diff --git a/__tests__/Events.spec.js b/__tests__/Events.spec.js
index 85fb61f..465cc49 100644
--- a/__tests__/Events.spec.js
+++ b/__tests__/Events.spec.js
@@ -1,3 +1,4 @@
+const { buildParams } = require('./helpers')
 const Events = require('../lib/Events')
 const Logger = require('../lib/Logger')
 
@@ -34,8 +35,11 @@ describe('Events class', function () {
         },
       ],
     ])('valid options value', function (options) {
+      const urlParams = buildParams(options)
       API.listEvents(options)
+
       expect(Request.get).toHaveBeenCalledTimes(1)
+      expect(Request.get).toHaveBeenCalledWith(`/events?${urlParams}`)
     })
 
     test.each([
@@ -44,50 +48,58 @@ describe('Events class', function () {
       [{ query: {} }],
       [{ subcalendarId: 'id' }],
       [{ format: 'text' }],
+      [{ startDate: '' }],
+      [{ endDate: undefined }],
+      [{ subcalendarId: undefined }],
     ])('invalid options value', function (options) {
       expect(() => API.listEvents(options)).toThrow()
     })
 
-    test.each([
-      [{}],
-      [{ startDate: '' }],
-      [{ endDate: undefined }],
-      [{ query: false }],
-      [{ subcalendarId: null }],
-      [{ format: 0 }],
-    ])('ignored options value', function (options) {
-      API.listEvents(options)
-      expect(Request.get).toHaveBeenCalledTimes(1)
-    })
+    test.each([[{}], [{ subcalendarId: null }]])(
+      'ignored options value',
+      function (options) {
+        API.listEvents(options)
+        expect(Request.get).toHaveBeenCalledTimes(1)
+        expect(Request.get).toHaveBeenCalledWith(`/events`)
+      }
+    )
 
     test('invalid option parameter', function () {
       expect(() => API.listEvents({ someKey: true })).toThrow()
     })
 
-    test.each([[], 'string', true, false, 123])(
+    test.each([[], 'string', true, false, 123, null])(
       'invalid options',
       function (option) {
         expect(() => API.listEvents(option)).toThrow()
       }
     )
+
+    test('ignored option: undefined', function () {
+      API.listEvents(undefined)
+      expect(Request.get).toHaveBeenCalledTimes(1)
+      expect(Request.get).toHaveBeenCalledWith(`/events`)
+    })
   })
 
   describe('method: listEvent', function () {
     test('with event id (number)', function () {
       API.listEvent(1234)
       expect(Request.get).toHaveBeenCalledTimes(1)
+      expect(Request.get).toHaveBeenCalledWith(`/events/1234`)
     })
 
     test('with event id (string)', function () {
       API.listEvent('1234')
       expect(Request.get).toHaveBeenCalledTimes(1)
+      expect(Request.get).toHaveBeenCalledWith(`/events/1234`)
     })
 
     test('without event id', function () {
       expect(() => API.listEvent()).toThrow()
     })
 
-    test.each([[], 'string', true, false, {}])(
+    test.each([[], 'string', true, false, {}, null, undefined])(
       'invalid event id',
       function (id) {
         expect(() => API.listEvent(id)).toThrow()
diff --git a/__tests__/SubCalendar.spec.js b/__tests__/SubCalendar.spec.js
index 45663e4..88f52d6 100644
--- a/__tests__/SubCalendar.spec.js
+++ b/__tests__/SubCalendar.spec.js
@@ -1,3 +1,4 @@
+const { buildParams } = require('./helpers')
 const SubCalendar = require('../lib/SubCalendar')
 const Logger = require('../lib/Logger')
 
@@ -19,9 +20,11 @@ describe('SubCalendar class', function () {
     test.each([[{ includeInactive: true }], [{ includeInactive: false }]])(
       'valid options value',
       function (options) {
+        const urlParams = buildParams(options)
         API.listSubCalendars(options)
 
         expect(Request.get).toHaveBeenCalledTimes(1)
+        expect(Request.get).toHaveBeenCalledWith(`/subcalendars?${urlParams}`)
       }
     )
 
@@ -29,32 +32,39 @@ describe('SubCalendar class', function () {
       [{ includeInactive: 'text' }],
       [{ includeInactive: [] }],
       [{ includeInactive: {} }],
+      [{ includeInactive: undefined }],
+      [{ includeInactive: 1234 }],
     ])('invalid options value', function (options) {
       expect(() => API.listSubCalendars(options)).toThrow()
     })
 
-    test.each([
-      [{}],
-      [{ includeInactive: '' }],
-      [{ includeInactive: null }],
-      [{ includeInactive: undefined }],
-      [{ includeInactive: 0 }],
-    ])('ignored options value', function (options) {
-      API.listSubCalendars(options)
+    test.each([[{}], [{ includeInactive: null }]])(
+      'ignored options value',
+      function (options) {
+        API.listSubCalendars(options)
 
-      expect(Request.get).toHaveBeenCalledTimes(1)
-    })
+        expect(Request.get).toHaveBeenCalledTimes(1)
+        expect(Request.get).toHaveBeenCalledWith('/subcalendars')
+      }
+    )
 
     test('invalid option parameter', function () {
       expect(() => API.listSubCalendars({ someKey: true })).toThrow()
     })
 
-    test.each([([], 'string', true, false, 123)])(
+    test.each([([], 'string', true, false, 123, null)])(
       'invalid options',
       function (option) {
         expect(() => API.listSubCalendars(option)).toThrow()
       }
     )
+
+    test('ignored option: undefined', function () {
+      API.listSubCalendars(undefined)
+
+      expect(Request.get).toHaveBeenCalledTimes(1)
+      expect(Request.get).toHaveBeenCalledWith('/subcalendars')
+    })
   })
 
   describe('method: listSubCalendar', function () {
@@ -62,20 +72,25 @@ describe('SubCalendar class', function () {
       API.listSubCalendar(1234)
 
       expect(Request.get).toHaveBeenCalledTimes(1)
+      expect(Request.get).toHaveBeenCalledWith('/subcalendars/1234')
     })
 
     test('with id (string)', function () {
       API.listSubCalendar('1234')
 
       expect(Request.get).toHaveBeenCalledTimes(1)
+      expect(Request.get).toHaveBeenCalledWith('/subcalendars/1234')
     })
 
     test('without id', function () {
       expect(() => API.listSubCalendar()).toThrow()
     })
 
-    test.each([[], {}, true, false, 'text'])('invalid id', function (id) {
-      expect(() => API.listSubCalendar(id)).toThrow()
-    })
+    test.each([[], {}, true, false, 'text', null, undefined])(
+      'invalid id',
+      function (id) {
+        expect(() => API.listSubCalendar(id)).toThrow()
+      }
+    )
   })
 })
diff --git a/__tests__/helpers.js b/__tests__/helpers.js
new file mode 100644
index 0000000..2fd8d23
--- /dev/null
+++ b/__tests__/helpers.js
@@ -0,0 +1,13 @@
+exports.buildParams = function (params) {
+  let urlParams = ''
+  Object.keys(params).forEach(function (key) {
+    if (key === 'subcalendarId') {
+      params[key].forEach((id) => {
+        urlParams += `${key}[]=${id}&`
+      })
+    } else {
+      urlParams += `${key}=${params[key]}&`
+    }
+  })
+  return urlParams.substring(0, urlParams.length - 1)
+}
diff --git a/examples/example.js b/examples/example.js
index 7e7a218..ba50ff5 100644
--- a/examples/example.js
+++ b/examples/example.js
@@ -9,26 +9,25 @@ const { Events, SubCalendar } = new Client({
 ;(async function getLeaves() {
   // fetch id for leave calendar
   let leaveCalId
-  await SubCalendar.listSubCalendars({ includeInactive: true }).then(
-    ({ data: { subcalendars } }) => {
+  await SubCalendar.listSubCalendars()
+    .then(({ data: { subcalendars } }) => {
       for (const subCal of subcalendars) {
         if (subCal.name === 'leave') {
           leaveCalId = subCal.id
           break
         }
       }
-    }
-  )
+    })
+    .catch((err) => console.log(err.response.data))
 
-  // get all events identified by leaveCalId
-  const {
-    data: { events },
-  } = await Events.listEvents({
-    startDate: '2022-06-06',
-    endDate: '2022-06-10',
-    subcalendarId: leaveCalId,
-  })
-
-  // leave events
-  console.log(events)
+  if (leaveCalId) {
+    // get all events identified by leaveCalId
+    await Events.listEvents({
+      startDate: '2022-06-06',
+      endDate: '2022-06-10',
+      subcalendarId: [leaveCalId],
+    })
+      .then(({ data: { events } }) => console.log(events))
+      .catch((err) => console.log(err.response.data))
+  }
 })()
diff --git a/jest.config.js b/jest.config.js
index 9a1888a..c02f013 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -3,5 +3,5 @@ module.exports = {
   clearMocks: true,
 
   // The glob patterns Jest uses to detect test files
-  testMatch: ['**/__tests__/**/*.[jt]s'],
+  testMatch: ['**/__tests__/**/*.(spec|test).[jt]s'],
 }
diff --git a/lib/API.js b/lib/API.js
index e86d8bb..03d7a7f 100644
--- a/lib/API.js
+++ b/lib/API.js
@@ -29,4 +29,22 @@ module.exports = class API {
       this._Logger.error(msg)
     }
   }
+
+  _buildUrlParams(params) {
+    let urlParams = ''
+
+    Object.keys(params).forEach((key) => {
+      if (params[key] !== null && params[key] !== undefined) {
+        if (params[key] instanceof Array) {
+          params[key].forEach((value) => {
+            urlParams += `${key}[]=${value}&`
+          })
+        } else {
+          urlParams += `${key}=${params[key]}&`
+        }
+      }
+    })
+
+    return urlParams.substring(0, urlParams.length - 1)
+  }
 }
diff --git a/lib/Client.js b/lib/Client.js
index a7a098a..4c2e512 100644
--- a/lib/Client.js
+++ b/lib/Client.js
@@ -17,7 +17,10 @@ module.exports = class Client {
   }
 
   getBaseUrl() {
-    return join(this.#url, this.#calToken)
+    return join(this.#url, this.#calToken).replace(
+      /(?<=http(s)?):\/(?!\/)/,
+      '://'
+    )
   }
 
   getAuthHeader() {
diff --git a/lib/Events.js b/lib/Events.js
index cc90c4e..86005f5 100644
--- a/lib/Events.js
+++ b/lib/Events.js
@@ -26,10 +26,8 @@ module.exports = class Events extends API {
   ) {
     this._validateOptionType(params)
 
-    const urlParams = this.#buildParams(params)
-    const path = urlParams
-      ? join(this.#ENDPOINT, `?${urlParams}`)
-      : this.#ENDPOINT
+    const urlParams = this.#getUrlParams(params)
+    const path = urlParams ? `${this.#ENDPOINT}?${urlParams}` : this.#ENDPOINT
 
     return this._Request.get(path)
   }
@@ -40,23 +38,10 @@ module.exports = class Events extends API {
     return this._Request.get(join(this.#ENDPOINT, eventId.toString()))
   }
 
-  #buildParams(params) {
+  #getUrlParams(params) {
     this.#validateParams(params)
 
-    let urlParams = ''
-    Object.keys(params).forEach((key) => {
-      if (params[key]) {
-        if (key === 'subcalendarId') {
-          params[key].forEach((id) => {
-            urlParams += `${key}[]=${id}&`
-          })
-        } else {
-          urlParams += `${key}=${params[key]}&`
-        }
-      }
-    })
-
-    return urlParams.substring(0, urlParams.length - 1)
+    return this._buildUrlParams(params)
   }
 
   #validateParams(params) {
@@ -65,29 +50,35 @@ module.exports = class Events extends API {
         this._Logger.error(`Invalid url param: '${key}'`)
       }
 
-      if (params[key]) {
-        if (
-          key === 'format' &&
-          !this.#URL_PARAMS.format.split('|').includes(params[key])
-        ) {
-          this._Logger.error(`Format can either be 'html' or 'markdown'`)
+      if (params[key] !== null) {
+        if (key === 'format') {
+          if (!this.#URL_PARAMS.format.split('|').includes(params[key])) {
+            this._Logger.error(`Format can either be 'html' or 'markdown'`)
+          }
+          return
         }
-
-        if (key !== 'format') {
-          if (key === 'subcalendarId' && !params[key] instanceof Array) {
-            this._Logger.error(
-              `Parameter '${key}' must be of type '${this.#URL_PARAMS[key]}'`
-            )
-          } else if (
-            key !== 'subcalendarId' &&
-            typeof params[key] !== this.#URL_PARAMS[key]
+        if (key === 'subcalendarId') {
+          if (
+            !(params[key] instanceof Array) ||
+            typeof params[key] == 'string'
           ) {
             this._Logger.error(
-              `Parameter '${key}' must be of type '${
-                this.#URL_PARAMS[key]
-              }'. Given '${typeof params[key]}'`
+              `Parameter '${key}' must be of type '${this.#URL_PARAMS[key]}'`
             )
           }
+          return
+        }
+        if (typeof params[key] !== this.#URL_PARAMS[key]) {
+          this._Logger.error(
+            `Parameter '${key}' must be of type '${
+              this.#URL_PARAMS[key]
+            }'. Given '${typeof params[key]}'`
+          )
+        }
+        if (key === 'startDate' || key === 'endDate') {
+          if (params[key] === '') {
+            this._Logger.error(`Invalid date for '${key}': ${params[key]}`)
+          }
         }
       }
     })
diff --git a/lib/SubCalendar.js b/lib/SubCalendar.js
index 1e7c3c4..8b21e21 100644
--- a/lib/SubCalendar.js
+++ b/lib/SubCalendar.js
@@ -18,10 +18,8 @@ module.exports = class SubCalendar extends API {
   ) {
     this._validateOptionType(params)
 
-    const urlParams = this.#buildParams(params)
-    const path = urlParams
-      ? join(this.#ENDPOINT, `?${urlParams}`)
-      : this.#ENDPOINT
+    const urlParams = this.#getUrlParams(params)
+    const path = urlParams ? `${this.#ENDPOINT}?${urlParams}` : this.#ENDPOINT
 
     return this._Request.get(path)
   }
@@ -32,14 +30,10 @@ module.exports = class SubCalendar extends API {
     return this._Request.get(join(this.#ENDPOINT, calendarId.toString()))
   }
 
-  #buildParams(params) {
+  #getUrlParams(params) {
     this.#validateParams(params)
 
-    let urlParams = params.includeInactive
-      ? `includeInactive:${params.includeInactive}`
-      : ''
-
-    return urlParams
+    return this._buildUrlParams(params)
   }
 
   #validateParams(params) {
@@ -48,7 +42,7 @@ module.exports = class SubCalendar extends API {
         this._Logger.error(`Invalid url param: '${key}'`)
       }
 
-      if (params[key]) {
+      if (params[key] !== null) {
         if (typeof params[key] !== this.#URL_PARAMS[key]) {
           this._Logger.error(
             `Parameter '${key}' must be of type '${
diff --git a/package.json b/package.json
index 3dbfee6..7741188 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@sawjan/teamup-client",
   "description": "Simple client for Teamup calendar API",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "main": "./lib/index.js",
   "author": "Sawjan G. <saw.jan.grg3e@gmail.com> (https://sajang.com.np)",
   "license": "MIT",