ocaml · Leonidas-from-XIV · Dec 23, 2025 · Dec 22, 2025
diff --git a/test/blackbox-tests/test-cases/pkg/build-package-logs.t b/test/blackbox-tests/test-cases/pkg/build-package-logs.t
@@ -20,7 +20,7 @@ Create a package with a failing command that throws an error:
 
 Building the package should fail and print an error:
 
-  $ build_pkg x 2>&1 | sed -E 's#/.*/cat#cat#g'
+  $ build_pkg x 2>&1 | dune_cmd subst '/.*/cat' cat
   File "dune.lock/x.pkg", line 4, characters 11-14:
   4 |       (run cat i_dont_exist)))
                  ^^^

diff --git a/test/blackbox-tests/test-cases/pkg/commit-hash-references.t b/test/blackbox-tests/test-cases/pkg/commit-hash-references.t
@@ -30,5 +30,5 @@ Depend on foo from the repo
 
 Which foo will we get?
 
-  $ dune pkg lock 2>&1 | grep "not found" | sed "s/$AMBIGUOUS_REF/\$AMBIGUOUS_REF/g"
+  $ dune pkg lock 2>&1 | grep "not found" | dune_cmd subst "$AMBIGUOUS_REF" '$AMBIGUOUS_REF'
   revision "$AMBIGUOUS_REF" not found in
diff --git a/test/blackbox-tests/test-cases/pkg/conflicts.t b/test/blackbox-tests/test-cases/pkg/conflicts.t
@@ -69,7 +69,7 @@ Even though the conflicts are listed by opam without a `|` to indicate a
 disjunction, either package is problematic:
 
   $ mkpkg dune 3.11
-  $ echo '(lang dune 3.11)' | solve_project 2>&1 | sed -E 's/3.[0-9]+/3.XX/'
+  $ echo '(lang dune 3.11)' | solve_project 2>&1 | dune_cmd subst '3.[0-9]+' '3.XX'
   Error:
   Unable to solve dependencies while generating lock directory: dune.lock
 
@@ -87,7 +87,7 @@ disjunction, either package is problematic:
 Adding a new version of `foo` only resolves one conflict:
 
   $ mkpkg foo 0.2
-  $ echo '(lang dune 3.11)' | solve_project 2>&1 | sed -E 's/3.[0-9]+/3.XX/'
+  $ echo '(lang dune 3.11)' | solve_project 2>&1 | dune_cmd subst '3.[0-9]+' '3.XX'
   Error:
   Unable to solve dependencies while generating lock directory: dune.lock
 

diff --git a/test/blackbox-tests/test-cases/pkg/extra-sources.t b/test/blackbox-tests/test-cases/pkg/extra-sources.t
@@ -111,7 +111,7 @@ url and the extra source.
   Solution for dune.lock:
   - needs-patch.0.0.1
 
-  $ sed -E 's/md5=[0-9a-f]+/md5=$HASH/g' ${default_lock_dir}/needs-patch.0.0.1.pkg
+  $ dune_cmd subst 'md5=[0-9a-f]+' 'md5=$HASH'< "${default_lock_dir}/needs-patch.0.0.1.pkg"
   (version 0.0.1)
 
   (build

diff --git a/test/blackbox-tests/test-cases/pkg/implicit-dune-constraint.t b/test/blackbox-tests/test-cases/pkg/implicit-dune-constraint.t
@@ -12,7 +12,7 @@ dependency.
   > solve foo
   > }
 
-  $ test "2.0.0" 2>&1 | sed -E 's/3.[0-9]+/3.XX/g'
+  $ test "2.0.0" 2>&1 | dune_cmd subst '3.[0-9]+' '3.XX'
   Error:
   Unable to solve dependencies while generating lock directory: dune.lock
 
@@ -27,7 +27,7 @@ dependency.
   Solution for dune.lock:
   - foo.0.0.1
 
-  $ test "4.0.0" 2>&1 | sed -E 's/3.[0-9]+/3.XX/g'
+  $ test "4.0.0" 2>&1 | dune_cmd subst '3.[0-9]+' '3.XX'
   Solution for dune.lock:
   - foo.0.0.1
 

diff --git a/test/blackbox-tests/test-cases/pkg/install-missing-entry.t b/test/blackbox-tests/test-cases/pkg/install-missing-entry.t
@@ -12,7 +12,7 @@ Test missing entries in the .install file
 This should give us a proper error that myfile wasn't generated
 
   $ lockfile "myfile"
-  $ build_pkg test 2>&1 | sed 's#_build.*_private#$ROOT/_private#'
+  $ build_pkg test 2>&1 | dune_cmd subst '_build.*_private' '$ROOT/_private'
   Error: entry
   $ROOT/_private/default/.pkg/test.0.0.1-962f24dc2cb394442fe86368a850a9d0/source/myfile
   in

diff --git a/test/blackbox-tests/test-cases/pkg/invalid-opam-repo-errors.t/run.t b/test/blackbox-tests/test-cases/pkg/invalid-opam-repo-errors.t/run.t
@@ -10,8 +10,9 @@ Test the error cases for invalid opam repositories
   $ lock() {
   > out="$(dune pkg lock 2>&1)"
   > local code="$?"
-  > echo "$out" | sed 's/character.*:/characters X-X:/g' \
-  >   | sed 's/url ".*"/url ../g' \
+  > echo "$out" \
+  >   | dune_cmd subst 'character.*:' 'characters X-X:' \
+  >   | dune_cmd subst 'url ".*"' 'url ..' \
   >   | grep -v "\^"
   > return $code
   > }

diff --git a/test/blackbox-tests/test-cases/pkg/log-solution.t b/test/blackbox-tests/test-cases/pkg/log-solution.t
@@ -36,7 +36,7 @@ It should also work when the lock dir is generated by Dune:
 
 We should be seeing that it has created a lock dir solution depending on foo.0.0.2:
 
-  $ sed -n -e "/Dependency solution for/,\$p" _build/log | grep '^#' | sed 's#.sandbox/[a-f0-9]*#.sandbox/$HASH#'
+  $ sed -n -e '/Dependency solution for/,$p' _build/log | grep '^#' | dune_cmd subst '.sandbox/[a-f0-9]*' '.sandbox/$HASH'
   # Dependency solution for
   # _build/.sandbox/$HASH/_private/default/.lock/dune.lock:
   # - foo.0.0.2

diff --git a/test/blackbox-tests/test-cases/pkg/ocamlformat/ocamlformat-custom-build-dir.t b/test/blackbox-tests/test-cases/pkg/ocamlformat/ocamlformat-custom-build-dir.t
@@ -16,7 +16,7 @@ the build directory in `$dev_tool_lock_dir` with our custom build directory.
   $ default_build_dir="_build"
   $ custom_build_dir="_other_build"
   $ default_dev_tool_lock_dir="${dev_tool_lock_dir}"
-  $ dev_tool_lock_dir=$(echo "${dev_tool_lock_dir}" | sed "s/^$default_build_dir/$custom_build_dir/")
+  $ dev_tool_lock_dir=$(echo "${dev_tool_lock_dir}" | dune_cmd subst "^$default_build_dir" "$custom_build_dir")
 
 Create a configuration with this custom build directory
 

diff --git a/test/blackbox-tests/test-cases/pkg/opam-package-with-files-install.t b/test/blackbox-tests/test-cases/pkg/opam-package-with-files-install.t
@@ -8,4 +8,4 @@ file copying step rather than the build step.
   $ echo "(version 0.0.1)" > ${default_lock_dir}/foo.pkg
 
 The foo.install file in files/ should have been copied over.
-  $ build_pkg foo 2>&1 | sed 's/copyfile/open/'
+  $ build_pkg foo
diff --git a/test/blackbox-tests/test-cases/pkg/opam-source-conversion.t b/test/blackbox-tests/test-cases/pkg/opam-source-conversion.t
@@ -36,11 +36,11 @@ Test conversion of opam sources into lock dir package specifications
 
   $ rm -rf ${default_lock_dir}
 
-  $ solve testpkg 2>&1 | sed -E 's#.*.sandbox/[^/]+#.sandbox/$SANDBOX#g' | sed '/File "/q'
+  $ solve testpkg
   Solution for dune.lock:
   - testpkg.0.0.1
 
-  $ showpkg | sed -e "s#$PWD#<pwd>#"
+  $ showpkg | dune_cmd subst "$PWD" '<pwd>'
   (version 0.0.1)
 
   (source

diff --git a/test/blackbox-tests/test-cases/pkg/opam-var/opam-var-global.t b/test/blackbox-tests/test-cases/pkg/opam-var/opam-var-global.t
@@ -43,6 +43,6 @@ Therefore we modify the lockfile here to remove these from the opam file:
 The value for "jobs" should always be 1.
 
   $ GROUP="$(id -gn)"
-  > build_pkg testpkg 2>&1 | sed "s/$GROUP/GROUP/g"
+  > build_pkg testpkg 2>&1 | dune_cmd subst "$GROUP" 'GROUP'
   1
   GROUP
diff --git a/test/blackbox-tests/test-cases/pkg/opam-var/opam-var-os.t b/test/blackbox-tests/test-cases/pkg/opam-var/opam-var-os.t
@@ -74,5 +74,5 @@ separately here:
   - testpkg.0.0.1
 
   $ ocaml_version="$(ocaml -vnum)"
-  $ build_pkg testpkg 2>&1 | sed "s/$ocaml_version/OCAML_VERSION/g"
+  $ build_pkg testpkg 2>&1 | dune_cmd subst "$ocaml_version" 'OCAML_VERSION'
   OCAML_VERSION
diff --git a/test/blackbox-tests/test-cases/pkg/opam-var/opam-var-switch.t b/test/blackbox-tests/test-cases/pkg/opam-var/opam-var-switch.t
@@ -47,7 +47,7 @@ opam-var-unsupported.t
        (run echo %{toplevel})
        (run echo %{stublibs}))))))
 
-  $ build_pkg testpkg 2>&1 | sed -E 's#.*.sandbox/[^/]+#.sandbox/$SANDBOX#g'
+  $ build_pkg testpkg 2>&1 | dune_cmd subst '.*.sandbox/[^/]+' '.sandbox/$SANDBOX'
   dune
   .sandbox/$SANDBOX/_private/default/.pkg/testpkg.0.0.1-d349dc24837a78e7f391d386e4fcec8d/source
   .sandbox/$SANDBOX/_private/default/.pkg/testpkg.0.0.1-d349dc24837a78e7f391d386e4fcec8d/target

diff --git a/test/blackbox-tests/test-cases/pkg/pin-depends.t b/test/blackbox-tests/test-cases/pkg/pin-depends.t
@@ -194,7 +194,7 @@ Pin to an HTTP archive detects wrong hash
   >  (name foo)
   >  (libraries bar))
   > EOF
-  $ sed -i.tmp "s/$MD5_CHECKSUM/92449184682b45b5f07e811fdd61d35f/g" ${default_lock_dir}/bar.1.0.0.pkg
+  $ dune_cmd subst "$MD5_CHECKSUM" '92449184682b45b5f07e811fdd61d35f' ${default_lock_dir}/bar.1.0.0.pkg
   $ rm -rf already-served
   $ dune build 2>&1 | grep -v "md5"
   File "dune.lock/bar.1.0.0.pkg", line 6, characters 12-48:

diff --git a/test/blackbox-tests/test-cases/pkg/pin-stanza/git-source-nested.t b/test/blackbox-tests/test-cases/pkg/pin-stanza/git-source-nested.t
@@ -27,7 +27,7 @@ Package sources can be set to git and be nested:
   >  (package (name bar)))
   > EOF
 
-  $ dune pkg lock 2>&1 | sed 's#git+file://.*/#$URL#'
+  $ dune pkg lock 2>&1 | dune_cmd subst 'git\+file://.*/' '$URL'
   File "dune-project", line 5, characters 1-21:
   5 |  (package (name bar)))
        ^^^^^^^^^^^^^^^^^^^^

diff --git a/test/blackbox-tests/test-cases/pkg/pin-stanza/git-source.t b/test/blackbox-tests/test-cases/pkg/pin-stanza/git-source.t
@@ -67,7 +67,7 @@ than the tag is pointing to (still the initial commit):
 
 In this case Dune can't determine which reference to use and will error out:
 
-  $ dune_pkg_lock_normalized 2>&1 | sed "s|$PWD|\$PWD|"
+  $ dune_pkg_lock_normalized 2>&1 | dune_cmd subst "$PWD" '$PWD'
   Error: Reference "duplicated" in remote
   "file://$PWD/_repo"
   is ambiguous

diff --git a/test/blackbox-tests/test-cases/pkg/pin-stanza/no-package.t b/test/blackbox-tests/test-cases/pkg/pin-stanza/no-package.t
@@ -19,7 +19,7 @@ Here we try to pin a package to a source that doesn't define said package:
   >  (depends bar))
   > EOF
 
-  $ dune pkg lock 2>&1 | sed 's#file://.*#$URL#g'
+  $ dune pkg lock 2>&1 | dune_cmd subst 'file://.*' '$URL'
   File "dune-project", line 4, characters 1-21:
   4 |  (package (name bar)))
        ^^^^^^^^^^^^^^^^^^^^

diff --git a/test/blackbox-tests/test-cases/pkg/pin-stanza/unknown-dune-version.t b/test/blackbox-tests/test-cases/pkg/pin-stanza/unknown-dune-version.t
@@ -22,7 +22,7 @@ We are unable to pin projects that the version of dune doesn't understand.
 # The location here is messed up b/c we are using a source path (incorrectly)
 # to construct the project
 
-  $ dune pkg lock 2>&1 | sed -E 's/3.[0-9]+/3.XX/g'
+  $ dune pkg lock 2>&1 | dune_cmd subst '3.[0-9]+' '3.XX'
   File "dune-project", line 1, characters 11-16:
   1 | (lang dune 3.XX)
                  ^^^^^

diff --git a/test/blackbox-tests/test-cases/pkg/pkg-extract-fail.t b/test/blackbox-tests/test-cases/pkg/pkg-extract-fail.t
@@ -16,7 +16,7 @@ build this package and check for sufficient error handling
   $ solve foo
   Solution for dune.lock:
   - foo.0.0.1
-  $ build_pkg foo 2>&1 |  sed -ne '/Error:/,$ p' | sed '/^Reason/ q' | sed "s/'[0-9]*'/X/"
+  $ build_pkg foo 2>&1 |  sed -ne '/Error:/,$ p' | sed '/^Reason/ q' | dune_cmd subst "'[0-9]*'" X
   Error: failed to extract 'corrupted.tar'
   Reason: 'tar' failed with non-zero exit code X and output:
 
@@ -35,7 +35,7 @@ captured
   Solution for dune.lock:
   - foo.0.0.1
 
-  $ build_pkg foo 2>&1 |  sed -ne '/Error:/,$ p' | sed '/^Reason/ q' | sed "s/'[0-9]*'/X/"
+  $ build_pkg foo 2>&1 |  sed -ne '/Error:/,$ p' | sed '/^Reason/ q' | dune_cmd subst "'[0-9]*'" X
   Error: failed to extract 'corrupted.tar.gz'
   Reason: 'tar' failed with non-zero exit code X and output:
 
@@ -56,6 +56,6 @@ unzip error message a bit less clear
   Solution for dune.lock:
   - foo.0.0.1
 
-  $ build_pkg foo 2>&1 | sed -ne '/Error:/,$ p' | sed '/^Reason/ q' | sed "s/'[0-9]*'/X/"
+  $ build_pkg foo 2>&1 | sed -ne '/Error:/,$ p' | sed '/^Reason/ q' | dune_cmd subst "'[0-9]*'" X
   Error: failed to extract 'corrupted.zip'
   Reason: 'unzip' failed with non-zero exit code X and output:
diff --git a/test/blackbox-tests/test-cases/pkg/set-ocamlfind-destdir.t b/test/blackbox-tests/test-cases/pkg/set-ocamlfind-destdir.t
@@ -8,6 +8,8 @@ install and build commands.
   > (install (run sh -c "echo [install] OCAMLFIND_DESTDIR=$OCAMLFIND_DESTDIR"))
   > EOF
 
-  $ build_pkg test 2>&1 | sed "s#$(pwd)#PWD#" | sed 's#\.sandbox/.*/_private#\.sandbox/SANDBOX/_private#'
+  $ build_pkg test 2>&1 \
+  > | dune_cmd subst "$PWD" PWD \
+  > | dune_cmd subst '\.sandbox/.*/_private' '.sandbox/SANDBOX/_private'
   [build] OCAMLFIND_DESTDIR=PWD/_build/.sandbox/SANDBOX/_private/default/.pkg/test.0.0.1-b793a9f8326ede0e03bacae4740bd81b/target/lib
   [install] OCAMLFIND_DESTDIR=PWD/_build/.sandbox/SANDBOX/_private/default/.pkg/test.0.0.1-b793a9f8326ede0e03bacae4740bd81b/target/lib
diff --git a/test/blackbox-tests/test-cases/pkg/substitute.t b/test/blackbox-tests/test-cases/pkg/substitute.t
@@ -87,7 +87,7 @@ Now with variables set
   >   (substitute defined.ml.in defined.ml)
   >   (system "cat defined.ml")))
   > EOF
-  $ build_pkg test 2>&1 | sed 's/%{os}% is.*/%{os}% is $REDACTED/g'
+  $ build_pkg test 2>&1 | dune_cmd subst '%\{os\}% is.*' '%{os}% is $REDACTED'
   We substitute '%{name}%' into 'test' and '%{_:name}%' into 'test'
   And '%{version}%' is set to '0.0.1'
   There is also some paths set:

diff --git a/test/blackbox-tests/test-cases/pkg/toolchain-installation.t b/test/blackbox-tests/test-cases/pkg/toolchain-installation.t
@@ -72,13 +72,13 @@ variable which includes the test sandbox path which is different each
 time the tests runs. Strip the hash out of the toolchain directory
 name so the output is consistent across test runs.
   $ remove_hash() {
-  >   sed 's/\(ocaml-base-compiler.1-\)[^/]*/\1HASH/'
+  >   dune_cmd subst 'ocaml-base-compiler.1-[^/]+' 'ocaml-base-compiler.1-HASH'
   > }
 
 Attempt to build the project. This will fail due to the fake compiler,
 but the fake compiler will end up installed as a toolchain package.
 Also test that XDG_CACHE_HOME is respected.
-  $ XDG_CACHE_HOME=$PWD/fake-cache DUNE_CONFIG__TOOLCHAINS=enabled build_pkg ocaml-base-compiler 2>&1 | remove_hash
+  $ XDG_CACHE_HOME=$PWD/fake-cache DUNE_CONFIG__TOOLCHAINS=enabled build_pkg ocaml-base-compiler
 
 Enumerate the contents of the fake toolchains directory:
   $ find fake-cache/dune/toolchains | sort | remove_hash
@@ -89,7 +89,7 @@ Enumerate the contents of the fake toolchains directory:
   fake-cache/dune/toolchains/ocaml-base-compiler.1-HASH/target/bin/ocamlc
 
 Also test that DUNE_CACHE_ROOT is respected.
-  $ DUNE_CACHE_ROOT=$PWD/other-fake-cache DUNE_CONFIG__TOOLCHAINS=enabled build_pkg ocaml-base-compiler 2>&1 | remove_hash
+  $ DUNE_CACHE_ROOT=$PWD/other-fake-cache DUNE_CONFIG__TOOLCHAINS=enabled build_pkg ocaml-base-compiler
 
 Enumerate the contents of the fake toolchains directory:
   $ find other-fake-cache/toolchains/ | sort | remove_hash

diff --git a/test/blackbox-tests/test-cases/pkg/toolchain-variables.t b/test/blackbox-tests/test-cases/pkg/toolchain-variables.t
@@ -82,6 +82,8 @@ We generate a fake package to use it
 We try to build the dependency to show that it echoes the wong path. Until we
 fix the problem, it shows the sandbox path
 
-  $ XDG_CACHE_HOME=$PWD/fake-cache dune build @pkg-install 2>&1 | sed -E 's#[[:alnum:]]{32}#<hash>#g' | sed 's#[^ ]*_build#$TESTCASE_ROOT/_build#g'
+  $ XDG_CACHE_HOME=$PWD/fake-cache dune build @pkg-install 2>&1 \
+  > | dune_cmd subst '[[:alnum:]]{32}' '<hash>' \
+  > | dune_cmd subst '[^ ]*_build' '$TESTCASE_ROOT/_build'
   $TESTCASE_ROOT/_build/.sandbox/<hash>/_private/default/.pkg/ocaml-base-compiler.1-<hash>/target/share/ocaml-base-compiler
 
diff --git a/test/blackbox-tests/test-cases/pkg/unavailable-package-source.t b/test/blackbox-tests/test-cases/pkg/unavailable-package-source.t
@@ -12,17 +12,20 @@ Demonstrate what happens when we try to fetch from a source that doesn't exist:
   > }
 
 Local file system
-  $ runtest "(copy \"$PWD/dummy\")" 2>&1 | sed "s#$(pwd)#PWD#" | sed '/ *^\^*$/d' | sed '\#^File ".*dune.lock/foo.pkg", line 2, characters#d'
+  $ runtest "(copy \"$PWD/dummy\")" 2>&1 \
+  >  | dune_cmd subst "$PWD" 'PWD' \
+  >  | dune_cmd delete ' *\^\^*$' \
+  >  | dune_cmd delete '^File ".*dune.lock/foo.pkg", line 2, characters'
   2 | (source (copy "PWD/dummy"))
   Error:
   PWD/dummy
   does not exist
 
 Git
   $ runtest "(fetch (url \"git+file://$PWD/dummy\"))" 2>&1 \
-  > | sed "s#$(pwd)#PWD#" \
+  > | dune_cmd subst "$PWD" 'PWD' \
   > | sanitize_pkg_digest foo.dev \
-  > | sed -E 's#/url/[a-f0-9]+#/url/DIGEST#'
+  > | dune_cmd subst '/url/[a-f0-9]+' '/url/DIGEST'
   fatal: 'PWD/dummy' does not appear to be a git repository
   fatal: Could not read from remote repository.
 
@@ -40,6 +43,9 @@ Git
 
 HTTP
 
-  $ runtest "(fetch (url \"https://0.0.0.0:35000\"))" 2>&1 | sed -ne '/Error:/,$ p' | sed '/^Reason/ q' | sed "s/'[0-9]*'/X/"
+  $ runtest "(fetch (url \"https://0.0.0.0:35000\"))" 2>&1 \
+  >  | sed -ne '/Error:/,$ p' \
+  >  | sed '/^Reason/ q' \
+  >  | dune_cmd subst "'[0-9]*'" 'X'
   Error: failed to extract 'download'
   Reason: 'tar' failed with non-zero exit code X and output:
diff --git a/test/blackbox-tests/test-cases/pkg/variables.t b/test/blackbox-tests/test-cases/pkg/variables.t
@@ -58,7 +58,7 @@ Now we demonstrate we get a proper error from invalid .config files:
   >  ))
   > EOF
 
-  $ build_pkg test 2>&1 | sed 's/File .*:/File $REDACTED:/'
+  $ build_pkg test 2>&1 | dune_cmd subst 'File .*:' 'File $REDACTED:'
   Error:
   File $REDACTED:
   1 | this is dummy text

diff --git a/test/blackbox-tests/test-cases/pkg/withenv-path.t b/test/blackbox-tests/test-cases/pkg/withenv-path.t
@@ -4,6 +4,11 @@ using the withenv action.
 This path is system-specific so we need to be able to remove it from the output.
   $ DUNE_PATH=$(dirname $(which dune))
 
+To workaround some shell weirdness about setting variables like PATH in the
+presence of shell functions we use dune_cmd with an absolute path:
+
+  $ DUNE_CMD=$(which dune_cmd)
+
   $ make_lockdir
 
 Make some packages so that the test package can have dependencies:
@@ -21,7 +26,7 @@ Printing out PATH without setting it:
   >  (system "echo PATH=$PATH"))
   > EOF
   $ dune clean
-  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | sed -e "s#$DUNE_PATH#DUNE_PATH#"
+  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | $DUNE_CMD subst "$DUNE_PATH" 'DUNE_PATH'
   PATH=DUNE_PATH:/bin
 
 Setting PATH to a specific value:
@@ -33,7 +38,7 @@ Setting PATH to a specific value:
   >   (system "echo PATH=$PATH")))
   > EOF
   $ dune clean
-  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | sed -e "s#$DUNE_PATH#DUNE_PATH#"
+  $ PATH=$DUNE_PATH:/bin build_pkg test
   PATH=/tmp/bin
 
 Attempting to add a path to PATH replaces the entire PATH:
@@ -45,7 +50,7 @@ Attempting to add a path to PATH replaces the entire PATH:
   >   (system "echo PATH=$PATH")))
   > EOF
   $ dune clean
-  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | sed -e "s#$DUNE_PATH#DUNE_PATH#"
+  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | $DUNE_CMD subst "$DUNE_PATH" 'DUNE_PATH'
   PATH=/tmp/bin:DUNE_PATH:/bin
 
 Try adding multiple paths to PATH:
@@ -59,7 +64,7 @@ Try adding multiple paths to PATH:
   >   (system "echo PATH=$PATH")))
   > EOF
   $ dune clean
-  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | sed -e "s#$DUNE_PATH#DUNE_PATH#"
+  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | $DUNE_CMD subst "$DUNE_PATH" 'DUNE_PATH'
   PATH=/bar/bin:/foo/bin:/tmp/bin:DUNE_PATH:/bin
 
 Printing out PATH without setting it when the package has a dependency:
@@ -70,7 +75,7 @@ Printing out PATH without setting it when the package has a dependency:
   >  (system "echo PATH=$PATH"))
   > EOF
   $ dune clean
-  $ OCAMLRUNPARAM=b PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | sed -e "s#$DUNE_PATH#DUNE_PATH#"
+  $ OCAMLRUNPARAM=b PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | $DUNE_CMD subst "$DUNE_PATH" 'DUNE_PATH'
   PATH=$TESTCASE_ROOT/_build/_private/default/.pkg/hello2.0.0.1-3cf268d89ba7f04a10a17a1a00d6d508/target/bin:$TESTCASE_ROOT/_build/_private/default/.pkg/hello1.0.0.1-2bbe9250d988b3a1dc98ca2cf6f9ab0c/target/bin:DUNE_PATH:/bin
 
 Setting PATH to a specific value:
@@ -83,7 +88,7 @@ Setting PATH to a specific value:
   >   (system "echo PATH=$PATH")))
   > EOF
   $ dune clean
-  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | sed -e "s#$DUNE_PATH#DUNE_PATH#"
+  $ PATH=$DUNE_PATH:/bin build_pkg test
   PATH=/tmp/bin
 
 Attempting to add a path to PATH replaces the entire PATH:
@@ -96,7 +101,7 @@ Attempting to add a path to PATH replaces the entire PATH:
   >   (system "echo PATH=$PATH")))
   > EOF
   $ dune clean
-  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | sed -e "s#$DUNE_PATH#DUNE_PATH#"
+  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | $DUNE_CMD subst "$DUNE_PATH" 'DUNE_PATH'
   PATH=/tmp/bin:$TESTCASE_ROOT/_build/_private/default/.pkg/hello2.0.0.1-3cf268d89ba7f04a10a17a1a00d6d508/target/bin:$TESTCASE_ROOT/_build/_private/default/.pkg/hello1.0.0.1-2bbe9250d988b3a1dc98ca2cf6f9ab0c/target/bin:DUNE_PATH:/bin
 
 Try adding multiple paths to PATH:
@@ -111,5 +116,5 @@ Try adding multiple paths to PATH:
   >   (system "echo PATH=$PATH")))
   > EOF
   $ dune clean
-  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | sed -e "s#$DUNE_PATH#DUNE_PATH#"
+  $ PATH=$DUNE_PATH:/bin build_pkg test 2>&1 | $DUNE_CMD subst "$DUNE_PATH" 'DUNE_PATH'
   PATH=/bar/bin:/foo/bin:/tmp/bin:$TESTCASE_ROOT/_build/_private/default/.pkg/hello2.0.0.1-3cf268d89ba7f04a10a17a1a00d6d508/target/bin:$TESTCASE_ROOT/_build/_private/default/.pkg/hello1.0.0.1-2bbe9250d988b3a1dc98ca2cf6f9ab0c/target/bin:DUNE_PATH:/bin