test code v1

tests/TC028-flat-plain-small.md

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+# Test Case: FLAT_PLAIN Small File
+
+**Test ID**: TC028-flat-plain-small
+
+## Objective
+
+Verify a sub-block regular file explicitly encoded as uncompressed
+`FLAT_PLAIN` reads source-exactly.
+
+## Fixture
+
+Use `images/flat.erofs` and `source/flat/small.txt`. Structured evidence asserts
+layout 0 and records NID and size.
+
+## Procedure
+
+```sh
+stat -f 'size=%z blocks=%b mode=%p' "$mnt/small.txt"
+cmp /tmp/repo22-g1/source/flat/small.txt "$mnt/small.txt"
+sha256 /tmp/repo22-g1/source/flat/small.txt "$mnt/small.txt"
+```
+
+## Expected Results
+
+- Evidence proves `FLAT_PLAIN`; size and data match the source.
+- The read, hash, mount, and cleanup all succeed.