Rewrite `with_history` test helper to be more robust

Write mock history to a temp file and load it directly with `fc -R`
instead of running each command individually to build up the history.

spec/multi_line_spec.rb

@@ -1,11 +1,6 @@
 describe 'a multi-line suggestion' do
   it 'should be displayed on multiple lines' do
-    with_history(-> {
-      session.send_string('echo "')
-      session.send_keys('enter')
-      session.send_string('"')
-      session.send_keys('enter')
-    }) do
+    with_history("echo \"\n\"") do
       session.send_keys('e')
       wait_for { session.content }.to eq("echo \"\n\"")
     end

spec/spec_helper.rb

@@ -1,6 +1,7 @@
 require 'pry'
 require 'rspec/wait'
 require 'terminal_session'
+require 'tempfile'
 
 RSpec.shared_context 'terminal session' do
   let(:term_opts) { {} }
@@ -21,11 +22,12 @@ RSpec.shared_context 'terminal session' do
   end
 
   def with_history(*commands, &block)
-    session.run_command('fc -p')
+    Tempfile.create do |f|
+      f.write(commands.map{|c| c.gsub("\n", "\\\n")}.join("\n"))
+      f.flush
 
-    commands.each do |c|
-      c.respond_to?(:call) ? c.call : session.run_command(c)
-    end
+      session.run_command('fc -p')
+      session.run_command("fc -R #{f.path}")
 
       session.clear_screen
 
@@ -34,6 +36,7 @@ RSpec.shared_context 'terminal session' do
       session.send_keys('C-c')
       session.run_command('fc -P')
     end
+  end
 end
 
 RSpec.configure do |config|