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tests/TC037-file-read-large.md

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+# Test Case: Large Regular-File Read
+
+**Test ID**: TC037-file-read-large
+
+## Objective
+
+Verify complete and distant-range reads of a deterministic file larger than
+100 MiB without a correctness shortcut based only on throughput.
+
+## Fixture
+
+Use `images/flat.erofs`, `source/flat/huge-data.bin`, and
+`expected/huge-sample.bin`. Evidence asserts layout 0 and size 104857857.
+
+## Procedure
+
+```sh
+stat -f 'size=%z blocks=%b' "$mnt/huge-data.bin"
+time dd if="$mnt/huge-data.bin" of=/tmp/tc037-full bs=1m
+cmp /tmp/repo22-g1/source/flat/huge-data.bin /tmp/tc037-full
+sha256 /tmp/repo22-g1/source/flat/huge-data.bin /tmp/tc037-full
+./read_probe pread "$mnt/huge-data.bin" 52428800 5242880 /tmp/tc037-sample
+cmp /tmp/repo22-g1/expected/huge-sample.bin /tmp/tc037-sample
+sha256 /tmp/repo22-g1/expected/huge-sample.bin /tmp/tc037-sample
+```
+
+Remove outputs, unmount, and detach.
+
+## Expected Results
+
+- Exact size, full compare, and 50 MiB-offset sample compare all pass.
+- Record elapsed time but impose no host-dependent QEMU throughput threshold.
+- No memory exhaustion, panic, or cleanup failure occurs.