diff --git a/src/xlsx/xlsxformat.cpp b/src/xlsx/xlsxformat.cpp
index 60a068f..376264c 100755
--- a/src/xlsx/xlsxformat.cpp
+++ b/src/xlsx/xlsxformat.cpp
@@ -903,7 +903,7 @@ QByteArray Format::formatKey() const
         QByteArray key;
         QDataStream stream(&key, QIODevice::WriteOnly);
 
-        QHashIterator<int, QVariant> i(d->property);
+        QMapIterator<int, QVariant> i(d->property);
         while (i.hasNext()) {
             i.next();
             stream<<i.key()<<i.value();
@@ -1108,4 +1108,12 @@ QColor Format::colorProperty(int propertyId) const
     return qvariant_cast<QColor>(prop);
 }
 
+#ifndef QT_NO_DEBUG_STREAM
+QDebug operator<<(QDebug dbg, const Format &f)
+{
+    dbg.nospace() << "QXlsx::Format(" << f.d->property << ")";
+    return dbg.space();
+}
+#endif
+
 QT_END_NAMESPACE_XLSX
diff --git a/src/xlsx/xlsxformat.h b/src/xlsx/xlsxformat.h
index 639176f..843a0f0 100755
--- a/src/xlsx/xlsxformat.h
+++ b/src/xlsx/xlsxformat.h
@@ -237,6 +237,7 @@ private:
     friend class RichStringPrivate;
     friend class SharedStrings;
     friend class ::FormatTest;
+    friend Q_XLSX_EXPORT QDebug operator<<(QDebug, const Format &f);
 
     bool fontIndexValid() const;
     int fontIndex() const;
@@ -274,6 +275,10 @@ private:
     QExplicitlySharedDataPointer<FormatPrivate> d;
 };
 
+#ifndef QT_NO_DEBUG_STREAM
+Q_XLSX_EXPORT QDebug operator<<(QDebug dbg, const Format &f);
+#endif
+
 QT_END_NAMESPACE_XLSX
 
 #endif // QXLSX_FORMAT_H
diff --git a/src/xlsx/xlsxformat_p.h b/src/xlsx/xlsxformat_p.h
index f7d5631..d4434d4 100644
--- a/src/xlsx/xlsxformat_p.h
+++ b/src/xlsx/xlsxformat_p.h
@@ -26,7 +26,7 @@
 #define XLSXFORMAT_P_H
 #include "xlsxformat.h"
 #include <QSharedData>
-#include <QHash>
+#include <QMap>
 
 namespace QXlsx {
 
@@ -148,7 +148,7 @@ public:
 
     int theme;
 
-    QHash<int, QVariant> property;
+    QMap<int, QVariant> property;
 };
 
 }
diff --git a/tests/auto/document/tst_documenttest.cpp b/tests/auto/document/tst_documenttest.cpp
index 5eba30b..53e1233 100644
--- a/tests/auto/document/tst_documenttest.cpp
+++ b/tests/auto/document/tst_documenttest.cpp
@@ -29,20 +29,25 @@ DocumentTest::DocumentTest()
 
 void DocumentTest::testDocumentProperty()
 {
+    QBuffer device;
+    device.open(QIODevice::WriteOnly);
+
     Document xlsx1;
     xlsx1.setDocumentProperty("creator", "Debao");
     xlsx1.setDocumentProperty("company", "Test");
-    xlsx1.saveAs("test.xlsx");
+    xlsx1.saveAs(&device);
 
-    Document xlsx2("test.xlsx");
+    device.open(QIODevice::ReadOnly);
+    Document xlsx2(&device);
     QCOMPARE(xlsx2.documentProperty("creator"), QString("Debao"));
     QCOMPARE(xlsx2.documentProperty("company"), QString("Test"));
-
-    QFile::remove("test.xlsx");
 }
 
 void DocumentTest::testReadWriteString()
 {
+    QBuffer device;
+    device.open(QIODevice::WriteOnly);
+
     Document xlsx1;
     xlsx1.write("A1", "Hello Qt!");
     Format format;
@@ -50,24 +55,26 @@ void DocumentTest::testReadWriteString()
     format.setBorderStyle(Format::BorderDashDotDot);
     format.setFillPattern(Format::PatternSolid);
     xlsx1.write("A2", "Hello Qt again!", format);
-    xlsx1.saveAs("test.xlsx");
+    xlsx1.saveAs(&device);
 
-    Document xlsx2("test.xlsx");
+    device.open(QIODevice::ReadOnly);
+    Document xlsx2(&device);
     QCOMPARE(xlsx2.cellAt("A1")->dataType(), Cell::String);
     QCOMPARE(xlsx2.cellAt("A1")->value().toString(), QString("Hello Qt!"));
     QCOMPARE(xlsx2.cellAt("A2")->dataType(), Cell::String);
     QCOMPARE(xlsx2.cellAt("A2")->value().toString(), QString("Hello Qt again!"));
-    QVERIFY(xlsx2.cellAt("A2")->format().isValid());
-    QCOMPARE(xlsx2.cellAt("A2")->format().fontColor(), format.fontColor());
-    QCOMPARE(xlsx2.cellAt("A2")->format().leftBorderStyle(), format.leftBorderStyle());
-    QCOMPARE(xlsx2.cellAt("A2")->format().fillPattern(), format.fillPattern());
-//    QCOMPARE(xlsx2.cellAt("A2")->format(), format);
-
-    QFile::remove("test.xlsx");
+    Format format2 = xlsx2.cellAt("A2")->format();
+    QVERIFY(format2.isValid());
+//    qDebug()<<format2;
+//    qDebug()<<format;
+    QCOMPARE(format2, format);
 }
 
 void DocumentTest::testReadWriteNumeric()
 {
+    QBuffer device;
+    device.open(QIODevice::WriteOnly);
+
     Document xlsx1;
     xlsx1.write("A1", 123);
     Format format;
@@ -76,21 +83,23 @@ void DocumentTest::testReadWriteNumeric()
     format.setFillPattern(Format::PatternSolid);
     format.setNumberFormatIndex(10);
     xlsx1.write("A2", 12345, format);
-    xlsx1.saveAs("test.xlsx");
+    xlsx1.saveAs(&device);
 
-    Document xlsx2("test.xlsx");
+    device.open(QIODevice::ReadOnly);
+    Document xlsx2(&device);
     QCOMPARE(xlsx2.cellAt("A1")->dataType(), Cell::Numeric);
     QCOMPARE(xlsx2.cellAt("A1")->value().toDouble(), 123.0);
     QCOMPARE(xlsx2.cellAt("A2")->dataType(), Cell::Numeric);
     QCOMPARE(xlsx2.cellAt("A2")->value().toDouble(), 12345.0);
     QVERIFY(xlsx2.cellAt("A2")->format().isValid());
     QCOMPARE(xlsx2.cellAt("A2")->format(), format);
-
-    QFile::remove("test.xlsx");
 }
 
 void DocumentTest::testReadWriteBool()
 {
+    QBuffer device;
+    device.open(QIODevice::WriteOnly);
+
     Document xlsx1;
     xlsx1.write("A1", true);
     Format format;
@@ -98,21 +107,23 @@ void DocumentTest::testReadWriteBool()
     format.setBorderStyle(Format::BorderDashDotDot);
     format.setFillPattern(Format::PatternSolid);
     xlsx1.write("A2", false, format);
-    xlsx1.saveAs("test.xlsx");
+    xlsx1.saveAs(&device);
 
-    Document xlsx2("test.xlsx");
+    device.open(QIODevice::ReadOnly);
+    Document xlsx2(&device);
     QCOMPARE(xlsx2.cellAt("A1")->dataType(), Cell::Boolean);
     QCOMPARE(xlsx2.cellAt("A1")->value().toBool(), true);
     QCOMPARE(xlsx2.cellAt("A2")->dataType(), Cell::Boolean);
     QCOMPARE(xlsx2.cellAt("A2")->value().toBool(), false);
     QVERIFY(xlsx2.cellAt("A2")->format().isValid());
     QCOMPARE(xlsx2.cellAt("A2")->format(), format);
-
-    QFile::remove("test.xlsx");
 }
 
 void DocumentTest::testReadWriteBlank()
 {
+    QBuffer device;
+    device.open(QIODevice::WriteOnly);
+
     Document xlsx1;
     xlsx1.write("A1", QVariant());
     Format format;
@@ -120,9 +131,10 @@ void DocumentTest::testReadWriteBlank()
     format.setBorderStyle(Format::BorderDashDotDot);
     format.setFillPattern(Format::PatternSolid);
     xlsx1.write("A2", QVariant(), format);
-    xlsx1.saveAs("test.xlsx");
+    xlsx1.saveAs(&device);
 
-    Document xlsx2("test.xlsx");
+    device.open(QIODevice::ReadOnly);
+    Document xlsx2(&device);
     QVERIFY(xlsx2.cellAt("A1"));
     QCOMPARE(xlsx2.cellAt("A1")->dataType(), Cell::Blank);
     QVERIFY(!xlsx2.cellAt("A1")->value().isValid());
@@ -131,12 +143,13 @@ void DocumentTest::testReadWriteBlank()
     QVERIFY(!xlsx2.cellAt("A2")->value().isValid());
     QVERIFY(xlsx2.cellAt("A2")->format().isValid());
     QCOMPARE(xlsx2.cellAt("A2")->format(), format);
-
-    QFile::remove("test.xlsx");
 }
 
 void DocumentTest::testReadWriteFormula()
 {
+    QBuffer device;
+    device.open(QIODevice::WriteOnly);
+
     Document xlsx1;
     xlsx1.write("A1", "=11+22");
     Format format;
@@ -144,10 +157,11 @@ void DocumentTest::testReadWriteFormula()
     format.setBorderStyle(Format::BorderDashDotDot);
     format.setFillPattern(Format::PatternSolid);
     xlsx1.write("A2", "=22+33", format);
-    xlsx1.saveAs("test.xlsx");
+    xlsx1.saveAs(&device);
 
 
-    Document xlsx2("test.xlsx");
+    device.open(QIODevice::ReadOnly);
+    Document xlsx2(&device);
     QCOMPARE(xlsx2.cellAt("A1")->dataType(), Cell::Formula);
 //    QCOMPARE(xlsx2.cellAt("A1")->value().toDouble(), 0.0);
     QCOMPARE(xlsx2.cellAt("A1")->formula(), QStringLiteral("11+22"));
@@ -156,12 +170,13 @@ void DocumentTest::testReadWriteFormula()
     QCOMPARE(xlsx2.cellAt("A2")->formula(), QStringLiteral("22+33"));
     QVERIFY(xlsx2.cellAt("A2")->format().isValid());
     QCOMPARE(xlsx2.cellAt("A2")->format(), format);
-
-    QFile::remove("test.xlsx");
 }
 
 void DocumentTest::testReadWriteDateTime()
 {
+    QBuffer device;
+    device.open(QIODevice::WriteOnly);
+
     Document xlsx1;
     QDateTime dt(QDate(2012, 11, 12), QTime(6, 0), Qt::UTC);
 
@@ -177,10 +192,10 @@ void DocumentTest::testReadWriteDateTime()
     format3.setNumberFormat("dd/mm/yyyy");
     xlsx1.write("A3", dt, format3);
 
-    xlsx1.saveAs("test.xlsx");
-
-    Document xlsx2("test.xlsx");
+    xlsx1.saveAs(&device);
 
+    device.open(QIODevice::ReadOnly);
+    Document xlsx2(&device);
     QCOMPARE(xlsx2.cellAt("A1")->dataType(), Cell::Numeric);
     QCOMPARE(xlsx2.cellAt("A1")->isDateTime(), true);
     QCOMPARE(xlsx2.cellAt("A1")->dateTime(), dt);
@@ -195,9 +210,6 @@ void DocumentTest::testReadWriteDateTime()
     QCOMPARE(xlsx2.cellAt("A3")->isDateTime(), true);
     QCOMPARE(xlsx2.cellAt("A3")->dateTime(), dt);
     QCOMPARE(xlsx2.cellAt("A3")->format().numberFormat(), QString("dd/mm/yyyy"));
-
-    QFile::remove("test.xlsx");
-
 }
 
 QTEST_APPLESS_MAIN(DocumentTest)