tests: add Language qml test cases

Add tst_qPrefLanguage qml file to test C++ qml connection

Signed-off-by: Jan Iversen <jani@apache.org>

tests/tst_qPrefLanguage.qml

@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0
+import QtQuick 2.6
+import QtTest 1.2
+import org.subsurfacedivelog.mobile 1.0
+
+TestCase {
+	name: "qPrefLanguage"
+
+	SsrfLanguagePrefs {
+		id: tst
+	}
+
+	SsrfPrefs {
+		id: prefs
+	}
+
+	function test_variables() {
+		var x1 = tst.date_format
+		tst.date_format = "new date format"
+		compare(tst.date_format, "new date format")
+
+		var x2 = tst.date_format_override
+		tst.date_format_override = true
+		compare(tst.date_format_override, true)
+
+		var x3 = tst.date_format_short
+		tst.date_format_short = "new short format"
+		compare(tst.date_format_short, "new short format")
+
+		var x4 = tst.language
+		tst.language = "new lang format"
+		compare(tst.language, "new lang format")
+
+		var x5 = tst.lang_locale
+		tst.lang_locale = "new loc lang format"
+		compare(tst.lang_locale, "new loc lang format")
+
+		var x6 = tst.time_format
+		tst.time_format = "new time format"
+		compare(tst.time_format, "new time format")
+
+		var x7 = tst.time_format_override
+		tst.time_format_override = true
+		compare(tst.time_format_override, true)
+
+		var x8 = tst.use_system_language
+		tst.use_system_language = true
+		compare(tst.use_system_language, true)
+	}
+}