Add test cases

[BonfaceKilz]

Description

Right now, we are manually running through the following manual test cases to ensure things are working properly(the list may change overtime)

1. npm start runs and loads code into the browser window automatically.
2. Browser window should show the expected test pattern.
3. Browser refresh reloads the view.
4. Browser window should show Input widgets at top: filename, start bin, left and right buttons, path name, position, jump button, Use Vertical Compression, Row Height, Column Width.
5. Browser window starts populated with a graphic showing the current data.
6. Light grey blocks for coverage (shouldn't be everywhere). Dark grey connectors in between Components (light grey background boxes).
7. Links appear as colorful arrows immediately above the Component boxes.
8. Link Color matches Box Color in the Column immediately below either end of the link.
9. Links horizontal runs stack up neatly without overlapping (broken in current screenshot).
10. Mouse over Link and it changes to black.
11. Click Orphan Link (only one small arrow). View should jump to corresponding section with the other side of the link and matching color.
12. Matching link is visually highlighted (#6 not implemented yet).
13. Clicking on the newly highlighted link should take you back to precisely where you came from (2-way link travel) with your orphan link centered in the view.
14. Mouseover cells (grey blocks) should show e.g. "Path_name: 2365-27289. Coverage: 0.23, Inversion: 0.0". Mouseovers should be different for each cell. Mouseover disappears when not over cell.

We can always automate that and check that using some end-to-end testing framework like cypress and let the linter do all the important tests for us in CI when someone submits a PR, that way the reviewer's work is reduced to reviewing other aspects of the code like checking logic errors, or improving code structure.

[BonfaceKilz]

@josiahseaman you can assign this to me to research and add basic end-to-end testing(if possible) for this project. IMHO it will make our work easier. Wdyt?