Add ArduinoBackend.boards_installed?

Author: ianfixes

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - `Wire.resetMocks()` and documentation
 - `shiftIn()` and `shiftOut()`
 - `CIConfig.is_default` to detect when the default configuration is used
+- `ArduinoBackend.boards_installed?` to detect whether a board family (or package, like `arduino:avr`) is installed
 
 ### Changed
 - Rubocop expected syntax downgraded from ruby 2.6 to 2.5

lib/arduino_ci/arduino_backend.rb

@@ -113,10 +113,17 @@ def board_manager_urls=(all_urls)
     # @param boardname [String] The board to test
     # @return [bool] Whether the board is installed
     def board_installed?(boardname)
-      # capture_json("core", "list")[:json].find { |b| b["ID"] == boardname } # nope, this is for the family
       run_and_capture("board", "details", "--fqbn", boardname)[:success]
     end
 
+    # check whether a board family is installed (e.g. arduino:avr)
+    #
+    # @param boardfamily_name [String] The board family to test
+    # @return [bool] Whether the board is installed
+    def boards_installed?(boardfamily_name)
+      capture_json("core", "list")[:json].any? { |b| b["ID"] == boardfamily_name }
+    end
+
     # install a board by name
     # @param name [String] the board name
     # @return [bool] whether the command succeeded