### Question:
EnvironmentValueProvider extends AbstractValueProvider { @Override protected String getValue(String key) { String value = System.getProperty(key); return (value != null) ? value : System.getenv(key); }    }### Answer:
@Test public void getValue() { System.setProperty("test", "yeah"); assertThat(provider.getValue("test"), equalTo("yeah")); }
@Test public void getValue_notDefined() { System.clearProperty("test"); assertThat(provider.getValue("test"), nullValue()); }