Add tests for Lab model

What does this mr do?

This MR adds tests for the Lab model

src/test/java/nl/tudelft/ewi/queue/model/LabTest.java

@@ -593,4 +593,20 @@ public class LabTest {
 		assertThat(tempLab.needsJitsiLink(user)).isFalse();
 	}
 
+	@Test
+	public void requestByEmpty() {
+		Lab tempLab = new Lab();
+		assertThat(tempLab.requestsBy(user).size()).isEqualTo(0);
+	}
+
+	@Test
+	@Transactional
+	public void requestByNonEmpty() {
+		Lab tempLab = new Lab();
+		Request r1 = new Request(user, lab.getAssignments().get(0), lab.getRooms().get(0),
+				lab.getAllowedRequestTypes().get(0), "", lab);
+		tempLab.setRequests(Collections.singletonList(r1));
+		assertThat(tempLab.requestsBy(user).contains(r1)).isTrue();
+	}
+
 }