added Measure-Object tests. There are considerable differences between different versions of PowerShell

src/pester-tests/Measure-Object.Tests.ps1

@@ -0,0 +1,33 @@
+Describe "Measure-Object" {
+    $testObject = 1,3,4
+
+    It "Should be able to be called without error" {
+        { Measure-Object | Out-Null } | Should Not Throw
+    }
+
+    It "Should be able to call on piped input" {
+        { $testObject | Measure-Object } | Should Not Throw
+    }
+
+    It "Should be able to count the number of objects input to it" {
+        $($testObject | Measure-Object).Count | Should Be $testObject.Length
+    }
+
+    It "Should be able to count using the Property switch" {
+        $expected = $(Get-ChildItem).Length
+        $actual   = $(Get-ChildItem | Measure-Object -Property Length).Count
+        
+        $actual | Should Be $expected
+    }
+
+    It "Should be able to get additional stats" {
+        $actual = Get-Process | Measure-Object -Property workingset64 -Minimum -Maximum -Average
+
+        $actual.Average    | Should BeGreaterThan 0
+        $actual.Characters | Should BeNullOrEmpty
+        $actual.Lines      | Should BeNullOrEmpty
+        $actual.Maximum    | Should Not BeNullOrEmpty
+        $actual.Minimum    | Should Not BeNullOrEmpty
+        $actual.Sum        | Should BeNullOrEmpty
+    }
+}