalException( 'a message' );
+			}
+		}
+		public void log( Exception exceptionToLog )
+		{
+			methods.add( 'log' );
+			parameters.add( new List<Object>{ exceptionToLog } );
+			if ( loggingThrowsException )
+			{
+				throw new LocalException( 'a message' );
+			}
+		}
+		public void log( Exception exceptionToLog, Id relatedSobject )
+		{
+			methods.add( 'log' );
+			parameters.add( new List<Object>{ exceptionToLog, relatedSobject });
+			if ( loggingThrowsException )
+			{
+				throw new LocalException( 'a message' );
+			}
+		}
+	}
+}
\ No newline at end of file
diff --git a/framework/default/modules/logger/services/logger/classes/tests/LoggerServiceTest.cls-meta.xml b/framework/default/modules/logger/services/logger/classes/tests/LoggerServiceTest.cls-meta.xml
new file mode 100644
index 00000000000..40d67933d00
--- /dev/null
+++ b/framework/default/modules/logger/services/logger/classes/tests/LoggerServiceTest.cls-meta.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ApexClass xmlns="http://soap.sforce.com/2006/04/metadata">
+    <apiVersion>54.0</apiVersion>
+    <status>Active</status>
+</ApexClass>