@Override
    String getProperty(String key) {
        String checkedKey = checkPropertyName(key);
        if (checkedKey == null) {
            final String upperCaseKey = key.toUpperCase();
            if (!upperCaseKey.equals(key)) {
                checkedKey = checkPropertyName(upperCaseKey);
            }
        }
        if (checkedKey == null) {
            return null;
        }
        return env.get(checkedKey);
    }
@Test
    void testGetEnvForUpperCaseKeyWithHyphen() {
        assertEquals("value4", systemEnvPropertySource.getProperty("TEST-CASE-4"));
    }