Added Get-EventSubscriber pester test

src/pester-tests/Get-EventSubscriber.Tests.ps1

@@ -0,0 +1,30 @@
+Describe "Get-EventSubscriber" {
+   
+        AfterEach {
+            Unregister-Event -SourceIdentifier PesterTestRegister -ErrorAction SilentlyContinue
+        }
+
+    Context "Check return type of Get-EventSubscriber" {
+	
+        It "Should return System.Management.Automation.PSEventSubscriber as return type of New-Event" {
+	    $pesterobject = (New-Object System.Collections.ObjectModel.ObservableCollection[object])
+	    Register-ObjectEvent -InputObject $pesterobject -EventName CollectionChanged -SourceIdentifier PesterTestRegister
+	    (Get-EventSubscriber).GetType() | Should Be System.Management.Automation.PSEventSubscriber
+	}
+    }
+
+    Context "Check Get-EventSubscriber can validly register events"{
+	It "Should return source identifier of PesterTimer " {
+	    $pesterobject = (New-Object System.Collections.ObjectModel.ObservableCollection[object])
+	    Register-ObjectEvent -InputObject $pesterobject -EventName CollectionChanged -SourceIdentifier PesterTestRegister
+	    (Get-EventSubscriber -SourceIdentifier PesterTestRegister).SourceIdentifier | Should Be "PesterTestRegister"
+	}
+
+        It "Should return an integer greater than 0 for the SubscriptionId" {
+            $pesterobject = (New-Object System.Collections.ObjectModel.ObservableCollection[object])
+	    Register-ObjectEvent -InputObject $pesterobject -EventName CollectionChanged -SourceIdentifier PesterTestRegister
+	    (Get-EventSubscriber -SourceIdentifier PesterTestRegister).SubscriptionId | Should BeGreaterThan 0
+
+	}
+    }
+}