Step to Reproduce:
When running the below segment of code as junit test, the code didn't cover for the listTrails and findTrailsByDifficulty functions.
	private ClimbingMode cm = ClimbingMode.getInstance();
	@Test
	public void testTrailListing() {
		ClimbingTrailRepoManager ctrm = new ClimbingTrailRepoManagerStub();
		String actualString = ctrm.list();
		String expectedString = "Test trail";
		assertEquals(expectedString, actualString);

	}

	@Test
	public void testFilterDifficulty() {
		ClimbingTrailRepoManager ctrm = new ClimbingTrailRepoManagerStub();
		String actualString = ctrm.filterByDifficulty(8);
		String expectedString = "Test trail";
		assertEquals(expectedString, actualString);

	}

Actual Result: 
The listTrails and findTrailsByDifficulty functions are not covered.


Expected Result: 
The test code coverage should increase, the code in the ClimbingMode class, listTrails and findTrailsByDifficulty, should be covered.