diff --git a/Cargo.lock b/Cargo.lock
index 68c8b34..6222abf 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -543,8 +543,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "wasm-pack"
 version = "0.1.0"
 dependencies = [
+ "failure 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "quicli 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.27 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_derive 1.0.27 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "toml 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index f5c6536..32cb53f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,7 +5,9 @@ version = "0.1.0"
 authors = ["Ashley Williams <ashley666ashley@gmail.com>"]
 
 [dependencies]
+failure = "0.1.1"
 quicli = "0.2"
 serde = "1.0"
+serde_derive = "1.0"
 serde_json = "1.0"
 toml = "0.4"
diff --git a/package.json b/package.json
deleted file mode 100644
index cb7ca0f..0000000
--- a/package.json
+++ /dev/null
@@ -1 +0,0 @@
-{"name":"wasm-pack","description":"pack up the wasm and publish it to npm!","version":"0.1.0"}
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..3696813
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,56 @@
+#[macro_use]
+extern crate serde_derive;
+extern crate serde_json;
+extern crate toml;
+extern crate failure;
+
+use std::fs::File;
+use std::io::prelude::*;
+
+use failure::Error;
+
+#[derive(Deserialize)]
+struct CargoManifest {
+    package: CargoPackage,
+}
+
+#[derive(Deserialize)]
+struct CargoPackage {
+    name: String,
+    description: String,
+    version: String,
+}
+
+#[derive(Serialize)]
+struct NpmPackage {
+    name: String,
+    description: String,
+    version: String,
+}
+
+fn read_cargo_toml() -> Result<CargoManifest, Error> {
+    let mut cargo_file = File::open("Cargo.toml")?;
+    let mut cargo_contents = String::new();
+    cargo_file.read_to_string(&mut cargo_contents)?;
+
+    Ok(toml::from_str(&cargo_contents)?)
+}
+
+impl CargoManifest {
+    fn into_npm(self) -> NpmPackage {
+        NpmPackage {
+            name: self.package.name,
+            description: self.package.description,
+            version: self.package.version,
+        }
+    }
+}
+
+pub fn write_package_json() -> Result<(), Error> {
+    let mut pkg_file = File::create("package.json")?;
+    let crate_data = read_cargo_toml()?;
+    let npm_data = crate_data.into_npm();
+    let npm_json = serde_json::to_string(&npm_data)?;
+    pkg_file.write_all(npm_json.as_bytes())?;
+    Ok(())
+}
diff --git a/src/main.rs b/src/main.rs
index d3494af..31c392a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,13 +1,9 @@
 #[macro_use]
 extern crate quicli;
-extern crate serde_json;
-extern crate toml;
+extern crate wasm_pack;
 
 use quicli::prelude::*;
 
-use std::fs::File;
-use std::io::prelude::*;
-
 /// 📦 ✨  pack and publish your wasm!
 #[derive(Debug, StructOpt)]
 struct Cli {
@@ -31,55 +27,9 @@ enum Command {
     Publish {},
 }
 
-#[derive(Deserialize)]
-pub struct CargoManifest {
-    package: CargoPackage,
-}
-
-#[derive(Deserialize)]
-pub struct CargoPackage {
-    name: String,
-    description: String,
-    version: String,
-}
-
-#[derive(Serialize)]
-pub struct NpmPackage {
-    name: String,
-    description: String,
-    version: String,
-}
-
-fn read_cargo_toml() -> Result<CargoManifest> {
-    let mut cargo_file = File::open("Cargo.toml")?;
-    let mut cargo_contents = String::new();
-    cargo_file.read_to_string(&mut cargo_contents)?;
-
-    Ok(toml::from_str(&cargo_contents)?)
-}
-
-impl CargoManifest {
-    fn into_npm(self) -> NpmPackage {
-        NpmPackage {
-            name: self.package.name,
-            description: self.package.description,
-            version: self.package.version,
-        }
-    }
-}
-
-fn write_package_json() -> Result<()> {
-    let mut pkg_file = File::create("package.json")?;
-    let crate_data = read_cargo_toml()?;
-    let npm_data = crate_data.into_npm();
-    let npm_json = serde_json::to_string(&npm_data)?;
-    pkg_file.write_all(npm_json.as_bytes())?;
-    Ok(())
-}
-
 main!(|args: Cli, log_level: verbosity| match args.cmd {
     Command::Init { .. } => {
-        write_package_json()?;
+        wasm_pack::write_package_json()?;
         println!("✍️  wrote a package.json!");
     }
     Command::Pack { .. } => {
diff --git a/tests/wasm-pack.rs b/tests/wasm-pack.rs
new file mode 100644
index 0000000..8093d18
--- /dev/null
+++ b/tests/wasm-pack.rs
@@ -0,0 +1,9 @@
+extern crate wasm_pack;
+
+use std::fs;
+
+#[test]
+fn it_creates_a_package_json() {
+    assert!(wasm_pack::write_package_json().is_ok());
+    assert!(fs::metadata("./package.json").is_ok());
+}