Fix event firing

src/TestUtils.test.ts

@@ -432,7 +432,7 @@ export class MockCompositionHelper implements ICompositionHelper {
 
 export class MockCharSizeService implements ICharSizeService {
   get hasValidSize(): boolean { return this.width > 0 && this.height > 0; }
-  onCharSizeChange: IEvent<string>;
+  onCharSizeChange: IEvent<void>;
   constructor(public width: number, public height: number) {}
   measure(): void {}
 }