Increase coverage and consistency of trip planner tests #5717

Job	Run time
Build application and assets	1m 3s
Build Docker image	1m 3s
file_changes	6s
Linting / JavaScript	31s
Linting / Elixir	48s
Unit tests / JavaScript / Mocha	34s
Linting / CSS	32s
Linting / TypeScript	40s
Type checks / Elixir	36s
Type checks / TypeScript	35s
Formatting / Elixir	46s
Formatting / JavaScript & TypeScript	30s
Unit tests / JavaScript & TypeScript / Jest	47s
Unit tests / Elixir / mix coveralls.html	1s
	8m 32s

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