diff --git a/dist/firestore.js b/dist/firestore.js
new file mode 100644
index 0000000..dac5d94
--- /dev/null
+++ b/dist/firestore.js
@@ -0,0 +1,142 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.backupRootCollections = exports.backupCollection = exports.backupDocument = exports.constructDocumentValue = exports.constructReferenceUrl = undefined;
+
+var _types = require('./types');
+
+var _utility = require('./utility');
+
+var _fs = require('fs');
+
+var _fs2 = _interopRequireDefault(_fs);
+
+var _mkdirp = require('mkdirp');
+
+var _mkdirp2 = _interopRequireDefault(_mkdirp);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
+
+var constructReferenceUrl = exports.constructReferenceUrl = function constructReferenceUrl(reference) {
+  var referencePath = '';
+  Object.keys(reference).forEach(function (key) {
+    Object.keys(reference[key]).forEach(function (subKey) {
+      if (subKey === 'segments') {
+        var pathArray = reference[key][subKey];
+        pathArray.forEach(function (pathKey) {
+          referencePath = referencePath ? referencePath + '/' + pathKey : pathKey;
+        });
+      }
+    });
+  });
+  return referencePath ? { value: referencePath, typeof: 'reference' } : referencePath;
+};
+
+var constructDocumentValue = exports.constructDocumentValue = function constructDocumentValue() {
+  var documentDataToStore = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {};
+  var keys = arguments[1];
+  var documentData = arguments[2];
+
+  keys.forEach(function (key) {
+    // Boolean - boolean
+    // Reference - reference
+    // Integer - number
+    // Array - array
+    // Object - object
+    // Float - number
+    // Geographical Point - todo
+    // Map = todo
+    // Null - null
+    // String - string
+    if ((0, _types.isBoolean)(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, (0, _types.isBoolean)(documentData[key])));
+    } else if ((0, _types.isDate)(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, (0, _types.isDate)(documentData[key])));
+    } else if ((0, _types.isNumber)(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, (0, _types.isNumber)(documentData[key])));
+    } else if ((0, _types.isArray)(documentData[key])) {
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'array' });
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]));
+    } else if ((0, _types.isObject)(documentData[key])) {
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'object' });
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]));
+    } else if ((0, _types.isNull)(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, (0, _types.isNull)(documentData[key])));
+    } else if ((0, _types.isString)(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, (0, _types.isString)(documentData[key])));
+    } else {
+      documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, constructReferenceUrl(documentData[key])));
+    }
+  });
+  return documentDataToStore;
+};
+
+var backupDocument = exports.backupDocument = function backupDocument(document, backupPath, logPath, prettyPrintJSON) {
+  console.log('Backing up Document \'' + logPath + document.id + '\'');
+  try {
+    _mkdirp2.default.sync(backupPath);
+  } catch (error) {
+    throw new Error('Unable to create backup path for Document \'' + document.id + '\': ' + error);
+  }
+
+  var fileContents = void 0;
+  try {
+    var documentData = document.data();
+    var keys = Object.keys(documentData);
+    var documentDataToStore = {};
+    documentDataToStore = Object.assign({}, constructDocumentValue(documentDataToStore, keys, documentData));
+    if (prettyPrintJSON === true) {
+      fileContents = JSON.stringify(documentDataToStore, null, 2);
+    } else {
+      fileContents = JSON.stringify(documentDataToStore);
+    }
+  } catch (error) {
+    throw new Error('Unable to serialize Document \'' + document.id + '\': ' + error);
+  }
+  try {
+    _fs2.default.writeFileSync(backupPath + '/' + document.id + '.json', fileContents);
+  } catch (error) {
+    throw new Error('Unable to write Document \'' + document.id + '\': ' + error);
+  }
+
+  return document.ref.getCollections().then(function (collections) {
+    return (0, _utility.promiseSerial)(collections.map(function (collection) {
+      return function () {
+        return backupCollection(collection, backupPath + '/' + collection.id, logPath + document.id + '/', prettyPrintJSON);
+      };
+    }));
+  });
+};
+
+var backupCollection = exports.backupCollection = function backupCollection(collection, backupPath, logPath, prettyPrintJSON) {
+  console.log('Backing up Collection \'' + logPath + collection.id + '\'');
+  try {
+    _mkdirp2.default.sync(backupPath);
+  } catch (error) {
+    throw new Error('Unable to create backup path for Collection \'' + collection.id + '\': ' + error);
+  }
+
+  return collection.get().then(function (documentSnapshots) {
+    var backupFunctions = [];
+    documentSnapshots.forEach(function (document) {
+      backupFunctions.push(function () {
+        return backupDocument(document, backupPath + '/' + document.id, logPath + collection.id + '/', prettyPrintJSON);
+      });
+    });
+    return (0, _utility.promiseSerial)(backupFunctions);
+  });
+};
+
+var backupRootCollections = exports.backupRootCollections = function backupRootCollections(database, backupPath, prettyPrintJSON) {
+  return database.getCollections().then(function (collections) {
+    return (0, _utility.promiseSerial)(collections.map(function (collection) {
+      return function () {
+        return backupCollection(collection, backupPath + '/' + collection.id, '/', prettyPrintJSON);
+      };
+    }));
+  });
+};
\ No newline at end of file
diff --git a/dist/firestore.js.flow b/dist/firestore.js.flow
new file mode 100644
index 0000000..6bdd563
--- /dev/null
+++ b/dist/firestore.js.flow
@@ -0,0 +1,124 @@
+/* @flow */
+
+import { isString, isNull, isObject, isArray, isNumber, isDate, isBoolean } from './types'
+import { promiseSerial } from './utility'
+
+import fs from 'fs'
+import mkdirp from 'mkdirp'
+
+export const constructReferenceUrl = (reference: Object) => {
+  var referencePath = ''
+  Object.keys(reference).forEach(key => {
+    Object.keys(reference[key]).forEach(subKey => {
+      if (subKey === 'segments') {
+        const pathArray = reference[key][subKey]
+        pathArray.forEach(pathKey => { referencePath = referencePath ? `${referencePath}/${pathKey}` : pathKey })
+      }
+    })
+  })
+  return referencePath ? { value: referencePath, typeof: 'reference' } : referencePath
+}
+
+export const constructDocumentValue = (documentDataToStore: Object = {}, keys: Array<string>, documentData: Object) => {
+  keys.forEach(key => {
+    // Boolean - boolean
+    // Reference - reference
+    // Integer - number
+    // Array - array
+    // Object - object
+    // Float - number
+    // Geographical Point - todo
+    // Map = todo
+    // Null - null
+    // String - string
+    if (isBoolean(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isBoolean(documentData[key]) })
+    } else if (isDate(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isDate(documentData[key]) })
+    } else if (isNumber(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isNumber(documentData[key]) })
+    } else if (isArray(documentData[key])) {
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'array' })
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]))
+    } else if (isObject(documentData[key])) {
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'object' })
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]))
+    } else if (isNull(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isNull(documentData[key]) })
+    } else if (isString(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isString(documentData[key]) })
+    } else {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: constructReferenceUrl(documentData[key]) })
+    }
+  })
+  return documentDataToStore
+}
+
+export const backupDocument = (document: Object, backupPath: string, logPath: string, prettyPrintJSON: boolean) => {
+  console.log('Backing up Document \'' + logPath + document.id + '\'')
+  try {
+    mkdirp.sync(backupPath)
+  } catch (error) {
+    throw new Error('Unable to create backup path for Document \'' + document.id + '\': ' + error)
+  }
+
+  let fileContents: string
+  try {
+    const documentData = document.data()
+    const keys = Object.keys(documentData)
+    var documentDataToStore = {}
+    documentDataToStore = Object.assign({}, constructDocumentValue(documentDataToStore, keys, documentData))
+    if (prettyPrintJSON === true) {
+      fileContents = JSON.stringify(documentDataToStore, null, 2)
+    } else {
+      fileContents = JSON.stringify(documentDataToStore)
+    }
+  } catch (error) {
+    throw new Error('Unable to serialize Document \'' + document.id + '\': ' + error)
+  }
+  try {
+    fs.writeFileSync(backupPath + '/' + document.id + '.json', fileContents)
+  } catch (error) {
+    throw new Error('Unable to write Document \'' + document.id + '\': ' + error)
+  }
+
+  return document.ref.getCollections()
+    .then((collections) => {
+      return promiseSerial(collections.map((collection) => {
+        return () => {
+          return backupCollection(collection, backupPath + '/' + collection.id, logPath + document.id + '/', prettyPrintJSON)
+        }
+      }))
+    })
+}
+
+export const backupCollection = (collection: Object, backupPath: string, logPath: string, prettyPrintJSON: boolean) => {
+  console.log('Backing up Collection \'' + logPath + collection.id + '\'')
+  try {
+    mkdirp.sync(backupPath)
+  } catch (error) {
+    throw new Error('Unable to create backup path for Collection \'' + collection.id + '\': ' + error)
+  }
+
+  return collection.get()
+    .then((documentSnapshots) => {
+      const backupFunctions = []
+      documentSnapshots.forEach((document) => {
+        backupFunctions.push(() => {
+          return backupDocument(document, backupPath + '/' + document.id, logPath + collection.id + '/', prettyPrintJSON)
+        })
+      })
+      return promiseSerial(backupFunctions)
+    })
+}
+
+export const backupRootCollections = (database: Object, backupPath: string, prettyPrintJSON: boolean) => {
+  return database.getCollections()
+    .then((collections) => {
+      return promiseSerial(collections.map((collection) => {
+        return () => {
+          return backupCollection(collection, backupPath + '/' + collection.id, '/', prettyPrintJSON)
+        }
+      }))
+    })
+}
diff --git a/dist/index.js b/dist/index.js
index aa154c3..980bea3 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -7,225 +7,6 @@ Object.defineProperty(exports, "__esModule", {
 var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };
 
 exports.default = function (accountCredentials, backupPath, prettyPrintJSON) {
-  // Returns if a value is a string
-  var isString = function isString(value) {
-    if (typeof value === 'string' || value instanceof String) {
-      return {
-        value: value,
-        typeof: 'string'
-      };
-    }
-    return false;
-  };
-
-  // Returns if a value is really a number
-  var isNumber = function isNumber(value) {
-    if (typeof value === 'number' && isFinite(value)) {
-      return {
-        value: value,
-        typeof: 'number'
-      };
-    }
-    return false;
-  };
-
-  // Returns if a value is an array
-  var isArray = function isArray(value) {
-    if (value && (typeof value === 'undefined' ? 'undefined' : _typeof(value)) === 'object' && value.constructor === Array) {
-      return {
-        value: value,
-        typeof: 'array'
-      };
-    }
-    return false;
-  };
-
-  // Returns if a value is an object
-  var isObject = function isObject(value) {
-    if (value && (typeof value === 'undefined' ? 'undefined' : _typeof(value)) === 'object' && value.constructor === Object) {
-      return {
-        value: value,
-        typeof: 'object'
-      };
-    }
-    return false;
-  };
-
-  // Returns if a value is null
-  var isNull = function isNull(value) {
-    if (value === null) {
-      return {
-        value: value,
-        typeof: 'null'
-      };
-    }
-    return false;
-  };
-
-  // Returns if a value is undefined
-  var isUndefined = function isUndefined(value) {
-    if (typeof value === 'undefined') {
-      return {
-        value: value,
-        typeof: 'undefined'
-      };
-    }
-    return false;
-  };
-
-  // Returns if a value is a boolean
-  var isBoolean = function isBoolean(value) {
-    if (typeof value === 'boolean') {
-      return {
-        value: value,
-        typeof: 'boolean'
-      };
-    }
-    return false;
-  };
-
-  // Returns if value is a date object
-  var isDate = function isDate(value) {
-    if (value instanceof Date) {
-      return {
-        value: value,
-        typeof: 'date'
-      };
-    }
-    return false;
-  };
-
-  var constructReferenceUrl = function constructReferenceUrl(reference) {
-    var referencePath = '';
-    Object.keys(reference).forEach(function (key) {
-      Object.keys(reference[key]).forEach(function (subKey) {
-        if (subKey === 'segments') {
-          var pathArray = reference[key][subKey];
-          pathArray.forEach(function (pathKey) {
-            referencePath = referencePath ? referencePath + '/' + pathKey : pathKey;
-          });
-        }
-      });
-    });
-    return referencePath ? { value: referencePath, typeof: 'reference' } : referencePath;
-  };
-
-  var constructDocumentValue = function constructDocumentValue() {
-    var documentDataToStore = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {};
-    var keys = arguments[1];
-    var documentData = arguments[2];
-
-    keys.forEach(function (key) {
-      // Boolean - boolean
-      // Reference - reference
-      // Integer - number
-      // Array - array
-      // Object - object
-      // Float - number
-      // Geographical Point - todo
-      // Map = todo
-      // Null - null
-      // String - string
-      if (isBoolean(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, isBoolean(documentData[key])));
-      } else if (isDate(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, isDate(documentData[key])));
-      } else if (isNumber(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, isNumber(documentData[key])));
-      } else if (isArray(documentData[key])) {
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'array' });
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]));
-      } else if (isObject(documentData[key])) {
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'object' });
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]));
-      } else if (isNull(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, isNull(documentData[key])));
-      } else if (isString(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, isString(documentData[key])));
-      } else {
-        documentDataToStore = Object.assign({}, documentDataToStore, _defineProperty({}, key, constructReferenceUrl(documentData[key])));
-      }
-    });
-    return documentDataToStore;
-  };
-
-  // from: https://hackernoon.com/functional-javascript-resolving-promises-sequentially-7aac18c4431e
-  var promiseSerial = function promiseSerial(funcs) {
-    return funcs.reduce(function (promise, func) {
-      return promise.then(function (result) {
-        return func().then(function () {
-          return Array.prototype.concat.bind(result);
-        });
-      });
-    }, Promise.resolve([]));
-  };
-
-  var backupDocument = function backupDocument(document, backupPath, logPath) {
-    console.log('Backing up Document \'' + logPath + document.id + '\'');
-    try {
-      _mkdirp2.default.sync(backupPath);
-    } catch (error) {
-      throw new Error('Unable to create backup path for Document \'' + document.id + '\': ' + error);
-    }
-
-    var fileContents = void 0;
-    try {
-      var documentData = document.data();
-      var keys = Object.keys(documentData);
-      var documentDataToStore = {};
-      documentDataToStore = Object.assign({}, constructDocumentValue(documentDataToStore, keys, documentData));
-      if (prettyPrintJSON === true) {
-        fileContents = JSON.stringify(documentDataToStore, null, 2);
-      } else {
-        fileContents = JSON.stringify(documentDataToStore);
-      }
-    } catch (error) {
-      throw new Error('Unable to serialize Document \'' + document.id + '\': ' + error);
-    }
-    try {
-      _fs2.default.writeFileSync(backupPath + '/' + document.id + '.json', fileContents);
-    } catch (error) {
-      throw new Error('Unable to write Document \'' + document.id + '\': ' + error);
-    }
-
-    return document.ref.getCollections().then(function (collections) {
-      return promiseSerial(collections.map(function (collection) {
-        return function () {
-          return backupCollection(collection, backupPath + '/' + collection.id, logPath + document.id + '/');
-        };
-      }));
-    });
-  };
-
-  var backupCollection = function backupCollection(collection, backupPath, logPath) {
-    console.log('Backing up Collection \'' + logPath + collection.id + '\'');
-    try {
-      _mkdirp2.default.sync(backupPath);
-    } catch (error) {
-      throw new Error('Unable to create backup path for Collection \'' + collection.id + '\': ' + error);
-    }
-
-    return collection.get().then(function (documentSnapshots) {
-      var backupFunctions = [];
-      documentSnapshots.forEach(function (document) {
-        backupFunctions.push(function () {
-          return backupDocument(document, backupPath + '/' + document.id, logPath + collection.id + '/');
-        });
-      });
-      return promiseSerial(backupFunctions);
-    });
-  };
-
-  var backupRootCollections = function backupRootCollections(database) {
-    return database.getCollections().then(function (collections) {
-      return promiseSerial(collections.map(function (collection) {
-        return function () {
-          return backupCollection(collection, backupPath + '/' + collection.id, '/');
-        };
-      }));
-    });
-  };
-
   var accountCredentialsContents = void 0;
   if (typeof accountCredentials === 'string') {
     try {
@@ -251,7 +32,7 @@ exports.default = function (accountCredentials, backupPath, prettyPrintJSON) {
   }
 
   var database = _firebaseAdmin2.default.firestore();
-  return backupRootCollections(database);
+  return (0, _firestore.backupRootCollections)(database, backupPath, prettyPrintJSON);
 };
 
 var _firebaseAdmin = require('firebase-admin');
@@ -266,6 +47,6 @@ var _mkdirp = require('mkdirp');
 
 var _mkdirp2 = _interopRequireDefault(_mkdirp);
 
-function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+var _firestore = require('./firestore');
 
-function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
\ No newline at end of file
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
\ No newline at end of file
diff --git a/dist/index.js.flow b/dist/index.js.flow
index 07174a4..77dc996 100644
--- a/dist/index.js.flow
+++ b/dist/index.js.flow
@@ -5,224 +5,9 @@ import Firebase from 'firebase-admin'
 import fs from 'fs'
 import mkdirp from 'mkdirp'
 
-export default function (accountCredentials: string | Object, backupPath: string, prettyPrintJSON: boolean) {
-  // Returns if a value is a string
-  const isString = (value) => {
-    if (typeof value === 'string' || value instanceof String) {
-      return {
-        value,
-        typeof: 'string'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is really a number
-  const isNumber = (value) => {
-    if (typeof value === 'number' && isFinite(value)) {
-      return {
-        value,
-        typeof: 'number'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is an array
-  const isArray = (value) => {
-    if (value && typeof value === 'object' && value.constructor === Array) {
-      return {
-        value,
-        typeof: 'array'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is an object
-  const isObject = (value) => {
-    if (value && typeof value === 'object' && value.constructor === Object) {
-      return {
-        value,
-        typeof: 'object'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is null
-  const isNull = (value) => {
-    if (value === null) {
-      return {
-        value,
-        typeof: 'null'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is undefined
-  const isUndefined = (value) => {
-    if (typeof value === 'undefined') {
-      return {
-        value,
-        typeof: 'undefined'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is a boolean
-  const isBoolean = (value) => {
-    if (typeof value === 'boolean') {
-      return {
-        value,
-        typeof: 'boolean'
-      }
-    }
-    return false
-  }
-
-  // Returns if value is a date object
-  const isDate = (value) => {
-    if (value instanceof Date) {
-      return {
-        value,
-        typeof: 'date'
-      }
-    }
-    return false
-  }
-
-  const constructReferenceUrl = (reference) => {
-    var referencePath = ''
-    Object.keys(reference).forEach(key => {
-      Object.keys(reference[key]).forEach(subKey => {
-        if (subKey === 'segments') {
-          const pathArray = reference[key][subKey]
-          pathArray.forEach(pathKey => { referencePath = referencePath ? `${referencePath}/${pathKey}` : pathKey })
-        }
-      })
-    })
-    return referencePath ? { value: referencePath, typeof: 'reference' } : referencePath
-  }
-
-  const constructDocumentValue = (documentDataToStore = {}, keys, documentData) => {
-    keys.forEach(key => {
-      // Boolean - boolean
-      // Reference - reference
-      // Integer - number
-      // Array - array
-      // Object - object
-      // Float - number
-      // Geographical Point - todo
-      // Map = todo
-      // Null - null
-      // String - string
-      if (isBoolean(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isBoolean(documentData[key]) })
-      } else if (isDate(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isDate(documentData[key]) })
-      } else if (isNumber(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isNumber(documentData[key]) })
-      } else if (isArray(documentData[key])) {
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'array' })
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]))
-      } else if (isObject(documentData[key])) {
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'object' })
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]))
-      } else if (isNull(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isNull(documentData[key]) })
-      } else if (isString(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isString(documentData[key]) })
-      } else {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: constructReferenceUrl(documentData[key]) })
-      }
-    })
-    return documentDataToStore
-  }
-
-  // from: https://hackernoon.com/functional-javascript-resolving-promises-sequentially-7aac18c4431e
-  const promiseSerial = (funcs) => {
-    return funcs.reduce(
-      (promise, func) => {
-        return promise.then((result) => {
-          return func().then(() => {
-            return Array.prototype.concat.bind(result)
-          })
-        })
-      }, Promise.resolve([]))
-  }
-
-  const backupDocument = (document: Object, backupPath: string, logPath: string) => {
-    console.log('Backing up Document \'' + logPath + document.id + '\'')
-    try {
-      mkdirp.sync(backupPath)
-    } catch (error) {
-      throw new Error('Unable to create backup path for Document \'' + document.id + '\': ' + error)
-    }
-
-    let fileContents: string
-    try {
-      const documentData = document.data()
-      const keys = Object.keys(documentData)
-      var documentDataToStore = {}
-      documentDataToStore = Object.assign({}, constructDocumentValue(documentDataToStore, keys, documentData))
-      if (prettyPrintJSON === true) {
-        fileContents = JSON.stringify(documentDataToStore, null, 2)
-      } else {
-        fileContents = JSON.stringify(documentDataToStore)
-      }
-    } catch (error) {
-      throw new Error('Unable to serialize Document \'' + document.id + '\': ' + error)
-    }
-    try {
-      fs.writeFileSync(backupPath + '/' + document.id + '.json', fileContents)
-    } catch (error) {
-      throw new Error('Unable to write Document \'' + document.id + '\': ' + error)
-    }
-
-    return document.ref.getCollections()
-      .then((collections) => {
-        return promiseSerial(collections.map((collection) => {
-          return () => {
-            return backupCollection(collection, backupPath + '/' + collection.id, logPath + document.id + '/')
-          }
-        }))
-      })
-  }
-
-  const backupCollection = (collection: Object, backupPath: string, logPath: string) => {
-    console.log('Backing up Collection \'' + logPath + collection.id + '\'')
-    try {
-      mkdirp.sync(backupPath)
-    } catch (error) {
-      throw new Error('Unable to create backup path for Collection \'' + collection.id + '\': ' + error)
-    }
-
-    return collection.get()
-      .then((documentSnapshots) => {
-        const backupFunctions = []
-        documentSnapshots.forEach((document) => {
-          backupFunctions.push(() => {
-            return backupDocument(document, backupPath + '/' + document.id, logPath + collection.id + '/')
-          })
-        })
-        return promiseSerial(backupFunctions)
-      })
-  }
-
-  const backupRootCollections = (database: Object) => {
-    return database.getCollections()
-      .then((collections) => {
-        return promiseSerial(collections.map((collection) => {
-          return () => {
-            return backupCollection(collection, backupPath + '/' + collection.id, '/')
-          }
-        }))
-      })
-  }
+import { backupRootCollections } from './firestore'
 
+export default function (accountCredentials: string | Object, backupPath: string, prettyPrintJSON: boolean) {
   let accountCredentialsContents: Object
   if (typeof accountCredentials === 'string') {
     try {
@@ -248,5 +33,5 @@ export default function (accountCredentials: string | Object, backupPath: string
   }
 
   const database = Firebase.firestore()
-  return backupRootCollections(database)
+  return backupRootCollections(database, backupPath, prettyPrintJSON)
 }
diff --git a/dist/types.js b/dist/types.js
new file mode 100644
index 0000000..4161b0a
--- /dev/null
+++ b/dist/types.js
@@ -0,0 +1,95 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+
+var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };
+
+// Returns if a value is a string
+var isString = exports.isString = function isString(value) {
+  if (typeof value === 'string' || value instanceof String) {
+    return {
+      value: value,
+      type: 'string'
+    };
+  }
+  return false;
+};
+
+// Returns if a value is really a number
+var isNumber = exports.isNumber = function isNumber(value) {
+  if (typeof value === 'number' && isFinite(value)) {
+    return {
+      value: value,
+      type: 'number'
+    };
+  }
+  return false;
+};
+
+// Returns if a value is an array
+var isArray = exports.isArray = function isArray(value) {
+  if (value && (typeof value === 'undefined' ? 'undefined' : _typeof(value)) === 'object' && value.constructor === Array) {
+    return {
+      value: value,
+      type: 'array'
+    };
+  }
+  return false;
+};
+
+// Returns if a value is an object
+var isObject = exports.isObject = function isObject(value) {
+  if (value && (typeof value === 'undefined' ? 'undefined' : _typeof(value)) === 'object' && value.constructor === Object) {
+    return {
+      value: value,
+      type: 'object'
+    };
+  }
+  return false;
+};
+
+// Returns if a value is null
+var isNull = exports.isNull = function isNull(value) {
+  if (value === null) {
+    return {
+      value: value,
+      type: 'null'
+    };
+  }
+  return false;
+};
+
+// Returns if a value is undefined
+var isUndefined = exports.isUndefined = function isUndefined(value) {
+  if (typeof value === 'undefined') {
+    return {
+      value: value,
+      type: 'undefined'
+    };
+  }
+  return false;
+};
+
+// Returns if a value is a boolean
+var isBoolean = exports.isBoolean = function isBoolean(value) {
+  if (typeof value === 'boolean') {
+    return {
+      value: value,
+      type: 'boolean'
+    };
+  }
+  return false;
+};
+
+// Returns if value is a date object
+var isDate = exports.isDate = function isDate(value) {
+  if (value instanceof Date) {
+    return {
+      value: value,
+      type: 'date'
+    };
+  }
+  return false;
+};
\ No newline at end of file
diff --git a/dist/types.js.flow b/dist/types.js.flow
new file mode 100644
index 0000000..43c819e
--- /dev/null
+++ b/dist/types.js.flow
@@ -0,0 +1,96 @@
+/* @flow */
+
+export type ValueDescription = {
+    value: any,
+    type: string
+}
+
+export type ValidationResult = ValueDescription | false;
+
+// Returns if a value is a string
+export const isString = (value: any): ValidationResult => {
+  if (typeof value === 'string' || value instanceof String) {
+    return {
+      value,
+      type: 'string'
+    }
+  }
+  return false
+}
+
+// Returns if a value is really a number
+export const isNumber = (value: any): ValidationResult => {
+  if (typeof value === 'number' && isFinite(value)) {
+    return {
+      value,
+      type: 'number'
+    }
+  }
+  return false
+}
+
+// Returns if a value is an array
+export const isArray = (value: any): ValidationResult => {
+  if (value && typeof value === 'object' && value.constructor === Array) {
+    return {
+      value,
+      type: 'array'
+    }
+  }
+  return false
+}
+
+// Returns if a value is an object
+export const isObject = (value: any): ValidationResult => {
+  if (value && typeof value === 'object' && value.constructor === Object) {
+    return {
+      value,
+      type: 'object'
+    }
+  }
+  return false
+}
+
+// Returns if a value is null
+export const isNull = (value: any): ValidationResult => {
+  if (value === null) {
+    return {
+      value,
+      type: 'null'
+    }
+  }
+  return false
+}
+
+// Returns if a value is undefined
+export const isUndefined = (value: any): ValidationResult => {
+  if (typeof value === 'undefined') {
+    return {
+      value,
+      type: 'undefined'
+    }
+  }
+  return false
+}
+
+// Returns if a value is a boolean
+export const isBoolean = (value: any): ValidationResult => {
+  if (typeof value === 'boolean') {
+    return {
+      value,
+      type: 'boolean'
+    }
+  }
+  return false
+}
+
+// Returns if value is a date object
+export const isDate = (value: any): ValidationResult => {
+  if (value instanceof Date) {
+    return {
+      value,
+      type: 'date'
+    }
+  }
+  return false
+}
diff --git a/dist/utility.js b/dist/utility.js
new file mode 100644
index 0000000..72508a6
--- /dev/null
+++ b/dist/utility.js
@@ -0,0 +1,16 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+// TODO: Flow coverage
+// from: https://hackernoon.com/functional-javascript-resolving-promises-sequentially-7aac18c4431e
+var promiseSerial = exports.promiseSerial = function promiseSerial(funcs) {
+  return funcs.reduce(function (promise, func) {
+    return promise.then(function (result) {
+      return func().then(function () {
+        return Array.prototype.concat.bind(result);
+      });
+    });
+  }, Promise.resolve([]));
+};
\ No newline at end of file
diff --git a/dist/utility.js.flow b/dist/utility.js.flow
new file mode 100644
index 0000000..134ccd7
--- /dev/null
+++ b/dist/utility.js.flow
@@ -0,0 +1,12 @@
+// TODO: Flow coverage
+// from: https://hackernoon.com/functional-javascript-resolving-promises-sequentially-7aac18c4431e
+export const promiseSerial = (funcs) => {
+  return funcs.reduce(
+    (promise, func) => {
+      return promise.then((result) => {
+        return func().then(() => {
+          return Array.prototype.concat.bind(result)
+        })
+      })
+    }, Promise.resolve([]))
+}
diff --git a/lib/firestore.js b/lib/firestore.js
new file mode 100644
index 0000000..6bdd563
--- /dev/null
+++ b/lib/firestore.js
@@ -0,0 +1,124 @@
+/* @flow */
+
+import { isString, isNull, isObject, isArray, isNumber, isDate, isBoolean } from './types'
+import { promiseSerial } from './utility'
+
+import fs from 'fs'
+import mkdirp from 'mkdirp'
+
+export const constructReferenceUrl = (reference: Object) => {
+  var referencePath = ''
+  Object.keys(reference).forEach(key => {
+    Object.keys(reference[key]).forEach(subKey => {
+      if (subKey === 'segments') {
+        const pathArray = reference[key][subKey]
+        pathArray.forEach(pathKey => { referencePath = referencePath ? `${referencePath}/${pathKey}` : pathKey })
+      }
+    })
+  })
+  return referencePath ? { value: referencePath, typeof: 'reference' } : referencePath
+}
+
+export const constructDocumentValue = (documentDataToStore: Object = {}, keys: Array<string>, documentData: Object) => {
+  keys.forEach(key => {
+    // Boolean - boolean
+    // Reference - reference
+    // Integer - number
+    // Array - array
+    // Object - object
+    // Float - number
+    // Geographical Point - todo
+    // Map = todo
+    // Null - null
+    // String - string
+    if (isBoolean(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isBoolean(documentData[key]) })
+    } else if (isDate(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isDate(documentData[key]) })
+    } else if (isNumber(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isNumber(documentData[key]) })
+    } else if (isArray(documentData[key])) {
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'array' })
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]))
+    } else if (isObject(documentData[key])) {
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'object' })
+      documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]))
+    } else if (isNull(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isNull(documentData[key]) })
+    } else if (isString(documentData[key])) {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isString(documentData[key]) })
+    } else {
+      documentDataToStore = Object.assign({}, documentDataToStore, { [key]: constructReferenceUrl(documentData[key]) })
+    }
+  })
+  return documentDataToStore
+}
+
+export const backupDocument = (document: Object, backupPath: string, logPath: string, prettyPrintJSON: boolean) => {
+  console.log('Backing up Document \'' + logPath + document.id + '\'')
+  try {
+    mkdirp.sync(backupPath)
+  } catch (error) {
+    throw new Error('Unable to create backup path for Document \'' + document.id + '\': ' + error)
+  }
+
+  let fileContents: string
+  try {
+    const documentData = document.data()
+    const keys = Object.keys(documentData)
+    var documentDataToStore = {}
+    documentDataToStore = Object.assign({}, constructDocumentValue(documentDataToStore, keys, documentData))
+    if (prettyPrintJSON === true) {
+      fileContents = JSON.stringify(documentDataToStore, null, 2)
+    } else {
+      fileContents = JSON.stringify(documentDataToStore)
+    }
+  } catch (error) {
+    throw new Error('Unable to serialize Document \'' + document.id + '\': ' + error)
+  }
+  try {
+    fs.writeFileSync(backupPath + '/' + document.id + '.json', fileContents)
+  } catch (error) {
+    throw new Error('Unable to write Document \'' + document.id + '\': ' + error)
+  }
+
+  return document.ref.getCollections()
+    .then((collections) => {
+      return promiseSerial(collections.map((collection) => {
+        return () => {
+          return backupCollection(collection, backupPath + '/' + collection.id, logPath + document.id + '/', prettyPrintJSON)
+        }
+      }))
+    })
+}
+
+export const backupCollection = (collection: Object, backupPath: string, logPath: string, prettyPrintJSON: boolean) => {
+  console.log('Backing up Collection \'' + logPath + collection.id + '\'')
+  try {
+    mkdirp.sync(backupPath)
+  } catch (error) {
+    throw new Error('Unable to create backup path for Collection \'' + collection.id + '\': ' + error)
+  }
+
+  return collection.get()
+    .then((documentSnapshots) => {
+      const backupFunctions = []
+      documentSnapshots.forEach((document) => {
+        backupFunctions.push(() => {
+          return backupDocument(document, backupPath + '/' + document.id, logPath + collection.id + '/', prettyPrintJSON)
+        })
+      })
+      return promiseSerial(backupFunctions)
+    })
+}
+
+export const backupRootCollections = (database: Object, backupPath: string, prettyPrintJSON: boolean) => {
+  return database.getCollections()
+    .then((collections) => {
+      return promiseSerial(collections.map((collection) => {
+        return () => {
+          return backupCollection(collection, backupPath + '/' + collection.id, '/', prettyPrintJSON)
+        }
+      }))
+    })
+}
diff --git a/lib/index.js b/lib/index.js
index 07174a4..77dc996 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -5,224 +5,9 @@ import Firebase from 'firebase-admin'
 import fs from 'fs'
 import mkdirp from 'mkdirp'
 
-export default function (accountCredentials: string | Object, backupPath: string, prettyPrintJSON: boolean) {
-  // Returns if a value is a string
-  const isString = (value) => {
-    if (typeof value === 'string' || value instanceof String) {
-      return {
-        value,
-        typeof: 'string'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is really a number
-  const isNumber = (value) => {
-    if (typeof value === 'number' && isFinite(value)) {
-      return {
-        value,
-        typeof: 'number'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is an array
-  const isArray = (value) => {
-    if (value && typeof value === 'object' && value.constructor === Array) {
-      return {
-        value,
-        typeof: 'array'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is an object
-  const isObject = (value) => {
-    if (value && typeof value === 'object' && value.constructor === Object) {
-      return {
-        value,
-        typeof: 'object'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is null
-  const isNull = (value) => {
-    if (value === null) {
-      return {
-        value,
-        typeof: 'null'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is undefined
-  const isUndefined = (value) => {
-    if (typeof value === 'undefined') {
-      return {
-        value,
-        typeof: 'undefined'
-      }
-    }
-    return false
-  }
-
-  // Returns if a value is a boolean
-  const isBoolean = (value) => {
-    if (typeof value === 'boolean') {
-      return {
-        value,
-        typeof: 'boolean'
-      }
-    }
-    return false
-  }
-
-  // Returns if value is a date object
-  const isDate = (value) => {
-    if (value instanceof Date) {
-      return {
-        value,
-        typeof: 'date'
-      }
-    }
-    return false
-  }
-
-  const constructReferenceUrl = (reference) => {
-    var referencePath = ''
-    Object.keys(reference).forEach(key => {
-      Object.keys(reference[key]).forEach(subKey => {
-        if (subKey === 'segments') {
-          const pathArray = reference[key][subKey]
-          pathArray.forEach(pathKey => { referencePath = referencePath ? `${referencePath}/${pathKey}` : pathKey })
-        }
-      })
-    })
-    return referencePath ? { value: referencePath, typeof: 'reference' } : referencePath
-  }
-
-  const constructDocumentValue = (documentDataToStore = {}, keys, documentData) => {
-    keys.forEach(key => {
-      // Boolean - boolean
-      // Reference - reference
-      // Integer - number
-      // Array - array
-      // Object - object
-      // Float - number
-      // Geographical Point - todo
-      // Map = todo
-      // Null - null
-      // String - string
-      if (isBoolean(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isBoolean(documentData[key]) })
-      } else if (isDate(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isDate(documentData[key]) })
-      } else if (isNumber(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isNumber(documentData[key]) })
-      } else if (isArray(documentData[key])) {
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'array' })
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]))
-      } else if (isObject(documentData[key])) {
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], { typeof: 'object' })
-        documentDataToStore[key] = Object.assign({}, documentDataToStore[key], constructDocumentValue({}, Object.keys(documentData[key]), documentData[key]))
-      } else if (isNull(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isNull(documentData[key]) })
-      } else if (isString(documentData[key])) {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: isString(documentData[key]) })
-      } else {
-        documentDataToStore = Object.assign({}, documentDataToStore, { [key]: constructReferenceUrl(documentData[key]) })
-      }
-    })
-    return documentDataToStore
-  }
-
-  // from: https://hackernoon.com/functional-javascript-resolving-promises-sequentially-7aac18c4431e
-  const promiseSerial = (funcs) => {
-    return funcs.reduce(
-      (promise, func) => {
-        return promise.then((result) => {
-          return func().then(() => {
-            return Array.prototype.concat.bind(result)
-          })
-        })
-      }, Promise.resolve([]))
-  }
-
-  const backupDocument = (document: Object, backupPath: string, logPath: string) => {
-    console.log('Backing up Document \'' + logPath + document.id + '\'')
-    try {
-      mkdirp.sync(backupPath)
-    } catch (error) {
-      throw new Error('Unable to create backup path for Document \'' + document.id + '\': ' + error)
-    }
-
-    let fileContents: string
-    try {
-      const documentData = document.data()
-      const keys = Object.keys(documentData)
-      var documentDataToStore = {}
-      documentDataToStore = Object.assign({}, constructDocumentValue(documentDataToStore, keys, documentData))
-      if (prettyPrintJSON === true) {
-        fileContents = JSON.stringify(documentDataToStore, null, 2)
-      } else {
-        fileContents = JSON.stringify(documentDataToStore)
-      }
-    } catch (error) {
-      throw new Error('Unable to serialize Document \'' + document.id + '\': ' + error)
-    }
-    try {
-      fs.writeFileSync(backupPath + '/' + document.id + '.json', fileContents)
-    } catch (error) {
-      throw new Error('Unable to write Document \'' + document.id + '\': ' + error)
-    }
-
-    return document.ref.getCollections()
-      .then((collections) => {
-        return promiseSerial(collections.map((collection) => {
-          return () => {
-            return backupCollection(collection, backupPath + '/' + collection.id, logPath + document.id + '/')
-          }
-        }))
-      })
-  }
-
-  const backupCollection = (collection: Object, backupPath: string, logPath: string) => {
-    console.log('Backing up Collection \'' + logPath + collection.id + '\'')
-    try {
-      mkdirp.sync(backupPath)
-    } catch (error) {
-      throw new Error('Unable to create backup path for Collection \'' + collection.id + '\': ' + error)
-    }
-
-    return collection.get()
-      .then((documentSnapshots) => {
-        const backupFunctions = []
-        documentSnapshots.forEach((document) => {
-          backupFunctions.push(() => {
-            return backupDocument(document, backupPath + '/' + document.id, logPath + collection.id + '/')
-          })
-        })
-        return promiseSerial(backupFunctions)
-      })
-  }
-
-  const backupRootCollections = (database: Object) => {
-    return database.getCollections()
-      .then((collections) => {
-        return promiseSerial(collections.map((collection) => {
-          return () => {
-            return backupCollection(collection, backupPath + '/' + collection.id, '/')
-          }
-        }))
-      })
-  }
+import { backupRootCollections } from './firestore'
 
+export default function (accountCredentials: string | Object, backupPath: string, prettyPrintJSON: boolean) {
   let accountCredentialsContents: Object
   if (typeof accountCredentials === 'string') {
     try {
@@ -248,5 +33,5 @@ export default function (accountCredentials: string | Object, backupPath: string
   }
 
   const database = Firebase.firestore()
-  return backupRootCollections(database)
+  return backupRootCollections(database, backupPath, prettyPrintJSON)
 }
diff --git a/lib/types.js b/lib/types.js
new file mode 100644
index 0000000..43c819e
--- /dev/null
+++ b/lib/types.js
@@ -0,0 +1,96 @@
+/* @flow */
+
+export type ValueDescription = {
+    value: any,
+    type: string
+}
+
+export type ValidationResult = ValueDescription | false;
+
+// Returns if a value is a string
+export const isString = (value: any): ValidationResult => {
+  if (typeof value === 'string' || value instanceof String) {
+    return {
+      value,
+      type: 'string'
+    }
+  }
+  return false
+}
+
+// Returns if a value is really a number
+export const isNumber = (value: any): ValidationResult => {
+  if (typeof value === 'number' && isFinite(value)) {
+    return {
+      value,
+      type: 'number'
+    }
+  }
+  return false
+}
+
+// Returns if a value is an array
+export const isArray = (value: any): ValidationResult => {
+  if (value && typeof value === 'object' && value.constructor === Array) {
+    return {
+      value,
+      type: 'array'
+    }
+  }
+  return false
+}
+
+// Returns if a value is an object
+export const isObject = (value: any): ValidationResult => {
+  if (value && typeof value === 'object' && value.constructor === Object) {
+    return {
+      value,
+      type: 'object'
+    }
+  }
+  return false
+}
+
+// Returns if a value is null
+export const isNull = (value: any): ValidationResult => {
+  if (value === null) {
+    return {
+      value,
+      type: 'null'
+    }
+  }
+  return false
+}
+
+// Returns if a value is undefined
+export const isUndefined = (value: any): ValidationResult => {
+  if (typeof value === 'undefined') {
+    return {
+      value,
+      type: 'undefined'
+    }
+  }
+  return false
+}
+
+// Returns if a value is a boolean
+export const isBoolean = (value: any): ValidationResult => {
+  if (typeof value === 'boolean') {
+    return {
+      value,
+      type: 'boolean'
+    }
+  }
+  return false
+}
+
+// Returns if value is a date object
+export const isDate = (value: any): ValidationResult => {
+  if (value instanceof Date) {
+    return {
+      value,
+      type: 'date'
+    }
+  }
+  return false
+}
diff --git a/lib/utility.js b/lib/utility.js
new file mode 100644
index 0000000..134ccd7
--- /dev/null
+++ b/lib/utility.js
@@ -0,0 +1,12 @@
+// TODO: Flow coverage
+// from: https://hackernoon.com/functional-javascript-resolving-promises-sequentially-7aac18c4431e
+export const promiseSerial = (funcs) => {
+  return funcs.reduce(
+    (promise, func) => {
+      return promise.then((result) => {
+        return func().then(() => {
+          return Array.prototype.concat.bind(result)
+        })
+      })
+    }, Promise.resolve([]))
+}