Sometimes I want to test customized test cases for binary tree problems. Even with the help of the built-in tree visualizer, it’s pretty awkward to compose test cases for trees with height > 3. There are some 3rd party tree visualization tools. E.g.,
See-tree chrome extension allows to visualize a BT from selected strings from a web page. If you prefer a ascii-represented binary tree, check out the reop by gavinhub. The other github visualizer supports both tree and linked list.

Instead of drawing trees represented as strings, sites like btv.melezinek.cz and
datastructurex.com translates an interactively generatedly tree into serialized strings. https://datastructurex.com also generates Java, C++ and Python code for the generated tree, which would be convenient if you want to test the tree from your local ide. Note the tree searialization approach of btv.melezinek.cz differs from LC.