1 Aurora InnovationContinuous Regression Testing for Safer and Faster Refactoring Pejman Ghorbanzade Aurora Innovation3 Aurora Innovation Engineers spend 17 hours per week maintaining software. *Stripe *Stripe 2019 Developer Coef�cient Report4 Aurora Innovation Maintaining Software Reading Refactoring Upgrading Migrating Debugging Adding tests Writing documentation Resolving technical debt “The

1● Who Am I ● Refactoring Tooling Use Cases ● Clang Crash Course ● Writing a Clang Tidy Check Live ● Special Thanks & Questions Agenda 2Who Am I 01 3Proprietary + Confidential C++ Core Libraries Core Libraries 9Proprietary + Confidential Large Scale Refactorings & Automated Refactoring Tools 10 10Refactoring Tool Use Cases 02 11Proprietary + Confidential Consistent Code Formatting 12 hasType(isInteger())))))), this) }So you have a node SO WHAT? 70 70Be Yourself So you have a node 71 71Refactoring 06 72 72The Bound Nodes 73 73 void check(const ast_matchers::MatchFinder::MatchResult &Result)

ROS 2 ● ROS 2 Conventional Approach ● Introduction to Functional Programming Principles ● Refactoring using Functional Programming Principles ● ConclusionIntroductionAbout Me ● Robotics Engineer services can be assigned ● No need to have a PathGenerator object that inherits from rclcpp::Node Refactoring PathGenerator class PathGenerator : public rclcpp::Node { public: explicit PathGenerator(rclcpp::NodeOptions The private functions of PathGenerator can be turned into free functions and lambda functions Refactoring PathGenerator class PathGenerator : public rclcpp::Node { public: explicit PathGenerator(rclcpp::NodeOptions

string, Cache&, const Data&, ...) { // ... } 61 Bloomberg Refactoring for DIbool execute(Bucket& bucket) { // ... } 62 Bloomberg Refactoring for DI struct Bucket { DB& db_; Com& com_; FileLdr& ldr_; numerous to injectGod-Like Class 64 Bloomberg Refactoring for DI Pricing Sizing Actions Saving Sending Business logic verifying Rules65 Bloomberg Refactoring for DI God-Like Class Pricing Sizing Encapsulated functionality ✓ Unit testing ✓ Refactor ✓ Prelude to DI Glue Logic66 Bloomberg Refactoring for DI God-Like Class Pricing Sizing Actions Saving Sending Distribution Logic Gather Information

configuration manager ■ Hold global configuration values 37 This is the option we want!Time for the refactoring! (1/2) ● The first step is to move our global variables into a class ○ This groups both variables some behaviors (i.e. member functions) for working with these values as well 38Time for the refactoring! (2/2) ● We move our globals into a class and will make them member variables ○ ConfigurationManager ○ Memory is only allocated if you actually use the Singleton ● Cons ○ Wrong usage could take refactoring ■ (i.e. In the case that you need two instances of an object) ○ Not thread-safe, you will have

safe, but they also make it thread inefficient ◉ Keeping a computation lock free may require refactoring to use another approach ◉ Adding a lock might look fine in profiler because another bottleneck isn’t important ◉ No locks are being used 50What if I need to update shared state? 51 🔗Refactoring shared state ◉ Make copies ◉ Split problematic iteration in 2 loops ○ Parallel apply using a to the locking scheme allowed for parallelization ◉ Even better gains could be achieved by refactoring to lock free ◉ But we already reduced from 6.8s to 1.1s 61Making it a problem for the future

Scientific C++ and Qt developer since 1999 • My mission: Sustainable and efficient testing and refactoring of legacy code – Co-author of “Approval Tests for C++” • Consulting & training via “Clare Macrae Needs refactoring to add tests Can’t refactor without tests7 Typical Scenario • • • • • Need to change the code No tests Not designed for testing Needs refactoring to add via: – bit.ly/TestingQt – github.com/claremacrae/talks • Sustainable and efficient testing and refactoring of legacy code • Consulting & training via “Clare Macrae Consulting Ltd” – claremacrae.co.uk

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linters ○ New type-checking ○ Code changes needed to adopt ● A goal to increase test coverage ○ “Refactoring” to make code more testable“X% of your code will be rewritten in 5 years.ˮKubrick, Stanley. 2001 v=v_yzLe-wnfk Maintainability and Refactoring Impact of Higher-Level Design Featureshttps://www.youtube.com/watch?v=torqlZnu9Ag How to Build Your First C Automated Refactoring Toolhttps://www.youtube.com/watch

meant for inclusion should end in .inc. 3 All header files should be self-contained. Users and refactoring tools should not have to adhere to special conditions to include the header. Specifically, a header developers incorrectly use that interface now must explain how the macros formed the interface. Refactoring and analysis tools have a dramatically harder time updating the interface. As a consequence, we user does something wrong. Template metaprogramming interferes with large scale refactoring by making the job of refactoring tools harder. First, the template code is expanded in multiple contexts, and it’s