import XCTest


@available(iOS 9.0, OSX 10.11, *)

extension XCUIElement {

    public var isVisible: Bool {
        return exists && !frame.isEmpty && XCUIApplication().windows.element(boundBy: 0).frame.contains(frame)
    }

}

import XCTest


@available(iOS 9.0, OSX 10.11, *)

public extension XCUIElement {

    var isVisible: Bool {
        return exists && !frame.isEmpty && XCUIApplication().windows.element(boundBy: 0).frame.contains(frame)
    }

}

--- 
+++ 
@@ -3,9 +3,9 @@
 
 @available(iOS 9.0, OSX 10.11, *)
 
-public extension XCUIElement {
+extension XCUIElement {
 
-    var isVisible: Bool {
+    public var isVisible: Bool {
         return exists && !frame.isEmpty && XCUIApplication().windows.element(boundBy: 0).frame.contains(frame)
     }
 
Make public variable instead of extension
