Add oving 4

src/test/java/oving4/PartnerTest.java

@@ -0,0 +1,74 @@
+package oving4;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+public class PartnerTest {
+
+	private Partner p1;
+	private Partner p2;
+
+	@BeforeEach
+	public void setUp() {
+		p1 = new Partner("P1");
+		p2 = new Partner("P2");
+	}
+
+	@Test
+	@DisplayName("Check that the constructor initializes correctly")
+	public void testConstructor() {
+		assertNull(p1.getPartner());
+		assertNull(p2.getPartner());
+
+		assertThrows(IllegalArgumentException.class, () -> {
+			new Partner(null);
+		}, "Name cannot be null");
+	}
+
+	@Test
+	@DisplayName("Check that P1 and P2 are partners after p1.setPartner(p2)")
+	public void simplePartnership() {
+		assertNull(p1.getPartner());
+		assertNull(p2.getPartner());
+
+		p1.setPartner(p2);
+		assertEquals(p1.getPartner(), p2, "P1 should be partner to P2");
+		assertEquals(p2.getPartner(), p1, "P2 should be partner to P1");
+	}
+
+	@Test
+	@DisplayName("Check that one can split up a partnership")
+	public void partnershipWithDivorce() {
+		p1.setPartner(p2);
+		assertEquals(p1.getPartner(), p2, "P1 should be partner to P2");
+		assertEquals(p2.getPartner(), p1, "P2 should be partner to P1");
+
+		p1.setPartner(null);
+		assertNull(p1.getPartner());
+		assertNull(p2.getPartner());
+	}
+
+	@Test
+	@DisplayName("Check that combined breakup followed by the creation of a new partnership works")
+	public void swinger() {
+		Partner p3 = new Partner("P3");
+		Partner p4 = new Partner("P4");
+
+		p1.setPartner(p2);
+		p3.setPartner(p4);
+		assertEquals(p1.getPartner(), p2, "P1 should be the partner of P2");
+		assertEquals(p2.getPartner(), p1, "P2 should be the partner of P1");
+		assertEquals(p3.getPartner(), p4, "P3 should be the partner of P4");
+		assertEquals(p4.getPartner(), p3, "P4 should be the partner of P3");
+
+		p1.setPartner(p4);
+		assertEquals(p1.getPartner(), p4, "P4 should be the partner of P1");
+		assertEquals(p4.getPartner(), p1, "P1 should be the partner of P4");
+		assertNull(p2.getPartner());
+		assertNull(p3.getPartner());
+	}
+}