Add test to check web vital scripts added

This test ensures that the embedded web vital scripts have been added
to the browser contexts internal evaluateOnNewDocumentSources slice.
It does not check whether this has then been applied to a page.

common/browser_context_test.go

@@ -0,0 +1,44 @@
+package common
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/grafana/xk6-browser/common/js"
+	"github.com/grafana/xk6-browser/k6ext"
+	"github.com/grafana/xk6-browser/k6ext/k6test"
+	"github.com/grafana/xk6-browser/log"
+)
+
+func TestNewBrowserContext(t *testing.T) {
+	t.Run("add_web_vital_js_scripts_to_context", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		logger := log.NewNullLogger()
+		b := newBrowser(ctx, cancel, nil, NewLaunchOptions(), logger)
+
+		vu := k6test.NewVU(t)
+		ctx = k6ext.WithVU(ctx, vu)
+
+		bc, err := NewBrowserContext(ctx, b, "some-id", nil, nil)
+		require.NoError(t, err)
+
+		webVitalIIFEScriptFound := false
+		webVitalInitScriptFound := false
+		for _, script := range bc.evaluateOnNewDocumentSources {
+			switch script {
+			case js.WebVitalIIFEScript:
+				webVitalIIFEScriptFound = true
+			case js.WebVitalInitScript:
+				webVitalInitScriptFound = true
+			default:
+				assert.Fail(t, "script is neither WebVitalIIFEScript nor WebVitalInitScript")
+			}
+		}
+
+		assert.True(t, webVitalIIFEScriptFound, "WebVitalIIFEScript was not initialized in the context")
+		assert.True(t, webVitalInitScriptFound, "WebVitalInitScript was not initialized in the context")
+	})
+}