diff --git a/assembly/src/assembler/mast_forest_merger_tests.rs b/assembly/src/assembler/mast_forest_merger_tests.rs
new file mode 100644
index 000000000..9d1b9faba
--- /dev/null
+++ b/assembly/src/assembler/mast_forest_merger_tests.rs
@@ -0,0 +1,67 @@
+use std::vec::Vec;
+
+use miette::{IntoDiagnostic, Report};
+use vm_core::mast::{MastForest, MastForestRootMap};
+
+use crate::{testing::TestContext, Assembler};
+
+#[allow(clippy::type_complexity)]
+fn merge_programs(
+    program_a: &str,
+    program_b: &str,
+) -> Result<(MastForest, MastForest, (MastForest, Vec<MastForestRootMap>)), Report> {
+    let context = TestContext::new();
+    let module = context.parse_module_with_path("lib::mod".parse().unwrap(), program_a)?;
+
+    let lib_a = Assembler::new(context.source_manager()).assemble_library([module])?;
+
+    let mut assembler = Assembler::new(context.source_manager());
+    assembler.add_library(lib_a.clone())?;
+    let lib_b = assembler.assemble_library([program_b])?.mast_forest().as_ref().clone();
+    let lib_a = lib_a.mast_forest().as_ref().clone();
+
+    let merged = MastForest::merge([&lib_a, &lib_b]).into_diagnostic()?;
+
+    Ok((lib_a, lib_b, merged))
+}
+
+/// Tests that an assembler-produced library's forests can be merged and that external nodes are
+/// replaced by their referenced procedures.
+#[test]
+fn mast_forest_merge_assembler() {
+    let lib_a = r#"
+  export.foo
+      push.19
+  end
+"#;
+
+    let lib_b = r#"
+  use.lib::mod
+
+  export.bar
+      push.2
+      if.true
+          push.3
+      else
+          while.true
+              add
+              push.23
+          end
+      end
+      exec.mod::foo
+  end"#;
+
+    let (forest_a, forest_b, (merged, root_maps)) = merge_programs(lib_a, lib_b).unwrap();
+
+    for (forest, root_map) in [(forest_a, &root_maps[0]), (forest_b, &root_maps[1])] {
+        for root in forest.procedure_roots() {
+            let original_digest = forest.nodes()[root.as_usize()].digest();
+            let new_root = root_map.map_root(root).unwrap();
+            let new_digest = forest.nodes()[new_root.as_usize()].digest();
+            assert_eq!(original_digest, new_digest);
+        }
+    }
+
+    // Assert that the external node for the import was removed during merging.
+    merged.nodes().iter().for_each(|node| assert!(!node.is_external()));
+}
diff --git a/assembly/src/assembler/mod.rs b/assembly/src/assembler/mod.rs
index 6575056e9..2ddc94e31 100644
--- a/assembly/src/assembler/mod.rs
+++ b/assembly/src/assembler/mod.rs
@@ -28,6 +28,9 @@ mod procedure;
 #[cfg(test)]
 mod tests;
 
+#[cfg(test)]
+mod mast_forest_merger_tests;
+
 use self::{
     basic_block_builder::BasicBlockBuilder,
     module_graph::{CallerInfo, ModuleGraph, ResolvedTarget},