add olympic-medal-table corner case

src/final_assignment/task_2/tests/CornerCases.java

+package final_assignment.task_2.tests;
+
+import final_assignment.task_2.Assignment2TestBase;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+/**
+ * For small corner case tests
+ * please add the io file into data/corner_cases and add a new test method for more tests
+ */
+public class CornerCases extends Assignment2TestBase {
+    /**
+     * Tests if olympic-medal-table only lists nations which took part in some competition,
+     * but lists these which didn't win any medal
+     */
+    @Test
+    @DisplayName("medal-table")
+    void medalTable() {
+        testWithIOFile(getDataFolderDirectory() + "corner_cases/medal_table.io");
+    }
+}

src/final_assignment/task_2/tests/data/corner_cases/medal_table.io

+Tests if olympic-medal-table only lists nations which took part in some competition,
+but lists these which didn't win any medal
+> add-admin vorname;nachname;tester;123123123
+OK
+> login-admin tester;123123123
+OK
+> add-ioc-code 001;can;canada;2000
+OK
+> add-ioc-code 002;den;denmark;2000
+OK
+> add-olympic-sport fencing;fencing
+OK
+> add-athlete 0001;alex;edwin;canada;fencing;fencing
+OK
+> add-athlete 0002;benjamin;maria;denmark;fencing;fencing
+OK
+> add-competition 0001;2002;canada;fencing;fencing;0;0;0
+OK
+> olympic-medal-table
+(1,001,can,canada,0,0,0,0)