protractor端对端测试出现：Element not visible error (not able to click an element)

这在使用selenium自动测试中是一个相当常见的问题。
可能的原因以及解决办法有几种：
1.make sure the element you want to click is actually visible. Sometimes you need to make extra actions on a page to make the element visible. For example, open up a dropdown for an option to appear or open menu for submenu to appear
2.wait for the visibility of the element:

var EC = protractor.ExpectedConditions;
var mumbaiCity = element(by.id('mumbaiCity'));
browser.wait(EC.visibilityOf(mumbaiCity), 5000);
mumbaiCity.click();

3.there is an another element with the same id that is actually invisible. In this case, you need to improve your locator to match this specific element. For instance:

element(by.css(".city-checkbox #mumbaiCity")).click();
element(by.css(".city-checkbox input[ng-click*=Mumbai]")).click();

4.Or, if you got multiple elements matching the same locator - you can "filter" out a visible element:

var mumbaiCity = element.all(by.id('mumbaiCity')).filter(function (elm) {
    return elm.isDisplayed().then(function (isDisplayed) {
        return isDisplayed;
    });
}).first();
mumbaiCity.click();

5.move to element and then click via browser.actions():

var mumbaiCity = element(by.id('mumbaiCity'));
browser.actions().mouseMove(mumbaiCity).click().perform();

6.scroll into view of the element and then click:

var mumbaiCity = element(by.id('mumbaiCity'));
browser.executeScript("arguments[0].scrollIntoView();", mumbaiCity.getWebElement());
mumbaiCity.click();

7.click via javascript (beware of the differences though):

var mumbaiCity = element(by.id('mumbaiCity'));
browser.executeScript("arguments[0].click();", mumbaiCity.getWebElement());

8.sometimes, you just need to maximize the browser window:

browser.driver.manage().window().maximize();

参考自：stackoverflow