diff --git a/test/blackbox-tests/cross-module-optimizations.t b/test/blackbox-tests/cross-module-optimizations.t
new file mode 100644
index 000000000..4d2e43ee2
--- /dev/null
+++ b/test/blackbox-tests/cross-module-optimizations.t
@@ -0,0 +1,204 @@
+Showcase cross-module optimizations
+
+  $ . ./setup.sh
+  $ cat > dune-project <<EOF
+  > (lang dune 3.13)
+  > (using melange 0.1)
+  > EOF
+
+Same module
+
+  $ cat > dune <<EOF
+  > (melange.emit
+  >  (target output)
+  >  (emit_stdlib false))
+  > EOF
+
+  $ cat > x.ml <<EOF
+  > let compose f g x = f (g x)
+  > let logPlusTwo = compose Js.log ((+) 2)
+  > EOF
+
+  $ dune build @melange
+  $ cat _build/default/output/x.js
+  // Generated by Melange
+  'use strict';
+  
+  const Curry = require("melange.js/curry.js");
+  
+  function compose(f, g, x) {
+    return Curry._1(f, Curry._1(g, x));
+  }
+  
+  function logPlusTwo(param) {
+    console.log(2 + param | 0);
+  }
+  
+  exports.compose = compose;
+  exports.logPlusTwo = logPlusTwo;
+  /* No side effect */
+
+Different modules
+
+  $ cat > util.ml <<EOF
+  > let compose f g x = f (g x)
+  > EOF
+
+  $ cat > x.ml <<EOF
+  > let logPlusTwo = Util.compose Js.log ((+) 2)
+  > EOF
+  $ dune clean
+  $ dune build @melange
+  $ cat _build/default/output/x.js
+  // Generated by Melange
+  'use strict';
+  
+  const Melange__Util = require("./util.js");
+  
+  function logPlusTwo(param) {
+    return Melange__Util.compose((function (prim) {
+            console.log(prim);
+          }), (function (param) {
+            return 2 + param | 0;
+          }), param);
+  }
+  
+  exports.logPlusTwo = logPlusTwo;
+  /* No side effect */
+
+Different modules with cross-module-optimizations
+
+  $ cat > dune <<EOF
+  > (melange.emit
+  >  (target output)
+  >  (emit_stdlib false)
+  >  (compile_flags :standard --mel-cross-module-opt))
+  > EOF
+
+  $ dune clean
+  $ dune build @melange
+  $ cat _build/default/output/x.js
+  // Generated by Melange
+  'use strict';
+  
+  const Curry = require("melange.js/curry.js");
+  
+  function logPlusTwo(param) {
+    console.log(Curry._1((function (param) {
+                return 2 + param | 0;
+              }), param));
+  }
+  
+  exports.logPlusTwo = logPlusTwo;
+  /* No side effect */
+
+Library dependency
+
+  $ cat > dune <<EOF
+  > (library
+  >  (name lib)
+  >  (modes melange)
+  >  (modules util))
+  > 
+  > (melange.emit
+  >  (target output)
+  >  (emit_stdlib false)
+  >  (libraries lib)
+  >  (modules x))
+  > EOF
+
+  $ cat > x.ml <<EOF
+  > let logPlusTwo = Lib.Util.compose Js.log ((+) 2)
+  > EOF
+
+  $ dune clean
+  $ dune build @melange
+  $ cat _build/default/output/x.js
+  // Generated by Melange
+  'use strict';
+  
+  const Lib__Util = require("./util.js");
+  
+  function logPlusTwo(param) {
+    return Lib__Util.compose((function (prim) {
+            console.log(prim);
+          }), (function (param) {
+            return 2 + param | 0;
+          }), param);
+  }
+  
+  exports.logPlusTwo = logPlusTwo;
+  /* No side effect */
+
+Library dependency with cross-module optimizations
+
+  $ cat > dune <<EOF
+  > (library
+  >  (name lib)
+  >  (modes melange)
+  >  (modules util))
+  > 
+  > (melange.emit
+  >  (target output)
+  >  (emit_stdlib false)
+  >  (libraries lib)
+  >  (modules x)
+  >  (compile_flags :standard --mel-cross-module-opt))
+  > EOF
+
+  $ cat > x.ml <<EOF
+  > let logPlusTwo = Lib.Util.compose Js.log ((+) 2)
+  > EOF
+
+  $ dune clean
+  $ dune build @melange
+  $ cat _build/default/output/x.js
+  // Generated by Melange
+  'use strict';
+  
+  const Lib__Util = require("./util.js");
+  
+  function logPlusTwo(param) {
+    return Lib__Util.compose((function (prim) {
+            console.log(prim);
+          }), (function (param) {
+            return 2 + param | 0;
+          }), param);
+  }
+  
+  exports.logPlusTwo = logPlusTwo;
+  /* No side effect */
+
+Only works across library-boundaries if the library dependency is also compiled
+with `--mel-cross-module-opt`
+
+  $ cat > dune <<EOF
+  > (library
+  >  (name lib)
+  >  (modes melange)
+  >  (modules util)
+  >  (melange.compile_flags :standard --mel-cross-module-opt))
+  > 
+  > (melange.emit
+  >  (target output)
+  >  (emit_stdlib false)
+  >  (libraries lib)
+  >  (modules x)
+  >  (compile_flags :standard --mel-cross-module-opt))
+  > EOF
+  $ dune clean
+  $ dune build @melange
+  $ cat _build/default/output/x.js
+  // Generated by Melange
+  'use strict';
+  
+  const Curry = require("melange.js/curry.js");
+  
+  function logPlusTwo(param) {
+    console.log(Curry._1((function (param) {
+                return 2 + param | 0;
+              }), param));
+  }
+  
+  exports.logPlusTwo = logPlusTwo;
+  /* No side effect */