diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3e0d06dc..e55e85a1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,12 +8,15 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 
 ### Changed
+- Unit tests and examples are now executed alphabetically by filename
 
 ### Deprecated
 
 ### Removed
 
 ### Fixed
+- Library installation no longer "fails" if the library is already installed
+- Platform definition for `mega2560` now includes proper AVR compiler flag
 
 ### Security
 
diff --git a/lib/arduino_ci/arduino_cmd.rb b/lib/arduino_ci/arduino_cmd.rb
index 88e8a818..c5787a1f 100644
--- a/lib/arduino_ci/arduino_cmd.rb
+++ b/lib/arduino_ci/arduino_cmd.rb
@@ -190,7 +190,10 @@ def install_boards(boardfamily)
     # @param name [String] the library name
     # @return [bool] whether the command succeeded
     def _install_library(library_name)
-      success = run_and_capture(flag_install_library, library_name)[:success]
+      result = run_and_capture(flag_install_library, library_name)
+
+      already_installed = result[:err].include?("Library is already installed: #{library_name}")
+      success = result[:success] || already_installed
 
       @libraries_indexed = (@libraries_indexed || success) if library_name == WORKAROUND_LIB
       success
@@ -237,7 +240,7 @@ def library_present?(library_name)
     def update_library_index
       # install random lib so the arduino IDE grabs a new library index
       # see: https://github.com/arduino/Arduino/issues/3535
-      install_library("USBHost")
+      install_library(WORKAROUND_LIB)
     end
 
     # use a particular board for compilation
@@ -319,7 +322,7 @@ def library_examples(installed_library_path)
         proj_file = example_path + e + "#{e}.ino"
         proj_file.exist? ? proj_file.to_s : nil
       end
-      files.reject(&:nil?)
+      files.reject(&:nil?).sort_by(&:to_s)
     end
   end
 end
diff --git a/lib/arduino_ci/cpp_library.rb b/lib/arduino_ci/cpp_library.rb
index ed338a9e..ce632a68 100644
--- a/lib/arduino_ci/cpp_library.rb
+++ b/lib/arduino_ci/cpp_library.rb
@@ -109,7 +109,8 @@ def cpp_files_in(some_dir)
       real = some_dir.realpath
       files = Find.find(real).map { |p| Pathname.new(p) }.reject(&:directory?)
       cpp = files.select { |path| CPP_EXTENSIONS.include?(path.extname.downcase) }
-      cpp.reject { |path| path.basename.to_s.start_with?(".") } # ignore hidden
+      not_hidden = cpp.reject { |path| path.basename.to_s.start_with?(".") }
+      not_hidden.sort_by(&:to_s)
     end
 
     # CPP files that are part of the project library under test
diff --git a/misc/default.yml b/misc/default.yml
index 6ee00ce4..c4baff87 100644
--- a/misc/default.yml
+++ b/misc/default.yml
@@ -98,6 +98,7 @@ platforms:
     gcc:
       features:
       defines:
+        - __AVR_ATmega2560__
       warnings:
       flags:
   cplayClassic: