Fixing Flaky Oppia CI: Story & Chapter Management Tests

Hey guys! Ever hit a roadblock where something just refuses to work consistently? That's exactly the kind of headache we're diving into today with a recent Oppia CI failure. We're talking about those pesky flaky tests that pop up in our E2E/Acceptance CI pipeline, specifically impacting the critical area of topic manager operations: creating, deleting, and editing stories and chapters within the Oppia platform. These E2E Acceptance tests are super important because they simulate real user interactions, ensuring that everything from a new story creation to a chapter edit works exactly as intended for our awesome educators and learners. When they start failing inconsistently, it's not just a minor glitch; it can seriously slow down development and deployment, making us wonder if our new features are truly stable. This particular failure occurred on mobile, adding another layer of complexity to our debugging efforts. Our goal here is to unpack what happened, understand why these tests are exhibiting flakiness, and brainstorm some solid strategies to make our story and chapter management tests rock-solid reliable. We want to ensure that our Oppia CI pipeline runs smoothly, giving us confidence that every change we push contributes to a robust and engaging learning platform. So, buckle up, because we're about to get to the bottom of this flakiness and pave the way for a more stable Oppia experience. Let's make sure our continuous integration system is as strong and dependable as the educational content it helps deliver!

Understanding the Oppia CI Failure: What Went Wrong?

Alright, let's break down this specific Oppia CI failure and pinpoint the issues. The core problem manifested during an E2E Acceptance test designed to ensure the topic manager can seamlessly create, delete, and edit stories and chapters. This test, crucial for validating our story and chapter management features, choked on mobile, which immediately raises a few eyebrows given the diverse environments Oppia operates in. The first major red flag in the stacktrace pointed to a rather cryptic but unfortunately common JavaScript error: Cannot read properties of undefined (reading 'getStory'). This happened right when the system was trying to load a story within the story editor, specifically at the /story_editor/prAbBeoE8AMi#/chapter_editor/node_1 URL. For those unfamiliar, this error generally means that the code expected a JavaScript object to have a getStory property, but the object itself was undefined, essentially non-existent or not yet loaded. Imagine trying to read a specific page from a book that hasn't even arrived yet – that's the kind of fundamental data availability issue we're talking about here. This type of error often suggests a race condition or an asynchronous operation that didn't complete as expected before the next part of the test script tried to interact with the story data. It's a classic example of the front-end trying to do something with data that the back-end hasn't fully provided, or perhaps a component hasn't rendered correctly to expose the expected data structure. Fixing this kind of error is critical for the stability of our Oppia CI pipeline, as it directly impacts the ability to manage educational content.

Following this, the second significant hiccup was a TimeoutError. This bad boy reared its head when an element, specifically one needed to save chapters with mobile-supported explorations, took too long to be clickable. The error message, "Element with selector JSHandle@node took too long to be clickable. Original Error: waiting for function failed: timeout 30000ms exceeded," clearly tells us that our automated test script, using Puppeteer, waited for a whopping 30 seconds for a crucial UI element to become interactive, and it simply never did. This often happens in automated tests when an element is either not rendered on time, is obscured by another element, or perhaps some underlying JavaScript is still processing, preventing it from becoming interactable. For our topic manager tests, this TimeoutError is a strong indicator of a performance bottleneck or a rendering issue, especially on mobile where resources might be tighter or network latency more impactful. The final blow came with a "Chapter with name Simple Exploration not found" error, which, let's be honest, is likely a cascading effect of the previous failures. If the story data couldn't be loaded or the chapter couldn't be saved due to a clickable element timeout, then naturally, the system wouldn't be able to find it later for editing or previewing. These E2E Acceptance CI failures, particularly the flakiness in story and chapter management, highlight that we need to scrutinize not just our test scripts but also the underlying application's robustness, especially concerning data loading and UI responsiveness on mobile devices. Ensuring these fundamental interactions are smooth is paramount for a reliable Oppia CI.

The Dreaded Cannot read properties of undefined (reading 'getStory') Error

Let's get down to the nitty-gritty of that Cannot read properties of undefined (reading 'getStory') error. This specific issue, appearing when navigating to the chapter editor within the story editor, is a major headache because it points to a fundamental problem with how story data is being accessed or made available. In simple terms, our application was trying to pull information about a story, using a function called getStory, but the object it was trying to call getStory on didn't exist or wasn't properly initialized. Think of it like trying to ask a specific question to someone who isn't even in the room yet! This often occurs in single-page applications (SPAs) like Oppia, where content is loaded dynamically. Potential causes for this Oppia CI failure include: 1) Race Conditions: The test script might be moving too fast, trying to interact with the story editor before the necessary data (the story object itself) has fully loaded from the server or been processed by the front-end. 2) Asynchronous Loading Issues: The getStory method might rely on data that's fetched asynchronously. If there's no proper loading state or error handling, the application tries to use the data before it's ready, leading to an undefined state. 3) Component Lifecycle Problems: Perhaps a component responsible for fetching or setting the story object is not mounted or initialized correctly on mobile, or its lifecycle hooks aren't firing in the expected order, leading to the story variable being undefined when getStory is called. This kind of flakiness in our story and chapter management tests is deeply concerning because it suggests a brittle connection between our UI and its underlying data models. To fix this, we'll need to meticulously trace the data flow for stories and chapters, ensuring that getStory is only invoked when the story object is guaranteed to be present. This might involve adding more robust loading indicators, explicit waits in our test scripts for data to be available, or refining the component's state management to prevent premature data access.

TimeoutError: When Elements Don't Cooperate

Then there's the equally frustrating TimeoutError, which indicates that an element crucial for saving chapters simply wasn't clickable within the allotted 30 seconds. This is a common nemesis in E2E Acceptance testing and often points to a complex interplay of factors, especially on mobile. When our waitForElementToBeClickable function fails, it essentially means the UI element—the one we expect users to click to save their hard work—was never in a state where an interaction could occur. The original error, "waiting for function failed: timeout 30000ms exceeded," highlights that our script patiently waited, but the element just wasn't ready. Why does this happen, especially when we're talking about story and chapter management tests on mobile? Several reasons could contribute to this type of Oppia CI failure: 1) Rendering Delays: On mobile devices, which might have slower processors or less memory, complex UI components can take longer to render. The element might visually appear, but its underlying JavaScript event listeners might not be fully attached or active. 2) Overlaying Elements: Sometimes, another invisible or transient element might be briefly covering the target element, preventing it from being considered clickable by the automation tool. This is particularly tricky to debug without visual inspection. 3) Network Latency: If saving the chapter involves a network request, and the UI element's clickability depends on the response or a subsequent state update, slow network conditions (even in a simulated CI environment) can cause delays. 4) JavaScript Execution Blocks: Heavy JavaScript computations running in the background might temporarily block the main thread, making the UI unresponsive and preventing elements from becoming interactive. This TimeoutError is a prime suspect for test flakiness because it's often intermittent and highly dependent on the exact timing and performance characteristics of the testing environment. To address this, we'll need to implement more intelligent waiting strategies in our Puppeteer tests, perhaps waiting for specific API calls to resolve or for certain DOM attributes to appear, rather than just general clickability. We might also need to investigate the performance of the chapter saving mechanism itself on mobile, ensuring that it's optimized for responsiveness.

Digging Deeper: Why are Oppia Tests Flaky?

Let's be real, guys, test flakiness is one of the most annoying challenges in any robust software project, and our Oppia CI pipeline is not immune. When tests fail intermittently without any actual code changes, it erodes trust in our continuous integration system and slows down our ability to ship new features for story and chapter management. This specific instance, an E2E Acceptance CI failure related to topic manager operations, gives us a prime opportunity to understand the deeper reasons behind why our tests might be acting up. Often, flakiness isn't a single culprit but a combination of factors, especially when dealing with complex web applications like Oppia and its various modules. We need to consider everything from environmental instability to subtle timing differences that our automated tests might not be robust enough to handle. The fact that this particular failure occurred on mobile devices is a huge clue. Mobile environments introduce a whole new set of variables: varying screen sizes, different browser rendering engines, touch interactions versus mouse clicks, and potentially less powerful hardware compared to a desktop setup. These differences can amplify existing timing issues or expose new ones that aren't apparent on a desktop run. For instance, an element that loads quickly and is always clickable on a desktop might experience a slight delay or a rendering glitch on a mobile emulator, leading to our TimeoutError. The Cannot read properties of undefined (reading 'getStory') error also hints at race conditions, where the sequence of operations in the test doesn't perfectly match the application's readiness state. If our test tries to access a story property before the asynchronous data fetch is complete, boom, failure. This kind of interaction between test speed and application loading state is a classic source of flakiness.

Another significant contributor to test flakiness can be the test environment itself. Are our CI servers consistent in their performance? Are there network fluctuations, even minor ones, that could impact asset loading times? Is the Firebase emulator or the GAE development server consistently spinning up in the same amount of time, or are there variations that introduce timing discrepancies? In a complex setup like Oppia's CI, with multiple services like Datastore, Redis, Elasticsearch, and Firebase emulators running simultaneously, the startup sequence and inter-service communication can introduce delays that are hard to predict. This can lead to scenarios where a test passes 99 times but fails on the 100th due to a microsecond difference in when a resource becomes available. Furthermore, the very nature of E2E tests, which interact with the entire application stack, makes them inherently more susceptible to flakiness than unit tests. They touch the database, the backend logic, the front-end rendering, and network layers. Any instability in any of these layers can ripple up and cause an E2E test to fail. When we see failures like an element not being found or data being undefined, it forces us to re-evaluate our assumptions about how quickly and reliably our application components become ready for interaction. Understanding these deeper causes is the first step towards building more resilient tests and a more dependable Oppia CI pipeline, ensuring that our story and chapter management features are truly stable across all platforms. We need to arm ourselves with better debugging tools and more thoughtful test design to combat this persistent enemy of software development.

Mobile-Specific Challenges

When it comes to mobile testing, particularly for E2E Acceptance tests in the Oppia CI pipeline, we face a unique set of challenges that can significantly contribute to flakiness. Unlike desktop environments, mobile devices often have varying screen sizes, resolutions, and typically, less processing power. This means that UI elements might render differently, or take longer to become interactive. For our story and chapter management tests, this can lead to scenarios where an element that's perfectly visible and clickable on a desktop browser might be off-screen, partially obscured, or simply not ready on a mobile emulator within the same timeframe. The TimeoutError we observed, where an element took too long to become clickable, is a classic symptom of these mobile-specific rendering and performance differences. Furthermore, touch interactions on mobile are fundamentally different from mouse clicks. While Puppeteer tries to abstract this, underlying browser differences in how events are dispatched and handled on touch-enabled views can introduce subtle discrepancies. Our tests need to be robust enough to handle these variations, possibly by employing different waiting strategies or element locators specifically for mobile views. Mobile environments can also be more susceptible to network latency, even in a simulated CI environment, impacting the speed at which data for stories and chapters is fetched and rendered. All these factors contribute to the flakiness of our Oppia CI tests and demand a tailored approach to debugging and remediation.

Environment & Timing Issues

Beyond mobile, general environment and timing issues are huge contributors to test flakiness within any continuous integration system, including Oppia's. Our CI environment, which spins up multiple backend services (like Datastore, Redis, Elasticsearch, and Firebase emulators) alongside the GAE development server, is a complex beast. The order and speed at which these services become fully operational can vary slightly from one CI run to the next. This can introduce race conditions where a front-end test for story and chapter management tries to fetch data before the backend emulator is fully warmed up or before the data has been seeded correctly. The Cannot read properties of undefined (reading 'getStory') error is a strong indicator of such a race condition, where the application code (and thus the test expecting it) assumes data is present when it might not be due to a subtle delay in the environment. Similarly, shared resources on CI machines, network fluctuations, or even the underlying virtualization layer can introduce small, intermittent delays that lead to TimeoutErrors or elements not being ready for interaction. To combat these Oppia CI failures, we need to ensure our CI environment is as stable and predictable as possible. This might involve more explicit waits for service readiness during setup, adding retry mechanisms to our tests for transient failures, or ensuring that our application's data loading mechanisms are more resilient to network or backend delays. Ultimately, reducing flakiness means reducing the variance in our testing environment and making our tests more tolerant of the inherent complexities of distributed systems.

Our Action Plan: Tackling Oppia's Flaky Story/Chapter Tests

Alright, folks, it’s time to move from diagnosis to action! Tackling Oppia's flaky story/chapter tests is crucial for maintaining a high-quality, reliable Oppia CI pipeline. We've identified the root causes, from undefined story data to elements that refuse to be clickable on mobile, and now we need to put together a solid plan. Our primary goal is to enhance the stability and robustness of our E2E Acceptance tests that cover story and chapter management. This isn't just about patching a single failure; it's about building a more resilient testing framework that can withstand the dynamic nature of web applications and diverse testing environments, especially mobile. We need to implement strategies that proactively address race conditions, improve element interaction, and refine our error handling, ensuring that our CI system provides accurate feedback on the health of our codebase. By making these improvements, we'll not only fix the current flakiness but also prevent similar issues from cropping up in the future, allowing our development team to iterate faster and with greater confidence in the quality of new features. This action plan will focus on three key areas: refining how our tests wait for elements, bolstering the application's error handling and state management, and optimizing our CI rerun strategies to reduce false positives. Each step is designed to make our continuous integration process more reliable and trustworthy, ultimately benefiting every Oppia contributor and user. We're committed to making sure that managing stories and chapters in Oppia is a smooth experience, and our tests should reflect that commitment with unwavering consistency. Let’s dive into the specifics of how we're going to harden our test suite and make Oppia CI a beacon of stability.

Enhancing Element Interaction Waits

First up, let's talk about those stubborn elements that refuse to be clickable, causing our dreaded TimeoutError in Oppia CI. To combat this flakiness in story and chapter management tests, we need to significantly enhance our element interaction waits. Simply waiting for an element to be