diff --git a/tests/devices/filestorage.js b/tests/devices/filestorage.js
index 7da0637c..b8bc3043 100755
--- a/tests/devices/filestorage.js
+++ b/tests/devices/filestorage.js
@@ -53,9 +53,9 @@ function assert_uint8array_equal(actual, expected)
     return true;
 }
 
-const db = new Map();
 function mock_indexeddb()
 {
+    const db = new Map();
     return {
         transaction(store_name, mode) {
             return {
@@ -81,42 +81,36 @@ function mock_indexeddb()
     };
 }
 
-// Oracle without chunking.
-const memory_file_storage = new MemoryFileStorage();
-
-// IUT with chunking.
-const indexeddb_file_storage = new IndexedDBFileStorage(mock_indexeddb());
-
-async function test_read(key, offset, count) // jshint ignore:line
+async function test_read(oracle, iut, key, offset, count) // jshint ignore:line
 {
-    const expected = await memory_file_storage.read(key, offset, count); // jshint ignore:line
-    const actual = await indexeddb_file_storage.read(key, offset, count); // jshint ignore:line
+    const expected = await oracle.read(key, offset, count); // jshint ignore:line
+    const actual = await iut.read(key, offset, count); // jshint ignore:line
     return assert_uint8array_equal(actual, expected);
 }
 
-async function test_with_file(key, file_data) // jshint ignore:line
+async function test_with_file(oracle, iut, key, file_data) // jshint ignore:line
 {
     console.log("Testing file with size: %d", file_data.length);
-    await memory_file_storage.set(key, file_data); // jshint ignore:line
-    await indexeddb_file_storage.set(key, file_data); // jshint ignore:line
+    await oracle.set(key, file_data); // jshint ignore:line
+    await iut.set(key, file_data); // jshint ignore:line
 
     // Some boundary values.
-    if(!await test_read(key, 0, 0)) return; // jshint ignore:line
-    if(!await test_read(key, 0, 1)) return; // jshint ignore:line
-    if(!await test_read(key, 0, 4096)) return; // jshint ignore:line
-    if(!await test_read(key, 0, 4097)) return; // jshint ignore:line
-    if(!await test_read(key, 4095, 2)) return; // jshint ignore:line
-    if(!await test_read(key, 4096, 1)) return; // jshint ignore:line
-    if(!await test_read(key, 4096, 4096)) return; // jshint ignore:line
-    if(!await test_read(key, 4097, 1)) return; // jshint ignore:line
-    if(!await test_read(key, 4097, 4095)) return; // jshint ignore:line
+    if(!await test_read(oracle, iut, key, 0, 0)) return; // jshint ignore:line
+    if(!await test_read(oracle, iut, key, 0, 1)) return; // jshint ignore:line
+    if(!await test_read(oracle, iut, key, 0, 4096)) return; // jshint ignore:line
+    if(!await test_read(oracle, iut, key, 0, 4097)) return; // jshint ignore:line
+    if(!await test_read(oracle, iut, key, 4095, 2)) return; // jshint ignore:line
+    if(!await test_read(oracle, iut, key, 4096, 1)) return; // jshint ignore:line
+    if(!await test_read(oracle, iut, key, 4096, 4096)) return; // jshint ignore:line
+    if(!await test_read(oracle, iut, key, 4097, 1)) return; // jshint ignore:line
+    if(!await test_read(oracle, iut, key, 4097, 4095)) return; // jshint ignore:line
 
     // Random ranges.
     for(let i = 0; i < NUMBER_OF_TESTREADS; i++)
     {
         const offset = Math.floor(Math.random() * MAX_TESTFILE_SIZE);
         const count = Math.floor(Math.random() * MAX_TESTFILE_SIZE);
-        const pass = await test_read(key, offset, count); // jshint ignore:line
+        const pass = await test_read(oracle, iut, key, offset, count); // jshint ignore:line
         if(!pass)
         {
             log_fail("Test case offset=%d, count=%d", offset, count);
@@ -129,17 +123,24 @@ async function test_with_file(key, file_data) // jshint ignore:line
 
 async function test_start() // jshint ignore:line
 {
-    if(!await test_with_file("empty", new Uint8Array(0))) return; // jshint ignore:line
-    if(!await test_with_file("single", new Uint8Array(1).map(v => Math.random() * 0xFF))) return; // jshint ignore:line
-    if(!await test_with_file("1block", new Uint8Array(4096).map(v => Math.random() * 0xFF))) return; // jshint ignore:line
+    // Test oracle without chunking.
+    const oracle = new MemoryFileStorage();
+
+    // Implementation under test with chunking.
+    const iut = new IndexedDBFileStorage(mock_indexeddb());
+
+    if(!await test_with_file(oracle, iut, "empty", new Uint8Array(0))) return; // jshint ignore:line
+    if(!await test_with_file(oracle, iut, "single", new Uint8Array(1).map(v => Math.random() * 0xFF))) return; // jshint ignore:line
+    if(!await test_with_file(oracle, iut, "1block", new Uint8Array(4096).map(v => Math.random() * 0xFF))) return; // jshint ignore:line
 
     for(let i = 0; i < NUMBER_OF_TESTFILES; i++)
     {
         const size = Math.floor(Math.random() * MAX_TESTFILE_SIZE);
         const file_data = new Uint8Array(size).map(v => Math.random() * 0xFF);
-        const pass = await test_with_file(i.toString(), file_data); // jshint ignore:line
+        const pass = await test_with_file(oracle, iut, i.toString(), file_data); // jshint ignore:line
         if(!pass) return;
     }
+
     log_pass("All tests passed!");
 }