Kevin Newton kddnewton

Faster Rails tests

Feedback loop speed in one of the biggest contributing factors to overall development time. The faster you get results, the faster you can move on to other things. A fast enough test suite is therefore critical to teams' success, and is worth investing some time at the beginning to save in the long run.

Below is a list of techniques for speeding up a Rails test suite. It is not comprehensive, but should definitely provide some quick wins. This list of techniques assumes you're using minitest, but most everything should translate over to rspec by simply replacing test/test_helper.rb with spec/spec_helper.rb.

Lead with data
bcrypt
bootsnap
Cache Time::utc calls

	#!/usr/bin/env ruby

	# The purpose of this script is to extract all constant references from a given
	# source file. It reads ARGF, which means you can either pass the content in
	# through stdin or you can pass the file name as an argument. So for example,
	# you can either:
	#
	# echo 'Foo::Bar' \| ./constants
	#
	# or you can pass a file name, as in:

	require "json"

	struct = { "a" => 1, "b" => 2, "c" => [1, 2, 3], "d" => [{ "e" => 3 }, nil, false, true, [], {}] }
	source = JSON.dump(struct)

	tokens = []
	index = 0

	until source.empty?
	tokens <<

	/// This is the opcode of the instruction.
	enum Op {
	Add,
	Sub,
	Mov,
	}

	/// This is a reference to a register. It is passed around when generating the
	/// IR through the Assembler struct. When it gets loaded into an Insn struct as
	/// part of a generated instruction, it is wrapped into an Opnd::Reg.

	# frozen_string_literal: true

	module ActiveRecord
	class Migration
	class MigrationError < StandardError
	end

	RenameColumn = Struct.new(:table_name, :column_name, :new_column_name, keyword_init: true)
	RemoveColumn = Struct.new(:table_name, :column_name, keyword_init: true)
	AddColumn = Struct.new(:table_name, :column_name, :type, :options, keyword_init: true)

	words = []
	letters = ("a".."z").to_a

	File.foreach("/usr/share/dict/words", chomp: true) do \|word\|
	words << word.downcase if word.match?(/\A[a-z]{5}\z/i)
	end

	while words.length > 1
	weights = letters.to_h { \|letter\| [letter, 0] }
	words.each do \|word\|

	def count_constant_refs(iseq)
	cached = false

	iseq.last.each_with_object([]) do \|insn, counts\|
	case insn
	in [:opt_getinlinecache, *]
	cached = true
	counts << 0
	in [:getconstant, *]
	counts[counts.length - 1] += 1 if cached

	# frozen_string_literal: true

	require 'ripper'

	# A Ripper parser that will replace usage of Sorbet patterns with whitespace so
	# that location information is maintained but Sorbet methods aren't called.
	class Eraser < Ripper
	# Represents a line in the source. If this class is being used, it means that
	# every character in the string is 1 byte in length, so we can just return the
	# start of the line + the index.