Add tests to HyperLink plugin

[ianeli1]

This test suite covers:

• Hovering over nothing displaying no title
• Hovering over a link displaying a message
• Ctrl+Clicking the link opening it in a new tab
• Clicking the link doing nothing

[JiuqingSong]

instead of really dispatch an event, we prefer to mock a PluginEvent and call plugin.onPluginEvent() directly since we don't really need to test browser's code, but just test our plugin code only.

[JiuqingSong]

Same for the others

[ianeli1]

this is handled by mouseover and mouseout events, not onPluginEvent

Should I (<any>plugin).onMouse and just test them directly?

roosterjs/packages/roosterjs-editor-plugins/lib/plugins/HyperLink/HyperLink.ts

Lines 46 to 66 in 64fd5e5

	this.disposer = editor.addDomEventHandler({
	mouseover: <DOMEventHandler>this.onMouse,
	mouseout: <DOMEventHandler>this.onMouse,
	blur: <DOMEventHandler>this.onBlur,
	});
	}
	protected onMouse = (e: MouseEvent) => {
	const a = this.editor?.getElementAtCursor(
	'a[href]',
	<Node>e.target
	) as HTMLAnchorElement | null;
	const href = a && this.tryGetHref(a);
	if (href) {
	this.editor?.setEditorDomAttribute(
	'title',
	e.type == 'mouseover' ? this.getTooltipCallback(href, a) : null
	);
	}
	};

[JiuqingSong]

@ianeli1 I think you can mock/spy editor.addDomEventHandler, so that you can easily get the onMouse callback in an elegant way.

[JiuqingSong]

Same for the others

[JiuqingSong]

this is nice