diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index fb637bf..3ba139e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -63,6 +63,8 @@ jobs:
           key: guest-bundle-${{ steps.guest-keys.outputs.guest-key }}
       - name: Install clang
         run: sudo apt-get update && sudo apt-get install -y clang
+      - name: Test JavaScript guest build
+        run: just wasm js-guest-test
       - name: Build guests
         run: just wasm guest-bundle
       - name: Upload guest bundle
diff --git a/Justfile b/Justfile
index 9e3280a..6d87c5a 100644
--- a/Justfile
+++ b/Justfile
@@ -32,7 +32,7 @@ fmt-check-rust:
 
 #### TESTS ####
 
-test: wasm::test-build wasm::guest-build wasm::js-guest-build python::build python::python-test test-rust wasm::test dotnet::test-rust dotnet::test
+test: wasm::test-build wasm::js-guest-test wasm::guest-build wasm::js-guest-build python::build python::python-test test-rust wasm::test dotnet::test-rust dotnet::test
 
 fuzz seconds="60": (python::python-fuzz seconds)
 
diff --git a/src/wasm_sandbox/Justfile b/src/wasm_sandbox/Justfile
index 789dc77..fbe4891 100644
--- a/src/wasm_sandbox/Justfile
+++ b/src/wasm_sandbox/Justfile
@@ -101,6 +101,11 @@ js-guest-build: js-guest-build-wasm js-guest-build-aot
 js-guest-install:
     uv run --no-project --python 3.14 python {{repo-root}}/scripts/guest_build.py javascript
 
+# Test componentization against the installed JavaScript dependencies.
+js-guest-test:
+    cd {{repo-root}}/src/wasm_sandbox/guests/javascript && npm ci
+    cd {{repo-root}}/src/wasm_sandbox/guests/javascript && npm test
+
 build target=default-target: _clean-stale-wasm (guest-build target) (js-guest-build)
     cargo build --manifest-path {{repo-root}}/src/wasm_sandbox/Cargo.toml --profile={{ if target == "debug" {"dev"} else { target } }}
 
diff --git a/src/wasm_sandbox/guests/javascript/build.js b/src/wasm_sandbox/guests/javascript/build.js
index 2293510..79ead71 100644
--- a/src/wasm_sandbox/guests/javascript/build.js
+++ b/src/wasm_sandbox/guests/javascript/build.js
@@ -32,10 +32,11 @@ const outputPath = "js-sandbox.wasm";
 async function build() {
   console.log("Reading source...");
   const source = await readFile(sourcePath, "utf-8");
+  const witWorld = await readFile(witPath, "utf-8");
 
   console.log("Componentizing...");
   const { component, imports } = await componentize(source, {
-    witPath,
+    witWorld,
     worldName: "hyperlight:sandbox/sandbox",
   });
 
diff --git a/src/wasm_sandbox/guests/javascript/build.test.js b/src/wasm_sandbox/guests/javascript/build.test.js
new file mode 100644
index 0000000..d70cf33
--- /dev/null
+++ b/src/wasm_sandbox/guests/javascript/build.test.js
@@ -0,0 +1,15 @@
+import assert from "node:assert/strict";
+import { execFile } from "node:child_process";
+import { readFile } from "node:fs/promises";
+import { promisify } from "node:util";
+import { test } from "node:test";
+
+test("builds the JavaScript component with the installed WASI shim", async () => {
+  const cwd = new URL(".", import.meta.url);
+  await promisify(execFile)(process.execPath, ["build.js"], {
+    cwd,
+    timeout: 120_000,
+  });
+  const component = await readFile(new URL("js-sandbox.wasm", cwd));
+  assert.deepEqual(component.subarray(0, 8), Buffer.from([0, 97, 115, 109, 13, 0, 1, 0]));
+});
diff --git a/src/wasm_sandbox/guests/javascript/package-lock.json b/src/wasm_sandbox/guests/javascript/package-lock.json
index cad2781..8b68542 100644
--- a/src/wasm_sandbox/guests/javascript/package-lock.json
+++ b/src/wasm_sandbox/guests/javascript/package-lock.json
@@ -10,7 +10,7 @@
       "devDependencies": {
         "@bytecodealliance/componentize-js": "^0.23.0",
         "@bytecodealliance/jco": "^1.39.0",
-        "@bytecodealliance/preview2-shim": "^0.25.0"
+        "@bytecodealliance/preview2-shim": "^0.31.0"
       }
     },
     "node_modules/@andreiltd/componentize-qjs-binding-darwin-arm64": {
@@ -453,9 +453,9 @@
       }
     },
     "node_modules/@bytecodealliance/preview2-shim": {
-      "version": "0.25.0",
-      "resolved": "https://registry.npmjs.org/@bytecodealliance/preview2-shim/-/preview2-shim-0.25.0.tgz",
-      "integrity": "sha512-6ZSDRJ8hJc/febZepzd68z3KzLcOXyCOKtRm8LB2rgAU88xV7ykq6dMb5I4a+sBh1cuV2Yb1159gDzI1q8UsoQ==",
+      "version": "0.31.0",
+      "resolved": "https://registry.npmjs.org/@bytecodealliance/preview2-shim/-/preview2-shim-0.31.0.tgz",
+      "integrity": "sha512-9Gv4wn/DCz1NOqTZFcPSIko9jsTwmps67QZ6PPytypmmWLSz5AQf3Xn2EjItfudWwSh5d+9EPD3BrNlvqKWNtA==",
       "dev": true,
       "license": "(Apache-2.0 WITH LLVM-exception)",
       "dependencies": {
diff --git a/src/wasm_sandbox/guests/javascript/package.json b/src/wasm_sandbox/guests/javascript/package.json
index cbb922e..d71e641 100644
--- a/src/wasm_sandbox/guests/javascript/package.json
+++ b/src/wasm_sandbox/guests/javascript/package.json
@@ -4,11 +4,12 @@
   "private": true,
   "type": "module",
   "scripts": {
-    "build": "node build.js"
+    "build": "node build.js",
+    "test": "node --test build.test.js"
   },
   "devDependencies": {
     "@bytecodealliance/componentize-js": "^0.23.0",
     "@bytecodealliance/jco": "^1.39.0",
-    "@bytecodealliance/preview2-shim": "^0.25.0"
+    "@bytecodealliance/preview2-shim": "^0.31.0"
   }
 }