Android: Test investigating for RAM consumption - Heap and Heap Dump

The process of allocating new objects and removing the unused objects to make space for the new allocation is termed as Memory Management.  

Object Memory Management - Heap and Stack

Hearing the two terms Stack and Heap, can bring confusion in the memory management. Though I will not get in detail about each here, I will share briefly for what I have understood.  

The 'stack' memory is used for static memory allocation and 'heap' is used for dynamic allocation. For those allocated on the 'stack', they are stored directly to the memory and the allocation happens when the program is compiled. Whereas for those allocated on 'heap' have their memory allocated at the run time and the size of heap is limited by the virtual memory. Both the 'heap' and 'stack' are stored in RAM.

Shallow Heap and Retained Heap

Moving ahead, in 'heap' we will hear the words -- Shallow Heap and Retained Heap.

• Shallow heap -- is the amount memory consumed by one object. That is, the amount of memory allocated to store the object itself by not taking the reference objects into consideration. The shallow heap size of set of objects is the sum of shallow sizes all objects in the set.
• Retained heap -- is the amount memory consumed by all objects that are still alive by objects at the root of the retained set. The retained heap size of an object is, "shallow heap size" added with "shallow heap size of objects that are accessible directly or indirectly, only from this object".
• Retained set -- is the set of objects which will be removed by garbage collection when an object or multiple objects is garbage collected.

In other way, the shallow heap of an object is the size of object in the heap. The retained size of the same object is the amount of heap memory that is freed when this object is garbage collected.

From these two resources (1 and 2), I have understood the details of Shallow Heap and Retained Heap. I feel it is simple and well explained; I have been referring it since years.

Heap dump

It is a snapshot of the memory at a Java process at a given point of time. The dump will consist of Java objects and classes. The reference of memory for the objects and classes will be available in the dump taken. If the Garbage Collection occurs at time of obtaining the dump, then the obtained heap dump will have details and information about the remaining (existing & used, existing & unused) objects and classes.

The heap dump do not tell who created the object and where it was created. Based on type of heap dump, the information available in the dump will be as below.

1. Classes -- Classloader, name, super class, static fields
2. Objects -- Class, primitive value and references, fields
3. Thread Stacks and variables -- The information about call stack of threads at time of obtaining heap dump. The information about local variables and objects.
4. GC Roots -- The mentioning of objects which are reachable by JVM

Benefits of sharing the debug APK with tester

On knowing -- the myths around debug APK; what is debugging? and how tester can debug and be of help to programmer?, I tell about the benefits.  The programmer, product owner and team will benefit by sharing the debug APK to tester for testing. However, make sure you are in synchronous and mutual agreement with the tester if there is a 'concern' in sharing so.

"benefits" to programmer in sharing Debug APK to tester

Test investigating using log

With the debug APK the code written to print system messages, debug messages, and stack trace will print the information into the log.  While testing, tester can learn the logs to monitor -- what's happening within the device; what's happening to the app and what's happening in the environment where the device is. Won't this help to debug and investigate the problem or incident? The additional information shared by the tester apart from the incident won't it help programmer to the trigger or cause of the incident?

Test investigating with variables and breakpoints

The source code of app is available to tester and tester is using the debug app on her/his device or emulator. During this time tester can watch the variables, execution sequence and flows, knowing the stack details around the break points and analyze the code. This will help the tester to be stronger and get skilled each time. As a return, it comes back in testing to your product/app. Getting to frame level debugging and testing, wow! Is not that a value add?  If the tester need assistance to start here, giving few hours initially is a worth investment!

Tracking and testing for consumption and allocation

Yes, testing for allocations and use of HEAP. Further testing for network consumption, battery consumption, CPU consumption and UI performance. Is this not a value add in building high performance mobile app?

"limitation" with benefits in context of tester

As the benefit, there are also limitations in what a tester can do in context.  One such context is tester not having the source code of the app but has the debug APK.

Here, the tester might not be able to look into variables, stack values and test using the breakpoints. But, the tester can decompile the APK and work with compiled code with breakpoints and watch the execution flows. This is time consuming task and the task which can end abruptly if insertion of breakpoint and flow is paused incorrectly. Reporting the problem out of this observation is not suggested unless it is very sure that there is a problem.  But this not stop from testing for consumption and allocation by the app on the device.

As this, there can arise several context which yields the limitation. Figuring out how better the testability can be visualized and making use of it in testing, is the skill of tester.  Everyone in the team will have role to help tester to acquire and hone such skills.

"why" the delay in giving a debug APK to your tester?

If you are a programmer and product owner, then on knowing these benefits, yet if you are delaying to share a debug APK with tester, then there is a concern which needs to be addressed by project management.  This is what I learn.

If you are a tester and have come to know the value you can add from your testing, it will be a unfair to be quite and not asking for the debug APK.

"closing" thought with iOS and WP debug app

As with Android APK, the iOS and WP apps also have debug apps.  The benefit of it is quite similar. As well, there are additional benefits when testing in the respective programming environment with it's devices with the debug app.

Explore the benefits. Encourage the better and useful testing for the context of product.