@Test
public void testMinimumValue() {

    assertEquals(0.0, g1.minimumValue(network), 0.0);
    assertEquals(0, g2.minimumValue(network, GENERATOR), 0.0);
    assertEquals(-100, g2.minimumValue(network, LOAD), 0.0);
    assertEquals(0, g4.minimumValue(network, GENERATOR), 0);
    assertEquals(-80, g4.minimumValue(network, LOAD), 0);
    assertEquals(20, g5.minimumValue(network, GENERATOR), 0);
    assertEquals(-100, g5.minimumValue(network, LOAD), 0);
}