additional unit tests

Author: Lee Rhodes

src/main/java/com/yahoo/sketches/memory/MemoryMappedFile.java

@@ -124,7 +124,7 @@ public boolean isLoaded() {
                     String.format("Encountered %s exception while loading", e.getClass()));
         }
     }
-
+    
     /**
      * Forces any changes made to this content to be written to the storage device
      * containing the mapped file.
@@ -201,7 +201,7 @@ private void unmap() throws RuntimeException {
         }
     }
 
-    private static int pageCount(int ps, long length) {
+    static final int pageCount(int ps, long length) {
         long s = 1;
         while (s * ps < length) {
             s++;
@@ -224,7 +224,8 @@ private void createDummyMbbInstance() throws RuntimeException {
                     null,
                     null);
         } catch (Exception e) {
-            throw new RuntimeException(e);
+            throw new RuntimeException(
+                "Could not create Dummy MappedByteBuffer instance: " + e.getClass());
         }
     }
 

src/test/java/com/yahoo/sketches/memory/MemoryMappedFileTest.java

@@ -34,7 +34,7 @@ public void testIllegalArgumentException() throws Exception {
     File file = new File(getClass().getClassLoader().getResource("memory_mapped.txt").getFile());
     try {
       new MemoryMappedFile(file, -1, Integer.MAX_VALUE);
-      fail("Failed: testIllegalArgumentException: Pos was negative.");
+      fail("Failed: testIllegalArgumentException: Position was negative.");
     } catch (Exception e) {
       // Expected;
     }
@@ -47,7 +47,7 @@ public void testIllegalArgumentException() throws Exception {
     }
 
     try {
-      new MemoryMappedFile(file, 1, -2);
+      new MemoryMappedFile(file, Long.MAX_VALUE, 2);
       fail("Failed: testIllegalArgumentException: Sum of position + size is negative.");
     } catch (Exception e) {
       // Expected;
@@ -64,6 +64,7 @@ public void testMemoryMapAndFree() {
       assertEquals(memCapacity, mmf.getCapacity());
       mmf.freeMemory();
       assertEquals(0L, mmf.getCapacity());
+      assertEquals(MemoryMappedFile.pageCount(1, 16), 16); //check pageCounter
     } catch (Exception e) {
       fail("Failed: testMemoryMapAndFree()");
     }
@@ -186,6 +187,12 @@ public void testForce() throws Exception {
     }
   }
 
+  @Test
+  public void checkPassThrough() {
+    NativeMemory mem = new AllocMemory(1024L);
+    mem.freeMemory();
+  }
+  
   @SuppressWarnings("resource")
   private static File createFile(String fileName, String text) throws FileNotFoundException {
     File file = new File(fileName);