Add a test for WaitForLoadState networkidle

This test will ensure that when WaitForLoadState with waituntil
networkidle is called, that it doesn't block for the lifecycle event
if that event has already fired, and so uses the frame's internal
state to unblock quickly.

Author: ankur22

tests/lifecycle_wait_test.go

@@ -124,6 +124,56 @@ func TestLifecycleWaitForLoadStateDOMContentLoaded(t *testing.T) {
 	})
 }
 
+func TestLifecycleWaitForLoadStateNetworkIdle(t *testing.T) {
+	// Test description
+	//
+	// 1. goto /home and wait for the networkidle lifecycle event.
+	// 2. use WaitForLoadState with networkidle to ensure that
+	//    networkidle lifecycle event has already fired.
+	//
+	// Success criteria: We wait for all network requests and async
+	//                   scripts to complete. We also want to ensure
+	//                   that the networkidle event is stored internally,
+	//                   and we don't block on WaitForLoadState.
+
+	t.Parallel()
+
+	tb := newTestBrowser(t, withFileServer())
+	p := tb.NewPage(nil)
+	tb.withHandler("/home", func(w http.ResponseWriter, r *http.Request) {
+		http.Redirect(w, r, tb.staticURL("wait_for_nav_lifecycle.html"), http.StatusMovedPermanently)
+	})
+
+	var counter int64
+	var counterMu sync.Mutex
+	tb.withHandler("/ping", func(w http.ResponseWriter, _ *http.Request) {
+		counterMu.Lock()
+		defer counterMu.Unlock()
+
+		counter++
+		fmt.Fprintf(w, "pong %d", counter)
+	})
+
+	tb.withHandler("/ping.js", func(w http.ResponseWriter, _ *http.Request) {
+		fmt.Fprintf(w, `
+				var pingJSTextOutput = document.getElementById("pingJSText");
+				pingJSTextOutput.innerText = "ping.js loaded from server";
+			`)
+	})
+
+	waitUntil := common.LifecycleEventNetworkIdle
+	assertHome(t, tb, p, waitUntil, func() {
+		result := p.TextContent("#pingRequestText", nil)
+		assert.EqualValues(t, "Waiting... pong 10 - for loop complete", result)
+
+		result = p.TextContent("#pingJSText", nil)
+		assert.EqualValues(t, "ping.js loaded from server", result)
+
+		// This shouldn't block and return after calling hasLifecycleEventFired.
+		p.WaitForLoadState(waitUntil.String(), nil)
+	})
+}
+
 func TestLifecycleReloadLoad(t *testing.T) {
 	t.Parallel()