我正在使用 Specflow 和 Selenium 进行测试自动化，但是当我尝试执行测试时，我遇到了以下错误消息：

• 我的问题不是什么是NullReferenceException，而是将此参数'key'指向什么（和位置）作为异常的原因。

  

TearDown对于测试夹具MyProject.Features.MyFeature失败   System.ArgumentNullException：值不能为null。 （参数“键”）   TearDown：System.NullReferenceException：对象引用未设置为对象的实例。

并且：

  

错误消息：      OneTimeSetUp：System.ArgumentNullException：值不能为null。 （参数“键”）

这是我的情况：

Scenario: accessing the screen for the first time
    Given I accessed the screen for the first time
    Then the result grid should only show the phrase "Lorem ipsum"

这是我的StepDefinition.cs文件：

    [Binding]
    public class StepDefinition
    {
        PageObject pageObject = new PageObject();

        [Given(@"I accessed the screen for the first time")]
        public void GivenIaccessedTheScreenForTheFirstTime()
        {
            pageObject.NavigateToScreen();
        }

        [Then(@"the result grid should only show the phrase (.*)")]
        public void ThenTheResultGridShouldOnlyShowThePhrase(string phrase)
        {
            Assert.True(pageObject.isPhraseDisplayed(phrase));
        }        
    }

这是我的PageObject.cs文件：

        public PageObject() : base(){ } //I use a BasePageObject.cs file also

        public void NavigateToScreen()
        {
            driver.Navigate().GoToUrl(_urlHere_);
        }
        public bool isPhraseDisplayed(string phrase)
        {
            wait.Until(u => u.FindElement(_byIdOfWebElementHere_).Displayed);

            IWebElement element = driver.FindElement(_byIdOfWebElementHere_);
            return element.Displayed;
        }

这是BasePageObject.cs文件，它实现IDisposable接口：

        protected IWebDriver driver { get; set; }
        protected WebDriverWait wait { get; set; }

        public BasePageObject()
        {
            driver = new ChromeDriver();
        }

        [AfterScenario]
        public void Dispose()
        {
            driver.Close();
            driver.Quit();
            driver.Dispose();
        }
    }

异常堆栈跟踪：

Starting test execution,please wait...

A total of 1 test files matched the specified pattern.
TearDown failed for test fixture MyProject.Features.MyFeature
System.ArgumentNullException : Value cannot be null. (Parameter 'key')
TearDown : System.NullReferenceException : Object reference not set to an instance of an object.
   at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
   at System.Collections.Generic.Dictionary`2.TryGetvalue(TKey key,tvalue& value)
   at TechTalk.SpecFlow.Bindings.Discovery.RuntimeBindingRegistryBuilder.FindAttributeConstructorArg(ParameterInfo parameterInfo,Dictionary`2 namedAttributeValues)
   at TechTalk.SpecFlow.Bindings.Discovery.RuntimeBindingRegistryBuilder.<>c__DisplayClass8_0.<CreateAttribute>b__7(ParameterInfo p)
   at System.Linq.Enumerable.SelectArrayIterator`2.ToArray()
   at System.Linq.Enumerable.ToArray[tsource](IEnumerable`1 source)
   at TechTalk.SpecFlow.Bindings.Discovery.RuntimeBindingRegistryBuilder.CreateAttribute(Attribute attribute)
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.ToArray()
   at System.Linq.Enumerable.ToArray[tsource](IEnumerable`1 source)
   at TechTalk.SpecFlow.Bindings.Discovery.RuntimeBindingRegistryBuilder.Getattributes(IEnumerable`1 customAttributes)
   at TechTalk.SpecFlow.Bindings.Discovery.RuntimeBindingRegistryBuilder.CreateBindingSourceMethod(MethodInfo methodDefinition)
   at TechTalk.SpecFlow.Bindings.Discovery.RuntimeBindingRegistryBuilder.BuildBindingsFromType(Type type)
   at TechTalk.SpecFlow.Bindings.Discovery.RuntimeBindingRegistryBuilder.BuildBindingsFromAssembly(Assembly assembly)
   at TechTalk.SpecFlow.TestRunnerManager.BuildBindingRegistry(IEnumerable`1 bindingAssemblies)
   at TechTalk.SpecFlow.TestRunnerManager.InitializeBindingRegistry(ITestRunner testRunner)
   at TechTalk.SpecFlow.TestRunnerManager.CreateTestRunner(Int32 threadId)
   at TechTalk.SpecFlow.TestRunnerManager.GetTestRunnerWithoutExceptionHandling(Int32 threadId)
   at TechTalk.SpecFlow.TestRunnerManager.GetTestRunner(Int32 threadId)
   at TechTalk.SpecFlow.TestRunnerManager.GetTestRunner(Assembly testAssembly,Nullable`1 managedThreadId)
   at MyProject.Features.MyFeature.FeatureSetup()
--TearDown
   at MyProject.Features.MyFeature.FeatureTearDown()
  X AcessandoATelaDeConsultapelaPrimeiraVez [< 1ms]
  Error Message:
   OneTimeSetUp: System.ArgumentNullException : Value cannot be null. (Parameter 'key')

Results File: C:\Users\FAMG\AppData\Local\Temp\test-explorer-GvcYR7\0.trx

Total tests: 1
     Failed: 1
 Total time: 3,7733 Seconds

我认为重要的事情要指出：

• 我正在使用 VSCode ，而不是Visual Studio。
• 我在项目中安装的测试运行器是NUnit。