(maint) Add a logging interface

Previously the logging object had no interface which made testing difficult.
This commit adds a new interface which new features can use, which makes mocking
the logging object possible.

Author: glennsarti

src/logging.ts

@@ -16,7 +16,19 @@ export enum LogLevel {
     Error,
 }
 
-export class Logger {
+/** Interface for logging operations. New features should use this interface for the "type" of logger.
+ *  This will allow for easy mocking of the logger during unit tests.
+ */
+export interface ILogger {
+    write(message: string, ...additionalMessages: string[]);
+    writeDiagnostic(message: string, ...additionalMessages: string[]);
+    writeVerbose(message: string, ...additionalMessages: string[]);
+    writeWarning(message: string, ...additionalMessages: string[]);
+    writeAndShowWarning(message: string, ...additionalMessages: string[]);
+    writeError(message: string, ...additionalMessages: string[]);
+}
+
+export class Logger implements ILogger {
 
     public logBasePath: string;
     public logSessionPath: string;

test/test_utils.ts

@@ -2,19 +2,9 @@
  * Copyright (C) Microsoft Corporation. All rights reserved.
  *--------------------------------------------------------*/
 
-import { Logger, LogLevel } from "../src/logging";
-
-export class MockLogger extends Logger {
-    // Note - This is not a true mock as the constructor is inherited and causes errors due to trying load
-    // the "PowerShell Extension Logs" multiple times.  Ideally logging should be via an interface and then
-    // we can mock correctly.
-
-    public dispose() { return undefined; }
-
-    public getLogFilePath(baseName: string): string { return "mock"; }
-
-    public writeAtLevel(logLevel: LogLevel, message: string, ...additionalMessages: string[]) { return undefined; }
+import { ILogger } from "../src/logging";
 
+export class MockLogger implements ILogger {
     public write(message: string, ...additionalMessages: string[]) { return undefined; }
 
     public writeDiagnostic(message: string, ...additionalMessages: string[]) { return undefined; }
@@ -28,6 +18,4 @@ export class MockLogger extends Logger {
     public writeError(message: string, ...additionalMessages: string[]) { return undefined; }
 
     public writeAndShowError(message: string, ...additionalMessages: string[]) { return undefined; }
-
-    public startNewLog(minimumLogLevel: string = "Normal") { return undefined; }
 }