A rake runner for minitest, capturing the outcome of the test

minitest_rake_runner.rb

# app/services/minitest_rake_runner.rb
require 'open3'

class MinitestRakeRunner
  attr_reader :stdout_lines

  class RakefileMissingError < StandardError; end

  PATTERN = /(?<tests>\d+) (tests|runs), (?<assertions>\d+) assertions, (?<failures>\d+) failures, (?<errors>\d+) errors, (?<skips>\d+) skips/

  def run(directory)
    check_for_rakefile! directory
    stdin, stdout, stderr = Open3.popen3('rake', chdir: directory)
    @stdout_lines = stdout.readlines
    parse_stdout
  end

  private

    def parse_stdout
      @stdout_lines.reverse.each do |line|
        result = PATTERN.match line
        if result
          return Hash[result.names.collect(&:to_sym).
                      zip(result.captures.collect(&:to_i))]
        end
      end
    end

    def check_for_rakefile!(directory)
      unless File.exists?(File.join(directory, 'Rakefile'))
        raise RakefileMissingError.new("Could not find any Rakefile in #{directory}")
      end
    end
end

minitest_rake_runner_spec.rb

describe MinitestRakeRunner do
  let(:runner) { MinitestRakeRunner.new }
  let(:rake_directory) { File.expand_path("../../support/minitest_rake_runner/has_rake_file", __FILE__)}
  let(:no_rake_directory) { File.expand_path("../../support/minitest_rake_runner/no_rake_file", __FILE__)}

  describe "#run" do
    it "should raise if the directory does not have a rakefile" do
      expect { runner.run(no_rake_directory) }.to raise_error  MinitestRakeRunner::RakefileMissingError
    end

    it "should not raise if the directory has a rakefile" do
      expect { runner.run(rake_directory) }.not_to raise_error
    end

    it "should return the minitest results" do
      result = runner.run(rake_directory)
      expect(result[:tests]).to eq 1
      expect(result[:assertions]).to eq 1
      expect(result[:failures]).to eq 0
      expect(result[:errors]).to eq 0
      expect(result[:skips]).to eq 0
    end

    it "should expose the stdout of the rake job" do
      runner.run(rake_directory)
      expect(runner.stdout_lines).not_to be_blank
    end
  end
end