public void DFS1() { var dfs = new DFS <int>(); var tree = BuildBunchOfIntNodes(); Assert.False(dfs.Contains(tree, 1)); Assert.False(dfs.Contains(null, 1)); Assert.True(dfs.Contains(tree, 10)); Assert.True(dfs.Contains(tree, 45)); Assert.True(dfs.Contains(tree, 25)); Assert.False(dfs.Contains(tree, 125)); }