Update tests to work with sshkit master / no user

This accounts for changes in sshkit's local username lookup introduced
by capistrano/sshkit#293 and also accounts for the conditional
formatting changes introduced by mattbrictson#66.

The latter did not previously cause failed tests, because the username
was stubbed in the tests, causing the relevant code to not be exercised.

Now the username is looked up through sshkit, which results in an empty
username on sshkit < 1.7.0, so the no-username display is triggered.

Unfortunately we need to keep the Etc stub for now to avoid crashing on
Windows with sshkit 1.7.0 and 1.7.1.

test/airbrussh/formatter_test.rb

@@ -11,13 +11,11 @@ class Airbrussh::FormatterTest < Minitest::Test
   def setup
     @output = StringIO.new
     @log_file = StringIO.new
-    @user = "test_user"
-
-    # Force a consistent username when SSHKit::Backend::Local is used.
-    # This is also necessary to work around a Windows-specific bug in SSHKit,
-    # where it relies on Etc.getpwuid to get the username, even though this
-    # doesn't work on Windows.
-    Etc.stubs(:getpwuid => stub(:name => @user))
+    # sshkit > 1.6.1 && <= 1.7.1 uses Etc.getpwuid.name for local user lookup
+    # which causes a NoMethodError on Windows, so we need to stub it here.
+    Etc.stubs(:getpwuid => stub(:name => "stubbed_user")) unless sshkit_after?("1.7.1")
+    @user = SSHKit::Host.new(:local).username # nil on sshkit < 1.7.0
+    @user_at_localhost = [@user, "localhost"].compact.join("@")
   end
 
   def teardown
@@ -52,7 +50,7 @@ def test_formats_execute_with_color
     assert_output_lines(
       "      01 \e[0;33;49mecho foo\e[0m\n",
       "      01 foo\n",
-      /    \e\[0;32;49m✔ 01 #{@user}@localhost\e\[0m \e\[0;90;49m\d.\d+s\e\[0m\n/
+      /    \e\[0;32;49m✔ 01 #{@user_at_localhost}\e\[0m \e\[0;90;49m\d.\d+s\e\[0m\n/
     )
 
     assert_log_file_lines(
@@ -75,7 +73,7 @@ def test_formats_execute_without_color
     assert_output_lines(
       "      01 echo foo\n",
       "      01 foo\n",
-      /    ✔ 01 #{@user}@localhost \d.\d+s\n/
+      /    ✔ 01 #{@user_at_localhost} \d.\d+s\n/
     )
 
     assert_log_file_lines(
@@ -94,7 +92,7 @@ def test_formats_without_command_output
 
     assert_output_lines(
       "      01 ls -l\n",
-      /    ✔ 01 #{@user}@localhost \d.\d+s\n/
+      /    ✔ 01 #{@user_at_localhost} \d.\d+s\n/
     )
   end
 
@@ -121,7 +119,7 @@ def test_formats_failing_execute_with_color
     expected_output = [
       "      01 \e[0;33;49mecho hi\e[0m\n",
       "      01 hi\n",
-      /    \e\[0;32;49m✔ 01 #{@user}@localhost\e\[0m \e\[0;90;49m\d.\d+s\e\[0m\n/,
+      /    \e\[0;32;49m✔ 01 #{@user_at_localhost}\e\[0m \e\[0;90;49m\d.\d+s\e\[0m\n/,
       "      02 \e[0;33;49mls _file_does_not_exist\e[0m\n"
     ]
 
@@ -163,7 +161,7 @@ def test_formats_capture_with_color
     assert_output_lines(
       "      01 \e[0;33;49mls -1 airbrussh.gemspec\e[0m\n",
       "      01 airbrussh.gemspec\n",
-      /    \e\[0;32;49m✔ 01 #{@user}@localhost\e\[0m \e\[0;90;49m\d.\d+s\e\[0m\n/
+      /    \e\[0;32;49m✔ 01 #{@user_at_localhost}\e\[0m \e\[0;90;49m\d.\d+s\e\[0m\n/
     )
 
     assert_log_file_lines(
@@ -183,7 +181,7 @@ def test_formats_capture_without_color
     assert_output_lines(
       "      01 ls -1 airbrussh.gemspec\n",
       "      01 airbrussh.gemspec\n",
-      /    ✔ 01 #{@user}@localhost \d.\d+s\n/
+      /    ✔ 01 #{@user_at_localhost} \d.\d+s\n/
     )
 
     assert_log_file_lines(
@@ -235,20 +233,20 @@ def test_handles_rake_tasks
       "00:00 special_rake_task\n",
       "      01 echo command 1\n",
       "      01 command 1\n",
-      /    ✔ 01 #{@user}@localhost \d.\d+s\n/,
+      /    ✔ 01 #{@user_at_localhost} \d.\d+s\n/,
       "      Starting command 2\n",
       "      02 echo command 2\n",
       "      02 command 2\n",
-      /    ✔ 02 #{@user}@localhost \d.\d+s\n/,
+      /    ✔ 02 #{@user_at_localhost} \d.\d+s\n/,
       "00:00 special_rake_task_2\n",
       "      New task starting\n",
       "00:00 special_rake_task_3\n",
       "      01 echo command 3\n",
       "      01 command 3\n",
-      /    ✔ 01 #{@user}@localhost \d.\d+s\n/,
+      /    ✔ 01 #{@user_at_localhost} \d.\d+s\n/,
       "      02 echo command 4\n",
       "      02 command 4\n",
-      /    ✔ 02 #{@user}@localhost \d.\d+s\n/,
+      /    ✔ 02 #{@user_at_localhost} \d.\d+s\n/,
       "      All done\n"
     )
 
@@ -314,14 +312,14 @@ def test_interleaved_debug_and_info_commands
       "00:00 interleaving_test\n",
       "      01 echo command 1\n",
       "      01 command 1\n",
-      /    ✔ 01 #{@user}@localhost \d.\d+s\n/,
+      /    ✔ 01 #{@user_at_localhost} \d.\d+s\n/,
       "      Info line should be output\n",
       "      02 echo command 2\n",
       "      02 command 2\n",
-      /    ✔ 02 #{@user}@localhost \d.\d+s\n/,
+      /    ✔ 02 #{@user_at_localhost} \d.\d+s\n/,
       "      03 echo command 4\n",
       "      03 command 4\n",
-      /    ✔ 03 #{@user}@localhost \d.\d+s\n/
+      /    ✔ 03 #{@user_at_localhost} \d.\d+s\n/
     )
   end
 
@@ -330,11 +328,6 @@ def test_interleaved_debug_and_info_commands
   def on_local(task_name=nil, &block)
     define_and_execute_rake_task(task_name) do
       local_backend = SSHKit::Backend::Local.new(&block)
-      # Note: The Local backend default log changed to include the user name around version 1.7.1
-      # Therefore we inject a user in order to make the logging consistent in old versions (i.e. 1.6.1)
-      unless sshkit_after?("1.6.1")
-        local_backend.instance_variable_get(:@host).user = @user
-      end
       local_backend.run
     end
   end
@@ -367,7 +360,7 @@ def assert_log_file_lines(*command_lines)
 
   def command_running(command, level="INFO")
     level_tag_color = (level == "INFO") ? :blue : :black
-    /#{send(level_tag_color, level)} \[#{green('\w+')}\] Running #{bold_yellow("#{command}")} as #{blue(@user)}@#{blue('localhost')}\n/
+    /#{send(level_tag_color, level)} \[#{green('\w+')}\] Running #{bold_yellow("#{command}")} #{@user ? "as #{blue(@user)}@" : "on "}#{blue('localhost')}\n/
   end
 
   def command_started_debug(command)