addEdge(graph2, "a", "b");
        addEdge(graph2, "b", "c");
        CycleDetectedException cde = assertThrows(CycleDetectedException.class, () -> addEdge(graph2, "c", "a"));
        List<String> cycle = cde.getCycle();
        assertNotNull(cycle, "Cycle should be not null");
        assertTrue(cycle.contains("a"), "Cycle contains 'a'");
        assertTrue(cycle.contains("b"), "Cycle contains 'b'");

    private final List<String> cycle;

    public CycleDetectedException(String message, List<String> cycle) {
        super(message);
        this.cycle = cycle;
    }

    public List<String> getCycle() {
        return cycle;
    }

    @Override
    public String getMessage() {
        return super.getMessage() + " " + String.join(" --> ", cycle);
    }

        private final List<String> cycle;

        CycleDetectedException(String message, List<String> cycle) {
            super(message);
            this.cycle = cycle;
        }

        public List<String> getCycle() {
            return cycle;
        }

        @Override
        public String getMessage() {
            return super.getMessage() + " " + String.join(" --> ", cycle);
        }
    }

        private final List<String> cycle;

        CycleDetectedException(String message, List<String> cycle) {
            super(message);
            this.cycle = cycle;
        }

        public List<String> getCycle() {
            return cycle;
        }

        @Override
        public String getMessage() {
            return super.getMessage() + " " + String.join(" --> ", cycle);
        }
    }