Locator object cannot be null with Selenium PageObjects

Question

I'm sure this is a simple one but I have not been able to find the cause of this error let alone the solution.

I am using selenium page objects which has been running perfectly up until now when I have added a new page to my tests.

Here is my main code

class RunTest
{
   static IWebDriver driver;

   [Test]
   public void Login()
   {
      var options = new ChromeOptions();
      options.AddArguments("chrome.switches", "--disable-extensions --disable-extensions-file-access-check --disable-extensions-http-throttling --disable-infobars --enable-automation ");
      options.AddUserProfilePreference("credentials_enable_service", false);
      options.AddUserProfilePreference("profile.password_manager_enabled", false);
      driver = new ChromeDriver(options);

      driver.Url = ConfigurationManager.AppSettings["URL"];

      driver.Manage().Timeouts().ImplicitWait = TimeSpan.FromSeconds(10);

      var loginPage = new LoginPage(driver);
      loginPage.LoginToApplication("Test1");

      IWait<IWebDriver> wait = new WebDriverWait(driver, TimeSpan.FromSeconds(10));
      var element = wait.Until(ExpectedConditions.ElementIsVisible(By.XPath("//*[@id='content']/div/div/div/div/ul/li[4]/div[1]/div[2]/div/button[1]")));

      var setenv = new SetEnvironment(driver);
      setenv.SetEnvQA();
}

[Test]
public void AddBatchTest()
{
   var AddBatch = new Batch(driver);
   AddBatch.AddNewBatch("Test1");
}

[Test]
public void Test1()
{
   var NewCli = new AddNewClient(driver);
   NewCli.Addanewclient("Test1");
}

The Login and Test1 tests (Along with the others) run perfectly however the Batch test falls over with

System.ArgumentException : The SearchContext of the locator object cannot be null Parameter name: locator

The code in the batch class and AddNewClient class are identical so I cant see what the problem is

Batch:

namespace OnlineStore.PageObjects
{
    class Batch
    {
        IWebDriver driver;

        //Admin link in left hand otions
        [FindsBy(How = How.XPath, Using = "//*[@id='ctl00_NavigationPanel_navigationpanel1_hlAdmin']")]
        public IWebElement AdminScreen { get; set; }

        //Add new batch link
        [FindsBy(How = How.XPath, Using = "//*[@id='ctl00_MainBody_HyperLink38']")]
        public IWebElement AddNewBatchLnk { get; set; }

        [FindsBy(How = How.XPath, Using = "//*[@id='ctl00_MainBody_DatepickerReceived_txtDate']")]
        public IWebElement DateReceived { get; set; }

        [FindsBy(How = How.XPath, Using = "//*[@id='aspnetForm']/div[3]/div/div[2]/div[3]/table[3]/tbody/tr/td/table/tbody/tr[7]/td]")]
        public IWebElement SelectToday { get; set; }

        [FindsBy(How = How.XPath, Using = "//*[@id='ctl00_MainBody_txtTotal']")]
        public IWebElement BatchTotal { get; set; }

        [FindsBy(How = How.XPath, Using = "//*[@id='ctl00_MainBody_ucCurrency_ddlCurrency']")]
        public IWebElement Currency { get; set; }

        [FindsBy(How = How.XPath, Using = "//*[@id='ctl00_MainBody_cboAgency']")]
        public IWebElement Provider { get; set; }

        [FindsBy(How = How.XPath, Using = "//*[@id='ctl00_MainBody_txtNote']")]
        public IWebElement BatchNotes { get; set; }

        public Batch(IWebDriver driver)
        {
            this.driver = driver;
            PageFactory.InitElements(driver, this); 
        }

        public void AddNewBatch(string testName)
        {
            var userData = ExcelDataAccess.GetTestData(testName);

            IWait<IWebDriver> wait = new WebDriverWait(driver, TimeSpan.FromSeconds(30.00));

            AdminScreen.Click();
            wait.Until(ExpectedConditions.ElementIsVisible(By.XPath("//*[@id='ctl00_MainBody_HyperLink38']")));

            AddNewBatchLnk.Click();
            wait.Until(ExpectedConditions.ElementIsVisible(By.XPath("//*[@id='ctl00_MainBody_DatepickerReceived_txtDate']")));

            DateReceived.SendKeys("22/05/2017");
            //SelectToday.Click();
            BatchTotal.SendKeys("1000");
            Currency.SendKeys("USD");
            Provider.SendKeys("Client");
            BatchNotes.SendKeys("Some Batchg notes here please");

        }
    }
}

AddNewClient:

public AddNewClient(IWebDriver driver)
{
   this.driver = driver;
   PageFactory.InitElements(driver, this);
}

public void Addanewclient(string testName)
{ 
   //Code here
}

Any ideas?

Update: I tried moving the AddBatchTest code into the Login code script and it ran fine but when I pushed it back out to its own test it errored again.

Full stack trace as requested in the comments.

Result StackTrace:  
at OpenQA.Selenium.Support.PageObjects.PageFactory.InitElements(Object page, IElementLocator locator, IPageObjectMemberDecorator decorator)
   at OpenQA.Selenium.Support.PageObjects.PageFactory.InitElements(ISearchContext driver, Object page)
   at OnlineStore.PageObjects.Batch..ctor(IWebDriver driver) in C:\Users\andrew.logan-smith\documents\visual studio 2015\Projects\OnlineStore\OnlineStore\PageObjects\Batch.cs:line 54
   at OnlineStore.TestCases.RunTest.AddBatchTest() in C:\Users\andrew.logan-smith\documents\visual studio 2015\Projects\OnlineStore\OnlineStore\TestCases\RunTest.cs:line 52
Result Message: 
System.ArgumentException : The SearchContext of the locator object cannot be null
Parameter name: locator

Answer 1

The order of the Test methods in RunTest class is not necessarily the ecxution order. In your case the order is probably AddBatchTest() -> Login() -> Test1(). That cause the driver to be null when calling Batch constructor and PageFactory.InitElements receives null as the driver argument i.e. the SearchContext, hence the error

The SearchContext of the locator object cannot be null

InitElements method from github

public static void InitElements(ISearchContext driver, object page)
{
    InitElements(page, new DefaultElementLocator(driver));
}

I suggest you move the Login() under [SetUp] annotation and add [TearDown]. It will run before and after each test and provide you "clean slate"

public class RunTest
{
    private IWebDriver driver = null;

    [SetUp]
    public void Login()
    {
        driver = new ChromeDriver(options);
        //...
    }

    [Test]
    public void AddBatchTest()
    {
        var AddBatch = new Batch(driver);
        AddBatch.AddNewBatch("Test1");
    }

    [Test]
    public void Test1()
    {
        var NewCli = new AddNewClient(driver);
        NewCli.Addanewclient("Test1");
    }

    [TearDown]
    public void TearDown()
    {
        if (Driver != null)
        {
            Driver.Quit();
        }
    }
}

Edit

If you want to run SetUp and TearDown one time for all the tests you can use [TestFixtureSetUp] and [TestFixtureTearDown] annotations. You also need to add [TestFixture] to the class

[TestFixture]
public class RunTest
{
    [TestFixtureSetUp]
    public void SetUp()
    {
    }

    [Test]
    public void AddBatchTest()
    {
    }

    [Test]
    public void Test1()
    {
    }

    [TestFixtureTearDown]
    public void TearDown()
    {
    }
}

*This is for NUnit 2, for NUnit 3 use [OneTimeSetUp] and [OneTimeTearDown].