diff --git a/assembly/hello-world/index.ts b/assembly/hello-world/index.ts
index b63dcde..1888808 100644
--- a/assembly/hello-world/index.ts
+++ b/assembly/hello-world/index.ts
@@ -1,5 +1,14 @@
 import * as env from '../env'
 
+/**
+ * Examples for linking a library
+ */
+@external("add", "incr")
+export declare function incr(a: u32): u32
+
+@external("add", "add")
+export declare function add(a: u32, b: u32): u32
+
 /*
  * Increments preStateRoot by one
  */
@@ -10,7 +19,8 @@ export function main(): void {
   var postStateRootPtr: u32 = __heap_base + 32
 
   var numPtr: u32 = __heap_base + 64
-  store<u8>(numPtr, 1, 31)
+  // Silly example of how you can use lib
+  store<u8>(numPtr, add(0, 1), 31)
 
   env.bignum_add256(preStateRootPtr, numPtr, postStateRootPtr)
 
diff --git a/assembly/lib/add.ts b/assembly/lib/add.ts
new file mode 100644
index 0000000..c5530ca
--- /dev/null
+++ b/assembly/lib/add.ts
@@ -0,0 +1,7 @@
+export function incr(a: u32): u32 {
+  return a + 1
+}
+
+export function add(a: u32, b: u32): u32 {
+  return a + b
+}
diff --git a/package.json b/package.json
index b6755b9..d18444d 100644
--- a/package.json
+++ b/package.json
@@ -30,7 +30,8 @@
     "docs": "typedoc --out docs --mode modules --theme markdown --excludeNotExported src",
     "asbuild:untouched": "asc assembly/hello-world/index.ts -b build/hello-world-untouched.wasm -t build/hello-world-untouched.wat --sourceMap --validate --debug",
     "asbuild:optimized": "asc assembly/hello-world/index.ts -b build/hello-world-optimized.wasm -t build/hello-world-optimized.wat --sourceMap --validate --optimize",
-    "asbuild": "npm run asbuild:untouched && npm run asbuild:optimized"
+    "asbuild": "npm run asbuild:untouched && npm run asbuild:optimized",
+    "asbuild:lib": "asc assembly/lib/add.ts -b build/lib-add-optimized.wasm -t build/lib-add-optimized.wat --sourceMap --validate --optimize"
   },
   "author": "s1na",
   "license": "Apache-2.0",
diff --git a/src/cli.ts b/src/cli.ts
index 742cda7..6be08c3 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -22,7 +22,10 @@ function main() {
     const wasmModule = new WebAssembly.Module(wasmFile)
     let preStateRoot = testCase.preStateRoot
     for (const block of testCase.blocks) {
-      const instance = new WebAssembly.Instance(wasmModule, getImports({ preStateRoot, blockData: block }))
+      let libExports = getLibExports(testCase.libs)
+      let imports = getImports({ preStateRoot, blockData: block })
+      imports = { ...imports, ...libExports }
+      const instance = new WebAssembly.Instance(wasmModule, imports)
       setMemory(instance.exports.memory)
       let t = process.hrtime()
       instance.exports.main()
@@ -34,4 +37,27 @@ function main() {
   }
 }
 
+interface Exports {
+  // { libName: { exportName: Fn } }
+  [n: string]: { [f: string]: Function }
+}
+
+function getLibExports(libs: { [k: string]: string }): Exports {
+  let libExports: Exports = {}
+  for (const libName in libs) {
+    const libFile = fs.readFileSync(libs[libName])
+    const libModule = new WebAssembly.Module(libFile)
+    const libInstance = new WebAssembly.Instance(libModule, { env: { abort: () => { throw new Error('Wasm aborted') } } })
+    const exports: { [k: string]: Function } = {}
+    for (const fn in libInstance.exports) {
+      if (fn === 'memory' || fn.startsWith('_')) {
+        continue
+      }
+      exports[fn] = libInstance.exports[fn]
+    }
+    libExports[libName] = exports
+  }
+  return libExports
+}
+
 main()
diff --git a/src/lib.ts b/src/lib.ts
index 20c2597..2aa9c7a 100644
--- a/src/lib.ts
+++ b/src/lib.ts
@@ -29,6 +29,7 @@ export interface ShardBlock {
 
 export interface TestCase {
   script: string
+  libs: { [k: string]: string } // { name: file }
   preStateRoot: Buffer
   blocks: Buffer[]
   postStateRoot: Buffer
@@ -100,6 +101,9 @@ export const getImports = (env: EnvData) => {
 export function parseYaml (file: string): TestCase[] {
   const testCase = safeLoad(file)
   const scripts = testCase.beacon_state.execution_scripts
+  const libs = (testCase.beacon_state.libraries || []).reduce(
+    (a: { [k: string]: string }, v: { name: string, file: string }) => { a[v.name] = v.file; return a }, {}
+  )
   const shardBlocks = testCase.shard_blocks
   const testCases = []
   for (let i = 0; i < scripts.length; i++) {
@@ -118,6 +122,7 @@ export function parseYaml (file: string): TestCase[] {
 
     testCases.push({
       script,
+      libs,
       preStateRoot,
       postStateRoot,
       blocks
diff --git a/test.yaml b/test.yaml
index a491ad2..40e52fc 100644
--- a/test.yaml
+++ b/test.yaml
@@ -1,6 +1,9 @@
 beacon_state:
   execution_scripts:
     - build/hello-world-optimized.wasm
+  libraries:
+    - name: "add"
+      file: build/lib-add-optimized.wasm
 shard_pre_state:
   exec_env_states:
     - "0000000000000000000000000000000000000000000000000000000000000001"