.guardian.yml

files: ./spec/**/*_spec.cr                                                                                                                                                                                         
run: crystal spec %file%                                                                                                                                                                                           
---                                                                                                                                                                                                                
files: ./src/**/*.cr                                                                                                                                                                                               
run: crystal spec                                                                                                                                                                                                  
---                                                                                                                                                                                                                
files: ./shard.yml                                                                                                                                                                                                 
run: crystal deps  

Guardfile

def crystal_spec_runner(match)                                                                                                                                                                                     
  n match[0], 'File Changed'                                                                                                                                                                                       
  puts match[0] + ' File Changed'                                                                                                                                                                                  
  spec_file = if match[0].start_with?("spec/")                                                                                                                                                                     
    match[0]                                                                                                                                                                                                       
  else                                                                                                                                                                                                             
    "spec/#{match[0].gsub('src/', '')[0..-4]}_spec.cr"                                                                                                                                                             
  end                                                                                                                                                                                                              
  if File.exists?(spec_file)                                                                                                                                                                                       
    puts %x( crystal spec #{spec_file} )                                                                                                                                                                           
    if $?.exitstatus == 0                                                                                                                                                                                          
      puts "#{spec_file} success"                                                                                                                                                                                  
      n match[0], "#{spec_file} success", :success                                                                                                                                                                 
    else                                                                                                                                                                                                           
      puts "#{spec_file} failed"                                                                                                                                                                                   
      n match[0], "#{spec_file} failed", :failed                                                                                                                                                                   
    end                                                                                                                                                                                                            
  else                                                                                                                                                                                                             
    puts "#{spec_file} not found"                                                                                                                                                                                  
    n match[0], "#{spec_file} not found", :pending                                                                                                                                                                 
  end                                                                                                                                                                                                              
end                                                                                                                                                                                                                
                                                                                                                                                                                                                   
guard :shell do                                                                                                                                                                                                    
  watch(/src\/(.*).cr/)       { |m| crystal_spec_runner(m) }                                                                                                                                                       
  watch(/spec\/(.*)_spec.cr/) { |m| crystal_spec_runner(m) }                                                                                                                                                       
end