diff --git a/Source/Tests/mmap.cpp b/Source/Tests/mmap.cpp
index b683a340..c2d267b4 100644
--- a/Source/Tests/mmap.cpp
+++ b/Source/Tests/mmap.cpp
@@ -22,19 +22,30 @@ class MMapTest : public CppUnit::TestFixture {
 
 public:
   void testMMapFile() {
+    size_t i;
     const int BUF_SIZE = 50000; // 50MB
 
+    // resize
+
     MMapFile mmap;
     mmap.resize(BUF_SIZE);
     CPPUNIT_ASSERT_EQUAL( BUF_SIZE, mmap.getsize() );
 
-    void *buf = mmap.get(0, BUF_SIZE);
-    memset(buf, 0x85, BUF_SIZE);
+    // set content
+
+    char *buf = (char *) mmap.get(0, BUF_SIZE);
+
+    for (i = 0; i < BUF_SIZE; i++) {
+      buf[i] = i % 256;
+    }
+
     mmap.release();
 
+    // test content and get(), getmore()
+
     srand(time(NULL));
 
-    for (size_t i = 0; i < 100; i++) {
+    for (i = 0; i < 100; i++) {
       int offset1 = rand() % BUF_SIZE;
       int size1 = rand() % (BUF_SIZE - offset1);
       char *p1 = (char *) mmap.get(offset1, size1);
@@ -43,9 +54,14 @@ public:
       int size2 = rand() % (BUF_SIZE - offset2);
       char *p2 = (char *) mmap.getmore(offset2, size2);
 
-      int minsize = min(size1, size2);
-      for (int j = 0; j < minsize; j++) {
-        CPPUNIT_ASSERT_EQUAL( p1[j], p2[j] );
+      int j;
+
+      for (j = 0; j < size1; j++) {
+        CPPUNIT_ASSERT_EQUAL( p1[j], char((offset1 + j) % 256) );
+      }
+
+      for (j = 0; j < size2; j++) {
+        CPPUNIT_ASSERT_EQUAL( p2[j], char((offset2 + j) % 256) );
       }
 
       mmap.release();