- you need to create a test case for each if statement and you need to provide each time a suitable feed from your service, so I suggest that you use spies instead of referencing you real FlagService
- create a global fixture so you don’t have to instantiate it for every test case
- You do not need to call .detectChanges since you already call ngOnInit.
Please see the below project, that cover 100% your appComponent. (https://github.com/IsmailDiari/stackoverflow-anglar-jasmine-code-coverage).
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