4.7 KiB
title | bigimg | date | aliases | subtitle | categories | tags | |||||||
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Custom Webdriver Page Factories | Custom Webdriver Page Factories.jpg | 2014-09-22 |
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Wrapping WebElements to reduce boilerplate clutter |
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The problem: Webdriver elements returned by driver.FindElement()
are too generic. There're the Text
, SendKeys()
and Click()
methods/properties (depending your on C#/Java implementation). The solution is to simply wrap all elements inside custom HTML objects which contain specific methods like ShouldContainValue
or Type
(okay, that's a one-to-one mapping with SendKeys()
, but it's a lot less technical!). Instead of
[FindsBy(How = How.CssSelector, Using = ".ux-desktop-taskbar-startbutton")]
private IWebElement startButton;
[FindsBy(How = How.CssSelector, Using = ".other")]
private IWebElement whatever;
You'd find code like
[FindsBy(How = How.CssSelector, Using = ".ux-desktop-taskbar-startbutton")]
private HTMLSubmitButton startButton;
[FindsBy(How = How.CssSelector, Using = ".other")]
private HTMLInputBox whatever;
In java, this is not that difficult. Normally all fields annotated with FindsBy are filled in via reflection with PageFactory.InitElements()
. (warning: this creates proxies and does not yet actually do the lookup in the DOM tree. This is a good thing, as filling the fields usually happens inside the constructor of a page object.). initElements
returns the filled page, you can do a few things from there:
- postprocess the page and decorate your fields
- create your own page factory and create your own fields, wrapped around the webdriver proxies
In C#, you're in trouble - the class is sealed, and the proxy classes are internal. Creating your own factory is possible, but produces fuzzy code:
internal class PageFactory
{
private PageFactory()
{
}
private static By FindsByAttributeToBy(FindsByAttribute attribute)
{
return (By) typeof (FindsByAttribute).GetProperty("Finder", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(attribute);
}
public static void InitElements(IWebDriver driver, object page)
{
foreach (FieldInfo field in FindAllFieldsAndProperties(page.GetType()))
{
Attribute[] findsByAttribs = Attribute.GetCustomAttributes(field, typeof (FindsByAttribute), true);
if (findsByAttribs.Length > 0)
{
var findsByAttribute = (findsByAttribs[0] as FindsByAttribute);
if (field.FieldType == typeof (IWebElement))
{
field.SetValue(page, FindElement(driver, FindsByAttributeToBy(findsByAttribute)));
}
else if (typeof (IEnumerable).IsAssignableFrom(field.FieldType))
{
field.SetValue(page, FindElements(driver, FindsByAttributeToBy(findsByAttribute)));
}
}
}
}
private static IWebElement FindElement(IWebDriver driver, By by)
{
// warning: create WebProxyElement instead of directly doing a lookup
return driver.FindElement(by);
}
private static IReadOnlyCollection<IWebElement> FindElements(IWebDriver driver, By by)
{
// warning: create WebListProxyElement instead of directly doing a lookup
return driver.FindElements(by);
}
private static IEnumerable<FieldInfo> FindAllFieldsAndProperties(Type type)
{
var list = new List<FieldInfo>();
list.AddRange(type.GetFields(BindingFlags.Instance | BindingFlags.Public));
for (; type != (Type) null; type = type.BaseType)
{
list.AddRange(type.GetFields(BindingFlags.Instance | BindingFlags.NonPublic));
}
return list;
}
}
If you have a keen eye, you notice a few things:
- caching of the attribute wouldn't work anymore. The default C# WebDriver implementation is fuzzy and I didn't want to copypaste code I won't use.
- proxying won't work anymore, you'd have to use reflection to instantiate internal classes.
- reflection has been used to fetch the
By
instance of theFindsByAttribute
. Yay.
The above solution is too complex to solve a simple thing. Instead of a custom page factory, in C# we now use extension methods on IWebElement
. Another possibility would to create wrapper objects on-the-fly but you'd still have to map the "raw" web elements on page objects.