Tests: make max size and size on disk test easier to maintain

Instead of asserting some very specific sizes and messages that are not
really of importance, ensure the APIs fulfill reasonable expectations.

Author: greenrobot-team

tests/objectbox-java-test/src/test/java/io/objectbox/BoxStoreBuilderTest.java

@@ -261,31 +261,31 @@ public void maxSize_invalidValues_throw() {
     public void maxFileSize() {
         assumeFalse(IN_MEMORY); // no max size support for in-memory
 
+        // To avoid frequently changing the limit choose one high enough to insert at least one object successfully,
+        // then keep inserting until the limit is hit.
         builder = createBoxStoreBuilder(null);
-        // The empty data.mdb file is around 12 KB, but creating will fail also if slightly above that
-        builder.maxSizeInKByte(15);
-        DbFullException couldNotPut = assertThrows(
-                DbFullException.class,
-                () -> builder.build()
-        );
-        assertEquals("Could not put", couldNotPut.getMessage());
-
-        builder.maxSizeInKByte(30); // Empty file is around 12 KB, object below adds about 8 KB each.
+        builder.maxSizeInKByte(150);
         store = builder.build();
-        putTestEntity(LONG_STRING, 1);
-        TestEntity testEntity2 = createTestEntity(LONG_STRING, 2);
-        DbFullException dbFullException = assertThrows(
-                DbFullException.class,
-                () -> getTestEntityBox().put(testEntity2)
-        );
-        assertEquals("Could not commit tx", dbFullException.getMessage());
 
-        // Re-open with larger size.
+        putTestEntity(LONG_STRING, 1); // Should work
+
+        boolean dbFullExceptionThrown = false;
+        for (int i = 2; i < 1000; i++) {
+            TestEntity testEntity = createTestEntity(LONG_STRING, i);
+            try {
+                getTestEntityBox().put(testEntity);
+            } catch (DbFullException e) {
+                dbFullExceptionThrown = true;
+                break;
+            }
+        }
+        assertTrue("DbFullException was not thrown",  dbFullExceptionThrown);
+
+        // Check re-opening with larger size allows to insert again
         store.close();
-        builder.maxSizeInKByte(40);
+        builder.maxSizeInKByte(200);
         store = builder.build();
-        testEntity2.setId(0); // Clear ID of object that failed to put.
-        getTestEntityBox().put(testEntity2);
+        getTestEntityBox().put(createTestEntity(LONG_STRING, 1000));
     }
 
     @Test

tests/objectbox-java-test/src/test/java/io/objectbox/BoxStoreTest.java

@@ -309,13 +309,20 @@ private Callable<String> createTestCallable(final int[] countHolder) {
     @Test
     public void testSizeOnDisk() {
         // Note: initial database does have a non-zero (file) size.
+        @SuppressWarnings("deprecation")
         long legacySizeOnDisk = store.sizeOnDisk();
         assertTrue(legacySizeOnDisk > 0);
 
         assertTrue(store.getDbSize() > 0);
 
         long sizeOnDisk = store.getDbSizeOnDisk();
-        assertEquals(IN_MEMORY ? 0 : 12288, sizeOnDisk);
+        // Check the file size is at least a reasonable value
+        assertTrue("Size is not reasonable", IN_MEMORY ? sizeOnDisk == 0 : sizeOnDisk > 10000 /* 10 KB */);
+
+        // Check the file size increases after inserting
+        putTestEntities(10);
+        long sizeOnDiskAfterPut = store.getDbSizeOnDisk();
+        assertTrue("Size did not increase", IN_MEMORY ? sizeOnDiskAfterPut == 0 : sizeOnDiskAfterPut > sizeOnDisk);
     }
 
     @Test