@Test
    @SuppressWarnings("PMD.JUnitTestsShouldIncludeAssert") // is done in called test method
    public void allNone() {
        assertSingle(c -> c.setDifficulty(0f), null, true);
        assertSingle(c -> c.setDifficulty(0f), f -> f.setMinMaxRange(null, 5f), true);
        assertSingle(c -> c.setDifficulty(0f), f -> f.setMinMaxRange(1f, 5f), false);
        assertSingle(c -> c.setDifficulty(0f), f -> f.setMinMaxRange(1.5f, 5f), false);
    }
This class tests the number range filters, using DIFFICULTY filter as an example
main/src/androidTest/java/cgeo/geocaching/filters/NumberRangeGeocacheFilterTest.java