Improve test coverage across frontend-component-header

[PKulkoRaccoonGang]

Description

Currently, a significant number of components in the frontend-component-header repository lack sufficient test coverage. This makes the codebase harder to maintain, increases the risk of regressions, and slows down development when introducing new features or refactoring existing code.

Below is the latest coverage report:

File	% Stmts	% Branch	% Funcs	% Lines	Uncovered Line #s
All files	75.88	43.78	61.85	76.29
src	88.57	76.92	75	88.57
Avatar.jsx	100	50	100	100	12
Header.jsx	93.75	79.16	50	93.75	29
Header.messages.jsx	100	100	100	100
Icons.jsx	100	100	100	100
Logo.jsx	100	100	100	100
frontend-platform.d.ts	0	0	0	0
index.jsx	0	0	0	0
test-utils.js	0	100	0	0	1-3
src/Menu	33.98	7.14	39.13	33.66
Menu.jsx	33.98	7.14	39.13	33.66	64-164,179-216
index.jsx	0	0	0	0
src/desktop-header	87.8	39.28	76.92	88.88
DesktopHeader.jsx	100	75	100	100	60
DesktopHeaderMainOrSecondaryMenu.jsx	80	50	100	80	10,37
DesktopHeaderUserMenu.jsx	50	0	0	60	6-11
DesktopLoggedOutItems.jsx	100	100	100	100
DesktopUserMenuToggle.jsx	100	100	100	100
src/generic	100	100	100	100
messages.js	100	100	100	100
src/i18n	0	0	0	0
index.js	0	0	0	0
src/learning-header	81.57	60	50	86.11
AnonymousUserMenu.jsx	25	100	0	25	11-24
AuthenticatedUserDropdown.jsx	100	50	100	100	29
LearningHeader.jsx	100	83.33	100	100	48
LearningHeaderCourseInfo.jsx	100	100	100	100
LearningHeaderHelpLink.jsx	100	100	100	100
LearningHeaderUserMenuItems.jsx	60	100	0	75	7
LearningLoggedOutButtons.jsx	60	0	0	75	7
LearningUserMenuToggle.jsx	100	100	100	100
messages.js	100	100	100	100
src/mobile-header	71.42	25	46.15	71.42
MobileHeader.jsx	100	66.66	100	100	47-81
MobileHeaderMainMenu.jsx	30	0	0	30	8-36
MobileHeaderUserMenu.jsx	50	0	0	60	5-8
MobileLoggedOutItems.jsx	60	0	0	75	5
MobileUserMenuToggle.jsx	100	100	100	100
src/plugin-slots/CourseInfoSlot	100	100	100	100
index.jsx	100	100	100	100
src/plugin-slots/DesktopHeaderSlot	100	100	100	100
index.jsx	100	100	100	100
src/plugin-slots/DesktopLoggedOutItemsSlot	100	100	100	100
index.jsx	100	100	100	100
src/plugin-slots/DesktopMainMenuSlot	100	100	100	100
index.jsx	100	100	100	100
src/plugin-slots/DesktopSecondaryMenuSlot	100	100	100	100
index.jsx	100	100	100	100
src/plugin-slots/DesktopUserMenuSlot	66.66	100	0	66.66
index.jsx	66.66	100	0	66.66	8
src/plugin-slots/DesktopUserMenuToggleSlot	100	100	100	100
index.jsx	100	100	100	100
src/plugin-slots/LearningHelpSlot	100	100	100	100
index.jsx	100	100	100	100
src/plugin-slots/LearningLoggedOutItemsSlot	66.66	100	0	66.66
index.jsx	66.66	100	0	66.66	8
src/plugin-slots/LearningUserMenuSlot	66.66	100	0	66.66
index.jsx	66.66	100	0	66.66	8
src/plugin-slots/LearningUserMenuToggleSlot	100	100	100	100
index.jsx	100	100	100	100
src/plugin-slots/LogoSlot	100	100	100	100
index.jsx	100	100	100	100
src/plugin-slots/MobileHeaderSlot	100	100	100	100
index.jsx	100	100	100	100
src/plugin-slots/MobileLoggedOutItemsSlot	66.66	100	0	66.66
index.jsx	66.66	100	0	66.66	8
src/plugin-slots/MobileMainMenuSlot	66.66	100	0	66.66
index.jsx	66.66	100	0	66.66	8
src/plugin-slots/MobileUserMenuSlot	66.66	100	0	66.66
index.jsx	66.66	100	0	66.66	8
src/plugin-slots/MobileUserMenuToggleSlot	100	100	100	100
index.jsx	100	100	100	100
src/studio-header	100	83.87	100	100
BrandNav.tsx	100	100	100	100
CourseLockUp.tsx	100	100	100	100
HeaderBody.tsx	100	91.66	100	100	55
MobileHeader.tsx	100	100	100	100
MobileMenu.tsx	100	100	100	100
NavDropdownMenu.tsx	100	100	100	100
StudioHeader.tsx	100	71.42	100	100	31-34
UserMenu.tsx	100	100	100	100
index.ts	100	100	100	100
messages.ts	100	100	100	100
utils.ts	100	100	100	100

[PKulkoRaccoonGang]

@arbrandes @brian-smith-tcril considering that in the future MFEs will use the header provided by frontend-base, does it still make sense to add tests for this frontend-component-header repository?

[PKulkoRaccoonGang]

Comment from @arbrandes

It might take a little while for us to fully migrate to frontend-base, but frontend-component-header's days are numbered. I would not spend too much time on it.