[macOS] Pester tests invocation after install. (#2421)

* [macOS] Fail Pester tests on error

* return it back

* [macOS] Pester tests invokation after install

* fix nitpicks

* CocoaPods fix

images/macos/tests/PHP.Tests.ps1

@@ -0,0 +1,15 @@
+Describe "PHP" {
+    Context "PHP" {
+        It "PHP Path" {
+            Get-WhichTool "php" | Should -Not -BeLike "/usr/bin/php*"
+        }
+        It "PHP version" {
+            "php --version" | Should -ReturnZeroExitCode
+        }
+    }
+    Context "Composer" {
+        It "Composer" {
+            "composer --version" | Should -ReturnZeroExitCode
+        }
+    }
+}