keydr/docs/plans/2026-02-26-prevent-writing-to-user-data-in-tests.md

Prevent Tests from Writing to Real User Data

Context

Two tests in src/app.rs (adaptive_auto_continue_arms_input_lock and adaptive_does_not_auto_continue_with_milestones) call App::new() which connects to the real JsonStore at ~/.local/share/keydr/. When they call finish_drill() → save_data(), fake drill results get persisted to the user's actual history file. All other app tests also use App::new() but happen to not call finish_drill().

Changes

1. Add #[cfg(not(test))] gate on App::new() (src/app.rs:293)

Mark App::new() with #[cfg(not(test))] so it cannot be called from test code at all. This is a compile-time guarantee — any future test that tries App::new() will fail to compile.

2. Add App::new_test() (src/app.rs, in #[cfg(test)] block)

Add a pub fn new_test() constructor inside a #[cfg(test)] impl App block that mirrors App::new() but sets store: None. This prevents any persistence to disk. All existing fields get their default/empty values (no loading from disk either).

Since most test fields just need defaults and a started drill, the test constructor can be minimal:

• Config::default(), Theme::default() (leaked), Menu::new(), store: None
• Default key stats, skill tree, profile, empty drill history
• Dictionary::load(), TransitionTable, KeyboardModel — same as production (needed for start_drill())
• Call start_drill() at the end (same as App::new())

3. Update all existing tests to use App::new_test()

Replace every App::new() call in the test module with App::new_test(). This covers all 7 tests in #[cfg(test)] mod tests.

File to Modify

• src/app.rs — gate new(), add new_test(), update test calls

Verification

1. cargo test — all tests pass
2. cargo build — production build still compiles (ungated new() available)
3. Temporarily add App::new() in a test → should fail to compile