Common Mobile Bugs — Mobile App Testing | Sabaoon Academy

Experience teaches you where bugs hide. These are the most frequent mobile-specific bugs that testers encounter — learn to look for them proactively.

Crash Bugs

Out of Memory (OOM)

The app uses more memory than the OS allows and gets killed.

How to find it:

Open the app, navigate through many screens without going back
Load large images or long lists
Switch between the app and other memory-heavy apps
Leave the app running for extended periods

Bug report tip: Include the device model and RAM. A crash on a 3GB device that works on 8GB is an OOM issue.

Null Pointer / Undefined

The app tries to access data that doesn't exist yet.

Common triggers:

Navigating to a detail screen before data loads
Deep linking directly to a screen that expects prior data
Returning from background after data was garbage collected
Rotating the screen during an API call

Unhandled Exceptions

The app doesn't catch errors from APIs, permissions, or hardware.

Test by:

Denying every permission and using the feature anyway
Sending malformed deep links
Interrupting operations mid-way (force close during save)

UI Bugs

Keyboard Overlap

The virtual keyboard covers the input field the user is typing in.

How to test:

Tap every input field on every screen
Check that the view scrolls to keep the active field visible
Test with different keyboard sizes (default, autocomplete bar, third-party keyboards)

Layout Breaking on Small Screens

Designs built for iPhone 15 may break on iPhone SE.

What to look for:

Text overlapping other elements
Buttons pushed off-screen
Horizontal scrolling where there shouldn't be any
Truncated labels with no tooltip or expansion

Dark Mode Issues

Bug	Example
Invisible text	Dark text on dark background
Hard-coded colors	White background ignores dark mode
Image backgrounds	Logo has white background that doesn't adapt
Status bar	Dark text on dark status bar
Third-party components	WebViews or SDK UIs that ignore dark mode

Test by: Toggling dark mode on and off on every screen.

Orientation Bugs

Content disappears after rotation
Scroll position resets on rotation
Modal dialogs get mispositioned in landscape
Video player doesn't adapt to orientation change

Data Bugs

Data Not Persisting

User fills a form, switches to another app, comes back — form is empty
Settings reset after app update
Completed onboarding shows again after reinstall

Sync Issues

Data created offline duplicates when synced
Conflicts when the same item is edited on two devices
Stale data shown after sync completes (cache not invalidated)

Date and Timezone Bugs

Events show at wrong time for users in different timezones
"Today" filter shows wrong results near midnight
Date of birth field off by one day (timezone conversion)

Network Bugs

Loading States Missing

The screen shows nothing while data loads. Users think the app is broken.

Every API-dependent screen should have:

Loading skeleton or spinner
Error state with retry button
Empty state ("No items yet")

Timeout Handling

App hangs indefinitely on slow networks
No timeout — spinner spins forever
Timeout too aggressive — fails on 3G networks

Retry Logic

Failed requests don't retry automatically
Retry creates duplicate data (payment charged twice)
No exponential backoff — hammers the server

Permission Bugs

Scenario	Expected
Camera permission denied	Show explanation, link to settings
Location denied, then granted in settings	App picks up new permission without restart
Notification permission denied	App works without notifications, no crash
"Don't ask again" selected	Direct user to system settings
Permission revoked while app is open	Graceful degradation, not crash

Installation and Update Bugs

Fresh Install

Onboarding flow works correctly
Default settings are sensible
No leftover data from previous installs

App Update

User data survives the update
Database migrations run correctly
New features are introduced gracefully
No force-close after update

Uninstall

All app data is removed
Background services stop
No orphaned notifications

Interruption Bugs

Test what happens when the app is interrupted:

Interruption	What to Check
Incoming phone call	App pauses gracefully, resumes correctly
Push notification tapped	App navigates to correct screen
Low battery warning	No data loss
Alarm goes off	App state preserved
Screen lock/unlock	Session still valid
App switcher (recent apps)	Screenshot in app switcher is correct (no sensitive data)
Split screen / picture-in-picture	App adapts or gracefully declines

Bug Hunting Checklist

Use this checklist when testing any mobile screen: