diff --git a/.circleci/config.yml b/.circleci/config.yml
new file mode 100644
index 0000000..8727aab
--- /dev/null
+++ b/.circleci/config.yml
@@ -0,0 +1,89 @@
+version: 2
+
+aliases:
+  # -------------------------
+  #      ALIASES: Caches
+  # -------------------------
+  - &restore-deps-cache
+    key: deps-cache-{{ checksum "package-lock.json" }}
+
+  - &save-deps-cache
+    key: deps-cache-{{ checksum "package-lock.json" }}
+    paths:
+      - ~/client-js/node_modules
+
+  # -------------------------
+  #  ALIASES: Branch Filters
+  # -------------------------
+  - &filter-only-master
+    branches:
+      only: master
+  - &filter-only-semantic-pr
+    branches:
+      only:  /^(pull|dependabot|fix|feat)\/.*$/
+
+defaults: &defaults
+  working_directory: ~/client-js
+
+jobs:
+  test:
+    <<: *defaults
+    docker:
+      - image: circleci/node:10
+    steps:
+      - checkout
+      - restore_cache: *restore-deps-cache
+      - run: npm install
+      - run: npm install codecov
+      - run: npm test
+      - run: ./node_modules/.bin/codecov
+      - save_cache: *save-deps-cache
+
+  build:
+    <<: *defaults
+    docker:
+      - image: circleci/node:10
+    steps:
+      - checkout
+      - restore_cache: *restore-deps-cache
+      - run: npm install
+      - run: npm run build
+      - save_cache: *save-deps-cache
+
+  release:
+    <<: *defaults
+    docker:
+      - image: circleci/node:10
+    steps:
+      - checkout
+      - restore_cache: *restore-deps-cache
+      - run: npm install
+      - run: npm run build
+      - run: npx semantic-release
+      - save_cache: *save-deps-cache
+
+workflows:
+  version: 2
+  analysis:
+    jobs:
+      - test:
+          filters: *filter-only-semantic-pr
+      - build:
+          filters: *filter-only-semantic-pr
+
+  release:
+    jobs:
+      - test:
+          filters: *filter-only-master
+      - build:
+          filters: *filter-only-master
+      - hold:
+          filters: *filter-only-master
+          type: approval
+          requires:
+            - test
+            - build
+      - release:
+          filters: *filter-only-master
+          requires:
+            - hold
diff --git a/src/RequestManager.test.ts b/src/RequestManager.test.ts
index a33eef2..d666f52 100644
--- a/src/RequestManager.test.ts
+++ b/src/RequestManager.test.ts
@@ -21,6 +21,12 @@ describe("client-js", () => {
     return c.connect();
   });
 
+  it("can close", () => {
+    const transport = new EventEmitterTransport("foo://unique-uri");
+    const c = new RequestManager([transport]);
+    c.close();
+  });
+
   it("can send a request", (done) => {
     const transport = new EventEmitterTransport("foo://unique-uri");
     const c = new RequestManager([transport]);
@@ -33,4 +39,12 @@ describe("client-js", () => {
     c.request("foo", []);
   });
 
+  it("can handle onData", () => {
+    const transport = new EventEmitterTransport("foo://unique-uri");
+    const c = new RequestManager([transport]);
+    const data = "{\"result\": \"bar\", \"id\": 1}";
+    c.request("foo", []);
+    c.onData(data);
+  });
+
 });
diff --git a/src/RequestManager.ts b/src/RequestManager.ts
index 7df1644..9f7c69e 100644
--- a/src/RequestManager.ts
+++ b/src/RequestManager.ts
@@ -33,8 +33,10 @@ class RequestManager {
       return;
     }
     // call request callback for id
-    this.requests[parsedData.id](parsedData);
-    delete this.requests[parsedData.id];
+    if (this.requests[parsedData.id]) {
+      this.requests[parsedData.id](parsedData);
+      delete this.requests[parsedData.id];
+    }
   }
   public async request(method: string, params: any): Promise<any> {
     await this.connectPromise;
diff --git a/src/__mocks__/isomorphic-fetch.ts b/src/__mocks__/isomorphic-fetch.ts
new file mode 100644
index 0000000..d24f65a
--- /dev/null
+++ b/src/__mocks__/isomorphic-fetch.ts
@@ -0,0 +1,10 @@
+const Fetch = (url: string, options: any): Promise<any> => {
+  const resultPromise = {
+    text: () => {
+      return Promise.resolve(options.body);
+    },
+  };
+  return Promise.resolve(resultPromise);
+};
+
+export default Fetch;
diff --git a/src/__mocks__/isomorphic-ws.ts b/src/__mocks__/isomorphic-ws.ts
new file mode 100644
index 0000000..a9763dc
--- /dev/null
+++ b/src/__mocks__/isomorphic-ws.ts
@@ -0,0 +1,28 @@
+class WebSocket {
+  private callbacks: any;
+  constructor(uri: string, props: any) {
+    this.callbacks = {};
+  }
+  public addEventListener(eventName: string, callback: any) {
+    this.callbacks[eventName] = callback;
+    if (eventName === "open") {
+      setTimeout(() => {
+        callback();
+      }, 10);
+    }
+  }
+  public removeEventListener(eventName: string, callback: any) {
+    delete this.callbacks[eventName];
+  }
+  public send(data: any) {
+    Object.entries(this.callbacks).forEach(([eventName, callback]: [string, any]) => {
+      if (eventName === "message") {
+        callback({data});
+      }
+    });
+  }
+  public close() {
+    this.callbacks = {};
+  }
+}
+export default WebSocket;
diff --git a/src/transports/HTTPTransport.test.ts b/src/transports/HTTPTransport.test.ts
new file mode 100644
index 0000000..7c57d4e
--- /dev/null
+++ b/src/transports/HTTPTransport.test.ts
@@ -0,0 +1,21 @@
+import HTTPTransport from "./HTTPTransport";
+
+describe("HTTPTransport", () => {
+  it("can connect", () => {
+    const wst = new HTTPTransport("http://localhost:8545");
+    return wst.connect();
+  });
+  it("can close", () => {
+    const wst = new HTTPTransport("http://localhost:8545");
+    wst.close();
+  });
+  it("can send and receive data", (done) => {
+    const wst = new HTTPTransport("http://localhost:8545");
+    wst.onData((data: any) => {
+      const d = JSON.parse(data);
+      expect(d.foo).toEqual("bar");
+      done();
+    });
+    wst.sendData(JSON.stringify({foo: "bar"}));
+  });
+});
diff --git a/src/transports/WebSocketTransport.test.ts b/src/transports/WebSocketTransport.test.ts
new file mode 100644
index 0000000..79845b8
--- /dev/null
+++ b/src/transports/WebSocketTransport.test.ts
@@ -0,0 +1,21 @@
+import WebSocketTransport from "./WebSocketTransport";
+
+describe("WebSocketTransport", () => {
+  it("can connect", () => {
+    const wst = new WebSocketTransport("http://localhost:8545");
+    return wst.connect();
+  });
+  it("can close", () => {
+    const wst = new WebSocketTransport("http://localhost:8545");
+    wst.close();
+  });
+  it("can send and receive data", (done) => {
+    const wst = new WebSocketTransport("http://localhost:8545");
+    wst.onData((data: any) => {
+      const d = JSON.parse(data);
+      expect(d.foo).toEqual("bar");
+      done();
+    });
+    wst.sendData(JSON.stringify({foo: "bar"}));
+  });
+});
diff --git a/src/transports/WebSocketTransport.ts b/src/transports/WebSocketTransport.ts
index 5215258..dbcdd47 100644
--- a/src/transports/WebSocketTransport.ts
+++ b/src/transports/WebSocketTransport.ts
@@ -1,10 +1,10 @@
-import WebSocket from "isomorphic-ws";
+import WS from "isomorphic-ws";
 import ITransport from "./Transport";
 
 class WebSocketTransport implements ITransport {
-  public connection: WebSocket;
+  public connection: WS;
   constructor(uri: string) {
-    this.connection = new WebSocket(uri);
+    this.connection = new WS(uri);
   }
   public connect(): Promise<any> {
     return new Promise((resolve, reject) => {