package beaform.utilities;

import static org.junit.Assert.assertTrue;

import org.junit.Test;

public class SystemTimeTest {

	@Test
	public void testDefaultTimeSource() {
		final long start = System.currentTimeMillis();
		final long tested = SystemTime.getAsLong();
		final long end = System.currentTimeMillis();

		assertTrue("The tested value is not between the given arguments", isBetween(start, end, tested));
	}

	private boolean isBetween(long boundary1, long boundary2, long tested) {
		long upper, lower;

		if (boundary1 <= boundary2) {
			lower = boundary1;
			upper = boundary2;
		}
		else {
			lower = boundary2;
			upper = boundary1;
		}

		return (lower <= tested) && (tested <= upper);
	}

}

package beaform.utilities;

import static org.junit.Assert.assertTrue;

import org.junit.Test;

public class SystemTimeTest {

	@Test
	public void testDefaultTimeSource() {
		final long start = System.currentTimeMillis();
		final long tested = SystemTime.getAsLong();
		final long end = System.currentTimeMillis();

		assertBetween("The tested value is not between the given arguments", start, end, tested);
	}

	private void assertBetween(String message, long boundary1, long boundary2, long tested) {
		long upper, lower;

		if (boundary1 <= boundary2) {
			lower = boundary1;
			upper = boundary2;
		}
		else {
			lower = boundary2;
			upper = boundary1;
		}

		assertTrue(message, (lower <= tested) && (tested <= upper));
	}

}

--- 
+++ 
@@ -12,10 +12,10 @@
 		final long tested = SystemTime.getAsLong();
 		final long end = System.currentTimeMillis();
 
-		assertBetween("The tested value is not between the given arguments", start, end, tested);
+		assertTrue("The tested value is not between the given arguments", isBetween(start, end, tested));
 	}
 
-	private void assertBetween(String message, long boundary1, long boundary2, long tested) {
+	private boolean isBetween(long boundary1, long boundary2, long tested) {
 		long upper, lower;
 
 		if (boundary1 <= boundary2) {
@@ -27,7 +27,7 @@
 			upper = boundary1;
 		}
 
-		assertTrue(message, (lower <= tested) && (tested <= upper));
+		return (lower <= tested) && (tested <= upper);
 	}
 
 }
Move the actual assertion to the test
