A unit test to enforce max heap when running Android UT on the PC

2013's mobile devices come with 1-2GB RAM, yet Android still enforces a very small heap size of 24MB-64MB only (though it keeps increasing with time).

It's pretty easy to write an Android app that drains the heap. For example: Caching images w/o an LRU cache, reading whole files into memory instead of working with streams.

-- Your code will always use up as much memory as the system has (My spin on Parkinson's law).

I'm developing an Android app with a big UT suite that I run on Eclipse in the PC. I noticed that my default heap size is 256MB, huge compared to mobile, meaning my tests could pass on the PC, but still cause an OOME on an actual device.

So, I created MobileLikeSmallHeapDuringTestsEnforce, a new unit test to enforce a small heap size during Junit tests execution. Just make sure you throw it in to any test project you have and you're safe.

Created as a GitHubGist, you're welcome to make it better:

	import static org.junit.Assert.assertTrue;
	import org.junit.Test;
	public class MobileLikeSmallHeapDuringTestsEnforce {
	public static final long MB = 1024 * 1024;
	public static final long ANDROID_TYPICAL_MAX_HEAP_MB = 24;
	public static final String XMX_ARGUMENT = "-Xmx" + ANDROID_TYPICAL_MAX_HEAP_MB + "m";
	@Test
	public void assertHeapIsMobileLikeSmall() {
	long maxMemory = Runtime.getRuntime().maxMemory();
	assertTrue("Max heap is too high for mobile!\n" +
	"This JUnit test JVM heap max memory (" + maxMemory / MB + "MB) "
	+ "is higher than the max heap size on a typical Android device (" + ANDROID_TYPICAL_MAX_HEAP_MB + "MB).\n" +
	"Lowering max heap size will allow you to catch code flows that use too much memory.\n" +
	"To correct: Add " + XMX_ARGUMENT + " as a VM argument.\n" +
	"Correct in eclipse: menu > Run > Run Configuration... > Arguments tab > VM arguments > " + XMX_ARGUMENT,
	maxMemory <= ANDROID_TYPICAL_MAX_HEAP_MB * MB);
	}
	}

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