Complete coverage of tasks with visual tests

[shippy]

(copied over from #63)

Must-have visual tests:

• For each task, create enough tests to cover each outcome, probability, color, reference-side display.
• Stretch: Screencap each possible lottery and have a full run-through.
• Keyboard input / feedback display task: When the left-button is pressed, display left-button feedback, etc.
• Duration test: the entire test, from start to finish, lasts within delta of n seconds, no matter the press or non-press (for fMRI tasks)