Kaushik Gopal's Home

Kotlin coroutines testing tip - exploring 3 of the important apis to control virtual time in your tests.

Kotlin coroutines testing tip - using backgroundScope to cancel never ending child coroutines in tests.

Kotlin coroutines testing tip - The most important concept for testing coroutines is knowing how to pick the right Dispatcher

My tried and tested tips on testing Kotlin Coroutines

Use Campground PRs to improve your code before you start on your feature.

I wrote a blog post about git-number and how useful it was for my command line git usage. In an on-going effort to simplify my lifestyle & setup, I replaced git-number with a few git aliases. I’ll explain how I recreated the functionality in this blog post.

Quick video demonstrating kscript + github copilot (unlock your scripting powers)

A shell script that will pull new blog posts from your feed and automatically post to Mastodon.

A few Kotlin constructs have been introduced into the language over time. I wrote this post as a personal/public service advisory to remind us of their significance.

The trick to understanding awk in all its terse glory is to understand its defaults. Most solutions you see in the wild are a clever symphony of awk defaults stacked on top of each other. In this post, I break down one of the most popular one-liners which should hopefully make future awk-ing pretty straight forward.

A fascinating article from 2017 on how coding or programming as a mechanism of writing software is frought with landmines. If you’re a software engineer, this article is a must-read. It took a lot of restraint not to just pull-quote every paragraph from this article.

I’ve been looking into Tufte CSS recently. Tufte CSS -inspired by the teachings of the legendary Edward Tufte1- provides suggestions and tools to style web articles for improved legibility. I’ve started to incorporate some of those principles here while still trying to keep the authenticity of my original design. Most of these changes have been in the realm of CSS however the sidenotes feature was a slightly trickier beast. I’ve implemented this feature in my blog theme “Henry” for both Hugo & Jekyll.

If you’re a software engineer trying to be snarky, it’s important to get these terms right for maximum effect. What is Yak-Shaving? “Shaving a Yak” means performing a seemingly endless series of small tasks that must be completed before the next step in the project can move forward. Is this a good thing or a bad thing? It depends. Yak Shaving is sometimes very much necessary. It’s “bad” only when done unnecessarily.

Two big announcements: I made my first screen cast 1 I’ve updated the permalink title for all the blog posts here 2 I wanted to make sure that external blogs linking to previous post links wouldn’t break. So in order to do this, I had to edit all of my previous blog posts and add a redirect_from tag. Life is too short to be doing this manually so I whipped up an awk program to do it for me in about 20 minutes.

If you’re a programmer these days, you probably spend a large part of your day in git. If you’re a command line zealot like me, you realize the holy ways of using your Terminal app for everything and aren’t seduced by fancy GUIs that only stand to dissuade you from pure unbridled productivity. With that in mind, one typically finds themselves in a position where they have a few files that have changed liked so:

This blog now 1 uses Jekyll - a static blog generator that takes markdown as an input and pumps html as output. I then copy it over to my hosting server - Firebase, which then happily serves it to the interwebs. This setup has worked out swimmingly well thus far and has been rock solid. Even when my last post got high up the ranks of HN, my blog held steady.

The TestObserver is an RxJava staple for testing. It allows you to assert values in a stream, in the specific order they were emitted. Here’s a quick code snippet from the movies-usf repository 1: @Test fun onSearchingForMovieBladeRunner_shouldSeeSearchResult() { viewModel = MSMainVm(mockApp, mockMovieRepo) val viewStateTester = viewModel.viewState.test() viewModel.processInput(SearchMovieEvent("blade runner 2049")) viewStateTester.assertValueAt(1) { assertThat(it.searchedMovieTitle).isEqualTo("Searching Movie...") true } viewStateTester.assertValueAt(2) { assertThat(it.searchedMovieTitle).isEqualTo("Blade Runner 2049") // ... true } } If you look at the source for the base TestObserver, there are a bunch of these useful methods:

This super intesting stack overflow answer explains why -in programming- if you have a sorted array, somehow magically it can seem like it’s easier to process each element vs processing the same array if it were unsorted. tl;dr - branch prediction With a sorted array, the condition data[c] >= 128 is first false for a streak of values, then becomes true for all later values. That’s easy to predict. With an unsorted array, you pay for the branching cost.

Sometime back I ran across a thread where folks talked about this programming style called “Space Shuttle style” that the Kubernetes codebase followed. // ================================================================== // PLEASE DO NOT ATTEMPT TO SIMPLIFY THIS CODE. // KEEP THE SPACE SHUTTLE FLYING. // ================================================================== // // This controller is intentionally written in a very verbose style. You will // notice: // // 1. Every 'if' statement has a matching 'else' (exception: simple error // checks for a client API call) // 2.

This is a fantastic post by Erik where he explains the nuance between IO-bound and CPU-bound operations in programming. … libraries have dedicated APIs for I/O scheduling work, separate from other types of operations …. but why is this the case? Why don’t we use a single thread pool for all background operations? The operating system will handle the scheduling of these threads the same I love how this specific question is framed (a good interview question for advanced mobile developers):

A not so well known api in RxJava is the .hide() operator. When does one use the hide operator in Rx? From the docs: Hides the identity of this Observable and its Disposable. Allows hiding extra features such as Subject’s Observer methods or preventing certain identity-based optimizations (fusion). there are a lot of complex operations that take place internally in RxJava (like internal queue creation, worker instantiation + release, numerous atomic variables being created and modified.

This feature is beneficial for projects defining custom source sets, since the compilation of independent source sets can be parallelized. In the case of multiplatform projects, targets for different platforms can also be built in parallel. For Android, the debug and release build types can be compiled in parallel. This sounds pretty cool, however I paused to think how often would i need the debug and release build types to be compiled in parallel?

We recently held our semi-annual hackathon at Instacart - the Carrot Wars 2018! In putting this hackathon together, I noticed a pretty blaring gap - there wasn’t a simple (and free) online service that would quickly tabulate the results for a hackathon event. We looked around and found some nifty options, but most of them were a tad bit too expensive for our liking. They also were not setup for a single event use or required a monthly subscription.

Checkout this quick blog post I wrote for my company, tweaking the existing Kotlin TODO to work towards our requirements. While I don’t think this solution is a panacea for all your missing code snippets, I have found some luck with this method, in adding accountability for those PR review feedback comments you say you’ll get to, but conveniently forget :) Here’s a bonus if you’re reading this article from here:

In case you haven’t heard: RxJava2 was released sometime back. RxJava 2 was a massive rewrite with breaking apis (but for good reasons). Most dependent libraries have upgraded by now though, so you’re safe to pull that migration trigger with your codebases. Folks starting out directly with Rx2 might enjoy this guide but it’s the ones that started with Rx 1 that will probably appreciate it the most. This is a continuation post in a 2 part series:

This is a continuation post in a 2 part series: Understanding the changes Disposing subscriptions Disposing Subscriptions This was the part that I initially found most tricky to grasp but also most important to know as an AndroidDev (memory leak and all). Jedi master Karnok explains this best in the wiki: In RxJava 1.x, the interface rx.Subscription was responsible for stream and resource lifecycle management, namely unsubscribing a sequence and releasing general resources such as scheduled tasks.

A common question most android developers have when using RxJava is: how do I cache or persist the work done by my observables over a configuration change? If you start a network call and the user decides to rotate the screen, the work spent in executing that network call would have been in vain (considering the OS would re-create your activity). There are two widely accepted solutions to this problem:

hear ye, hear ye! the 2nd episode of the Fragmented Podcast is out. Donn and i start by discussing Lamas, blue dresses and IDEs for Android development!

i spent a huge part of my 2014 on “Rx” (or reactive extensions) which is essentially a library that helps with a development pattern called “reactive programming”. i think Rx is going to be huge in the app development world. it’s already picked up a lot of steam, but i think it’s going to become a staple for professional app developers. consider this extremely common scenario: you’re in Burundi surfing facebook.

Originally posted this article on the Wedding Party tech blog Ok, so in my previous post I innocuously introduced the .share() operator. Observable<Object> tapEventEmitter = _rxBus.toObserverable().share(); What is this share operator? The .share() operator is basically just a wrapper to the chained call .publish().refcount(). You’ll find the chained combo .publish().refcount() used in quite a few Rx examples on the web. It allows you to “share” the emission of the stream.

i listen to a tonne of podcasts. i find activities such as doing my laundry, driving back home from work, doing the dishes … all delightful because it gives me a chance to strap on some headphones and listen to a bunch of podcasts. in the time that i run those dreadfully boring chores i’ve found myself learning so much about technology and good software development. as i was driving back home today i was listening to an episode of Ruby Rogues and thought to myself:

Originally posted this article on the Wedding Party tech blog This is a bonus RxJava post that I landed up writing along with my previous post on creating an event bus with RxJava. If you went through the code in the actual repo you would have noticed more than one version of the bottom fragment in the RxBus demo. Originally I envisioned the RxBus example being a tad bit fanicer however as I coded up the example, I realized that too many concepts were getting conflated.

Originally posted this article on the Wedding Party tech blog This post has three parts: quick primer on what an event bus is implementing the event bus with RxJava parting thoughts on this approach “RxBus” is not going to be a library. Implementing an event bus with RxJava is so ridiculously easy that it doesn’t warrant the bloat of an independent library. Part 1: What is an event bus? Let’s talk about two concepts that seem similar: the Observer pattern and the Pub-sub pattern.

Originally posted this article on the Wedding Party tech blog I’ve read and watched a lot on Rx. Most examples either use the J8 lambda notations/Scala/Groovy or some other awesome language that us Android developers are constantly envious of. Unfortunately I could never find real-world simple examples in Android that could show me how to use RxJava. To scratch that itch, I created a github repo with a couple of nifty examples using RxJava.

Originally posted this article on the Wedding Party tech blog Mobile devices are getting pretty fast, but they aren’t infinitely fast yet. If you want your app to be able to do any serious work without affecting the user experience by locking up the interface, you’ll have to resort to running things in parallel. On Android, this is done with “threads”. Grab yourself a cup of coffee and read this post line by line.

This is by far the funniest stuff I’ve read this year. Never fails to crack me up…

There’s something innately comforting about coding. The solution is not known but the variables are fixed. The ambiguities are minimal and the choices are simple. The rule book is adhered to. You mess up and you get bugs, you get it right and a solution is reached. If the solution is good, it becomes poetry. I realize why management have it tough now. The jargon, documentation, definitions, ambiguity and interpretations that they have to deal with are such a mess.

… You should mention what technologies you are using (because listing WCF or Java will save me the hassle of applying, and you the hassle of rejecting me), but don’t list specific tools, languages and frameworks as requirements. Good developers who know Rails can learn Django or Node. Going between Oracle, SQL Server, MySQL and Postgres is all pretty trivial. … I remember being asked quite eagerly, during a pre-interview, if I knew a specific view engine (like erb, or haml…).

Dr.Neil Degrasse Tyson on the Verge: .. the bulk of the Androids get their time from GPS satellites.. The time keeping bases for the GPS satellites was defined upto 1982 and since 1982, 15 seconds have been added to civil time and that 15s is not included in the Andorid time keeping settings (because their getting their time directly from GPS), whereas the iPhone compensates for this and puts the 15s backs in…

If you’re in the business of hiring programmers, the article linked is a must read. It’s concise and a gold read. No excuse for not reading it. Avoid nano-questions A good engineer thinks abstractly in terms of designing and building systems, they think in terms of algorithms, components, and engineering design. They do not necessarily know all of the details of syntax of a given language, especially if they are used to a good IDE… … it is more important that I be able to tell you when and where I should use inheritance, and when and where I should use polymorphism, than to be able to spit off the definition.

definitely dated, but interesting yardsticks. via Hacker News

You’d be surprised how valuable the skill of eloquent communication is even in the field of IT. Keeping users apprised with your progress is perhaps the most important thing to do when working with clients. But keeping them apprised is tricky business and the ability to clearly put down in words,what to expect, is a basic necessity today. Even if you have nothing to do with CS or computers, you should read the linked article.

What you need to know about RAM, memory, CPU Processing and other important stuff that could tell you why your computer is slow. Physical RAM/Memory RAM chips funcion quite literally like your Computer’s Memory. All the information that needs to be remembered when operating between different tasks (or even the same task) gets stored here. You know how people who have great memories can be awesome, that translates to the computer world as well, more memory = more awesome.

#2024

#2023

#2022

#2020

#2019

#2018

#2017

#2015

#2014

#2013

#2012

#2011