[libcalamares] Test the spot-patch for Johannesburg

- Add a note about notation, degrees-minutes

src/libcalamares/locale/Tests.cpp

@@ -54,6 +54,7 @@ private Q_SLOTS:
     void testTZIterator();
     void testLocationLookup_data();
     void testLocationLookup();
+    void testLocationLookup2();
 };
 
 LocaleTests::LocaleTests() {}
@@ -423,6 +424,37 @@ LocaleTests::testLocationLookup()
     QCOMPARE( zone->zone(), name );
 }
 
+void
+LocaleTests::testLocationLookup2()
+{
+    // Official
+    // ZA      -2615+02800     Africa/Johannesburg
+    // Spot patch
+    //     "ZA -3230+02259 Africa/Johannesburg\n";
+
+    const CalamaresUtils::Locale::ZonesModel zones;
+    const auto* zone = zones.find( -26.15, 28.00 );
+    QCOMPARE( zone->zone(), QString( "Johannesburg" ) );
+    // The TZ data sources use minutes-and-seconds notation,
+    // so "2615" is 26 degrees, 15 minutes, and 15 minutes is
+    // one-quarter of a degree.
+    QCOMPARE( zone->latitude(), -26.25 );
+    QCOMPARE( zone->longitude(), 28.00 );
+
+    // Elsewhere in South Africa
+    const auto* altzone = zones.find( -32.0, 22.0 );
+    QCOMPARE( altzone, zone );  // same pointer
+    QCOMPARE( altzone->zone(), QString( "Johannesburg" ) );
+    QCOMPARE( altzone->latitude(), -26.25 );
+    QCOMPARE( altzone->longitude(), 28.00 );
+
+    altzone = zones.find( -29.0, 27.0 );
+    QCOMPARE( altzone->zone(), QString( "Maseru" ) );
+    // -2928, that's -29 and 28/60 of a degree, is almost half, but we don't want
+    //   to fall foul of variations in double-precision
+    QCOMPARE( trunc( altzone->latitude() * 1000.0 ), -29466 );
+}
+
 
 QTEST_GUILESS_MAIN( LocaleTests )