crud tests for subjects, assignments and tasks

notes/work-report-2026-04-24-to-25.md

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+# CRUD Testing Summary (React Native + Jest + Supabase)
+
+## What these tests are about
+Tests verify **app behavior**, not Supabase itself.
+
+They check:
+- User interaction works
+- Correct database functions are called
+- Navigation happens after actions
+
+---
+
+## CRUD Breakdown
+
+### CREATE
+- User inputs data
+- `insert()` is called
+- App navigates back
+
+Flow:
+User → type → press create → insert() → router.back()
+
+---
+
+### READ
+- Data is fetched (`select().eq().single()`)
+- State updates
+- UI renders correct content
+
+---
+
+### UPDATE
+- Existing data is loaded
+- User edits input
+- `update().eq()` is called with correct values
+- Navigation happens
+
+---
+
+### DELETE
+- User presses delete
+- `Alert.alert()` is triggered
+- Confirm button (`onPress`) is manually called in test
+- `delete().eq()` runs
+- Navigation happens
+
+---
+
+## Why mocking is used
+- No real database calls
+- Faster tests
+- Full control over success/error cases
+- No side effects (no real data created/deleted)
+
+---
+
+## Mock rule
+The mock must match the real call chain:
+
+Real:
+from → update → eq → select → single
+
+Mock:
+from() → update() → eq() → select() → single()
+
+If not → errors like:
+".select is not a function"
+
+---
+
+https://oss.callstack.com/react-native-testing-library/