unikernel/duniverse/dune_/test/blackbox-tests/test-cases/digest-cache/README

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+This directory has various tests for the digest cache of Dune.
+
+In most of the tests, we use --wait-for-filesystem-clock to make the
+tests more reproducible. Without it, Dune might drop some entries or
+not depending on whether the time lap between targets being produced
+and dune saving the digest cache is smaller than the file system
+granularity.

unikernel/duniverse/dune_/test/blackbox-tests/test-cases/digest-cache/debug-option.t

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+Test the --debug-digests command line option
+
+  $ echo '(lang dune 3.0)' > dune-project
+  $ touch x
+  $ dune build x --wait-for-filesystem-clock
+  $ echo 1 > x
+  $ dune build x --wait-for-filesystem-clock --debug-digests 2>&1 | sed 's/stats =.*/stats = XXX/'
+  Re-digested file x because its stats changed:
+  { old_digest = digest "662cf3f7d59f76428301690d4ead67ae"
+  ; new_digest = digest "f31e1f1c33564e07cd02ad2c52f4df85"
+  ; old_stats = XXX
+  ; new_stats = XXX
+  }

unikernel/duniverse/dune_/test/blackbox-tests/test-cases/digest-cache/stats-used-in-db.t

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+Reproduction case for a bug we discovered in the past; Dune was
+storing the wrong stats for generated files in the digest cache and as
+a result was always re-hashing all files in the build directory on the
+second run.
+
+More precisely, we were using the stats of the file before making it
+read-only.
+
+
+  $ echo '(lang dune 3.0)' > dune-project
+  $ touch x y z
+  $ dune build x y z --wait-for-filesystem-clock
+
+Check that the next build rehashes nothing:
+
+  $ dune build x y z --wait-for-filesystem-clock --debug-digests 2>&1 | sed 's/stats = { .*\( perm = [0-9]*\).*}/stats = {\1; ... }/'