diff --git a/test/unit/fix-request-body.spec.ts b/test/unit/fix-request-body.spec.ts
new file mode 100644
index 00000000..6ea56ba0
--- /dev/null
+++ b/test/unit/fix-request-body.spec.ts
@@ -0,0 +1,66 @@
+import { ClientRequest } from 'http';
+import * as querystring from 'querystring';
+
+import { fixRequestBody } from '../../src/handlers/fix-request-body';
+import type { Request } from '../../src/types';
+
+const fakeProxyRequest = () => {
+  const proxyRequest = new ClientRequest('http://some-host');
+  proxyRequest.emit = jest.fn();
+
+  return proxyRequest;
+};
+
+describe('fixRequestBody', () => {
+  it('should not write when body is undefined', () => {
+    const proxyRequest = fakeProxyRequest();
+
+    jest.spyOn(proxyRequest, 'setHeader');
+    jest.spyOn(proxyRequest, 'write');
+
+    fixRequestBody(proxyRequest, { body: undefined } as Request);
+
+    expect(proxyRequest.setHeader).not.toHaveBeenCalled();
+    expect(proxyRequest.write).not.toHaveBeenCalled();
+  });
+
+  it('should not write when body is empty', () => {
+    const proxyRequest = fakeProxyRequest();
+
+    jest.spyOn(proxyRequest, 'setHeader');
+    jest.spyOn(proxyRequest, 'write');
+
+    fixRequestBody(proxyRequest, { body: {} } as Request);
+
+    expect(proxyRequest.setHeader).not.toHaveBeenCalled();
+    expect(proxyRequest.write).not.toHaveBeenCalled();
+  });
+
+  it('should write when body is not empty and Content-Type is application/json', () => {
+    const proxyRequest = fakeProxyRequest();
+    proxyRequest.setHeader('content-type', 'application/json; charset=utf-8');
+
+    jest.spyOn(proxyRequest, 'setHeader');
+    jest.spyOn(proxyRequest, 'write');
+
+    fixRequestBody(proxyRequest, { body: { someField: 'some value' } } as Request);
+
+    const expectedBody = JSON.stringify({ someField: 'some value' });
+    expect(proxyRequest.setHeader).toHaveBeenCalledWith('Content-Length', expectedBody.length);
+    expect(proxyRequest.write).toHaveBeenCalledWith(expectedBody);
+  });
+
+  it('should write when body is not empty and Content-Type is application/x-www-form-urlencoded', () => {
+    const proxyRequest = fakeProxyRequest();
+    proxyRequest.setHeader('content-type', 'application/x-www-form-urlencoded');
+
+    jest.spyOn(proxyRequest, 'setHeader');
+    jest.spyOn(proxyRequest, 'write');
+
+    fixRequestBody(proxyRequest, { body: { someField: 'some value' } } as Request);
+
+    const expectedBody = querystring.stringify({ someField: 'some value' });
+    expect(proxyRequest.setHeader).toHaveBeenCalledWith('Content-Length', expectedBody.length);
+    expect(proxyRequest.write).toHaveBeenCalledWith(expectedBody);
+  });
+});
diff --git a/test/unit/response-interceptor.spec.ts b/test/unit/response-interceptor.spec.ts
new file mode 100644
index 00000000..09bfc548
--- /dev/null
+++ b/test/unit/response-interceptor.spec.ts
@@ -0,0 +1,63 @@
+import { IncomingMessage, ServerResponse } from 'http';
+
+import { responseInterceptor } from '../../src/handlers/response-interceptor';
+
+const fakeProxyResponse = () => {
+  const httpIncomingMessage = new IncomingMessage(null);
+  httpIncomingMessage._read = () => ({});
+  return httpIncomingMessage;
+};
+
+const fakeResponse = () => {
+  const httpIncomingMessage = fakeProxyResponse();
+
+  const response = new ServerResponse(httpIncomingMessage);
+  response.setHeader = jest.fn();
+  response.write = jest.fn();
+  response.end = jest.fn();
+
+  return response;
+};
+
+const waitInterceptorHandler = (ms = 1): Promise<void> =>
+  new Promise((resolve) => setTimeout(resolve, ms));
+
+describe('responseInterceptor', () => {
+  it('should write body on end proxy event', async () => {
+    const httpIncomingMessage = fakeProxyResponse();
+    const response = fakeResponse();
+
+    responseInterceptor(async () => JSON.stringify({ someField: '' }))(
+      httpIncomingMessage,
+      null,
+      response
+    );
+
+    httpIncomingMessage.emit('end');
+    await waitInterceptorHandler();
+
+    const expectedBody = JSON.stringify({ someField: '' });
+    expect(response.setHeader).toHaveBeenCalledWith('content-length', expectedBody.length);
+    expect(response.write).toHaveBeenCalledWith(Buffer.from(expectedBody));
+    expect(response.end).toHaveBeenCalledWith();
+  });
+
+  it('should end with error when receive a proxy error event', async () => {
+    const httpIncomingMessage = fakeProxyResponse();
+    const response = fakeResponse();
+
+    responseInterceptor(async () => JSON.stringify({ someField: '' }))(
+      httpIncomingMessage,
+      null,
+      response
+    );
+
+    httpIncomingMessage.emit('error', new Error('some error meessage'));
+
+    expect(response.setHeader).not.toHaveBeenCalled();
+    expect(response.write).not.toHaveBeenCalled();
+    expect(response.end).toHaveBeenCalledWith(
+      'Error fetching proxied request: some error meessage'
+    );
+  });
+});