diff --git a/autotests/kformattest.cpp b/autotests/kformattest.cpp
--- a/autotests/kformattest.cpp
+++ b/autotests/kformattest.cpp
@@ -23,10 +23,11 @@
 
 #include "kformattest.h"
 
-#include <QtTest>
-
 #include "kformat.h"
 
+#include <QCoreApplication>
+#include <QtTest>
+
 void KFormatTest::formatByteSize()
 {
     QLocale locale(QLocale::c());
@@ -290,8 +291,8 @@
 {
     KFormat format(QLocale::c());
 
-    QCOMPARE(format.formatDecimalDuration(10), QStringLiteral("10 millisecond(s)"));
-    QCOMPARE(format.formatDecimalDuration(10, 3), QStringLiteral("10 millisecond(s)"));
+    QCOMPARE(format.formatDecimalDuration(10), QCoreApplication::translate("KFormat", "%n millisecond(s)", nullptr, 10));
+    QCOMPARE(format.formatDecimalDuration(10, 3), QCoreApplication::translate("KFormat", "%n millisecond(s)", nullptr, 10));
     QCOMPARE(format.formatDecimalDuration(1 * MSecsInSecond + 10), QStringLiteral("1.01 seconds"));
     QCOMPARE(format.formatDecimalDuration(1 * MSecsInSecond + 1, 3), QStringLiteral("1.001 seconds"));
     QCOMPARE(format.formatDecimalDuration(1 * MSecsInMinute + 10 * MSecsInSecond), QStringLiteral("1.17 minutes"));
@@ -306,22 +307,31 @@
 {
     KFormat format(QLocale::c());
 
-    QCOMPARE(format.formatSpelloutDuration(1000), QStringLiteral("1 second(s)"));
-    QCOMPARE(format.formatSpelloutDuration(5000), QStringLiteral("5 second(s)"));
-    QCOMPARE(format.formatSpelloutDuration(60000), QStringLiteral("1 minute(s)"));
-    QCOMPARE(format.formatSpelloutDuration(300000), QStringLiteral("5 minute(s)"));
-    QCOMPARE(format.formatSpelloutDuration(3600000), QStringLiteral("1 hour(s)"));
-    QCOMPARE(format.formatSpelloutDuration(18000000), QStringLiteral("5 hour(s)"));
-    QCOMPARE(format.formatSpelloutDuration(75000), QStringLiteral("1 minute(s) and 15 second(s)"));
+    QCOMPARE(format.formatSpelloutDuration(1000), QCoreApplication::translate("KFormat", "%n second(s)",  nullptr, 1));
+    QCOMPARE(format.formatSpelloutDuration(5000), QCoreApplication::translate("KFormat", "%n second(s)",  nullptr, 5));
+    QCOMPARE(format.formatSpelloutDuration(60000), QCoreApplication::translate("KFormat", "%n minute(s)", nullptr, 1));
+    QCOMPARE(format.formatSpelloutDuration(300000), QCoreApplication::translate("KFormat", "%n minute(s)", nullptr, 5));
+    QCOMPARE(format.formatSpelloutDuration(3600000), QCoreApplication::translate("KFormat", "%n hour(s)", nullptr, 1));
+    QCOMPARE(format.formatSpelloutDuration(18000000), QCoreApplication::translate("KFormat", "%n hour(s)", nullptr, 5));
+
+    QString s = QCoreApplication::translate("KFormat", "%1 and %2").arg(
+                    QCoreApplication::translate("KFormat", "%n minute(s)", nullptr, 1),
+                    QCoreApplication::translate("KFormat", "%n second(s)", nullptr, 15));
+
+    QCOMPARE(format.formatSpelloutDuration(75000), s);
     // Problematic case #1 (there is a reference to this case on kformat.cpp)
-    QCOMPARE(format.formatSpelloutDuration(119999), QStringLiteral("2 minute(s)"));
+    QCOMPARE(format.formatSpelloutDuration(119999), QCoreApplication::translate("KFormat", "%n minute(s)", nullptr, 2));
     // This case is strictly 2 hours, 15 minutes and 59 seconds. However, since the range is
     // pretty high between hours and seconds, formatSpelloutDuration always omits seconds when there
     // are hours in scene.
-    QCOMPARE(format.formatSpelloutDuration(8159000), QStringLiteral("2 hour(s) and 15 minute(s)"));
+    s = QCoreApplication::translate("KFormat", "%1 and %2").arg(
+            QCoreApplication::translate("KFormat", "%n hour(s)", nullptr, 2),
+            QCoreApplication::translate("KFormat", "%n minute(s)", nullptr, 15));
+
+    QCOMPARE(format.formatSpelloutDuration(8159000), s);
     // This case is strictly 1 hour and 10 seconds. For the same reason, formatSpelloutDuration
     // detects that 10 seconds is just garbage compared to 1 hour, and omits it on the result.
-    QCOMPARE(format.formatSpelloutDuration(3610000), QStringLiteral("1 hour(s)"));
+    QCOMPARE(format.formatSpelloutDuration(3610000), QCoreApplication::translate("KFormat", "%n hour(s)", nullptr, 1));
 }
 
 void KFormatTest::formatRelativeDate()