Merge pull request #720 from kenhys/support-check_is_installed_by_gem

Windows: support check_is_installed_by_gem

lib/specinfra/backend/powershell/support/find_installed_gem.ps1

@@ -0,0 +1,20 @@
+function FindInstalledGem
+{
+  param($gemName, $gemVersion)
+
+  $nameVer = $(Invoke-Expression "gem list --local" | Select-String "$gemName").Line
+  if ($nameVer.StartsWith($gemName)) {
+    if ($gemVersion) {
+      if ($nameVer.EndsWith("$gemVersion)")) {
+        $true
+      } else {
+        $false
+      }
+    } else {
+      $true
+    }
+  } else {
+    $false
+  }
+}
+

lib/specinfra/command/windows/base/package.rb

@@ -7,5 +7,13 @@ def check_is_installed(package, version=nil)
         exec "(FindInstalledApplication -appName '#{package}' #{version_selection}) -eq $true"
       end
     end
+
+    def check_is_installed_by_gem(name, version=nil, gem_binary="gem")
+      version_selection = version.nil? ? "" : "-gemVersion '#{version}'"
+      Backend::PowerShell::Command.new do
+        using 'find_installed_gem.ps1'
+        exec "(FindInstalledGem -gemName '#{name}' #{version_selection}) -eq $true"
+      end
+    end
   end
 end