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tests/TC080-prefix-table-lookup.md

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+# Test Case: Prefix table lookup
+
+**Test ID**: TC080-prefix-table-lookup
+**Fixture**: `basic.erofs`, `/prefix-user-0` through `/prefix-user-3`
+
+## Objective
+
+Verify repeated prefix-ID lookup and a clean missing-suffix result.
+
+## Manual steps
+
+Run the following lookup separately for suffix files 0, 1, 2, and 3:
+
+```sh
+getextattr -qq -x user repo22.application.component.setting \
+  /mnt/repo22-g4/prefix-user-N
+truss -o /tmp/tc080.truss getextattr -qq user \
+  repo22.application.component.missing /mnt/repo22-g4/prefix-user-0
+grep extattr_get_file /tmp/tc080.truss
+```
+
+## Expected results
+
+Values are `prefix-value-N` for each file; the missing suffix is `ENOATTR`
+(87), not an integrity failure. Unmount and detach.