wip

src/functions/assert/Common/Collect-Input.ps1

@@ -1,8 +1,19 @@
 function Collect-Input ($ParameterInput, $PipelineInput, $IsInPipeline) {
     if ($IsInPipeline) {
-        $PipelineInput
+        # We are called like this: 1 | Assert-Equal -Expected 1, we will get $local:Input in $PipelineInput and $true in $IsInPipeline (coming from $MyInvocation.ExpectingInput).
+
+        if ($PipelineInput.Count -eq 0) {
+            # When calling @() | Assert-Equal -Expected 1, the engine will special case it, and we will get empty array $local:Input, fix that
+            # by returning empty array wrapped in array.
+            , @()
+        }
+        else {
+            # This is array of all the input, when we output it, the function will unwrap it. So we get the raw input on the output.
+            $PipelineInput
+        }
     }
     else {
-        $ParameterInput
+        # This is exactly what was provided to the ActualParmeter, wrap it in array so the function return can unwrap it.
+        , $ParameterInput
     }
 }

tst/functions/assert/Common/Collect-Input.Tests.ps1

@@ -0,0 +1,62 @@
+Set-StrictMode -Version Latest
+
+InPesterModuleScope {
+    Describe "Collect-Input" {
+        BeforeAll {
+            function Assert-PassThru {
+                # This is how all Assert-* functions look inside, here we just collect $Actual and return it.
+                [System.Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUseProcessBlockForPipelineCommand', '')]
+                param (
+                    [Parameter(ValueFromPipeline = $true)]
+                    $Actual
+                )
+
+
+                $Actual = Collect-Input -ParameterInput $Actual -PipelineInput $local:Input -IsInPipeline $MyInvocation.ExpectingInput
+
+                $Actual
+            }
+        }
+
+        It "Given `$null through pipeline it returns `$null" {
+            $in = $null | Assert-PassThru
+
+            Verify-True ($null -eq $in)
+        }
+
+        It "Given @() through pipeline it returns array with 0 items" {
+            $in = @() | Assert-PassThru
+
+            Verify-True ($in.GetType().Name -eq 'Object[]')
+            Verify-True ($in.Count -eq 0)
+        }
+
+        It "Given @() through pipeline it returns array with 0 items" {
+            $in = Assert-PassThru -Actual @()
+
+            Verify-True ($in.GetType().Name -eq 'Object[]')
+            Verify-True ($in.Count -eq 0)
+        }
+
+        It "Given @() through pipeline it returns array with 0 items" {
+            $in = Assert-PassThru -Actual $null
+
+            Verify-True ($in.GetType().Name -eq 'Object[]')
+            Verify-True ($in.Count -eq 0)
+        }
+
+        It "Given @() through pipeline it returns array with 0 items" {
+            $in = Assert-PassThru -Actual 1, 2
+
+            Verify-True ($in.GetType().Name -eq 'Object[]')
+            Verify-True ($in.Count -eq 0)
+        }
+
+        It "Given @() through pipeline it returns array with 0 items" {
+            $in = 1, 2 | Assert-PassThru
+
+            Verify-True ($in.GetType().Name -eq 'Object[]')
+            Verify-True ($in.Count -eq 0)
+        }
+    }
+}