diff --git a/__tests__/getCertain.test.js b/__tests__/getCertain.test.js
index 496b486..d82bf11 100644
--- a/__tests__/getCertain.test.js
+++ b/__tests__/getCertain.test.js
@@ -1,15 +1,18 @@
-// flow
+// @flow
 import getCertain from '../src';
 
 describe('getCertain', () => {
   describe('invariants', () => {
     it('throws if "map" is undefined.', () => {
+      // $FlowFixMe
       expect(() => getCertain()).toThrow('"map" must be a Map.');
     });
     it('throws if "map" is not a Map-like object.', () => {
+      // $FlowFixMe
       expect(() => getCertain({has: 3})).toThrow('"map" must be a Map.');
     });
     it('throws if "message" is not a string or undefined.', () => {
+      // $FlowFixMe
       expect(() => getCertain(new Map(), 1, 1)).toThrow(
         '"message" must be a string or undefined.',
       );
diff --git a/flow-typed/npm/jest_v22.x.x.js b/flow-typed/npm/jest_v23.x.x.js
similarity index 65%
rename from flow-typed/npm/jest_v22.x.x.js
rename to flow-typed/npm/jest_v23.x.x.js
index d91f48e..653840a 100644
--- a/flow-typed/npm/jest_v22.x.x.js
+++ b/flow-typed/npm/jest_v23.x.x.js
@@ -1,5 +1,5 @@
-// flow-typed signature: 17c6ca97e1e560b9bc0d3400f8b2882f
-// flow-typed version: a5bbe16c29/jest_v22.x.x/flow_>=v0.39.x
+// flow-typed signature: bc9e644ba43fa1c4d1fccc5fd47f65e9
+// flow-typed version: d37e775f89/jest_v23.x.x/flow_>=v0.39.x
 
 type JestMockFn<TArguments: $ReadOnlyArray<*>, TReturn> = {
   (...args: TArguments): TReturn,
@@ -156,8 +156,335 @@ type DomTestingLibraryType = {
   toHaveAttribute(name: string, expectedValue?: string): void
 };
 
-type JestExpectType = {
-  not: JestExpectType & EnzymeMatchersType & DomTestingLibraryType,
+// Jest JQuery Matchers: https://github.com/unindented/custom-jquery-matchers
+type JestJQueryMatchersType = {
+  toExist(): void,
+  toHaveLength(len: number): void,
+  toHaveId(id: string): void,
+  toHaveClass(className: string): void,
+  toHaveTag(tag: string): void,
+  toHaveAttr(key: string, val?: any): void,
+  toHaveProp(key: string, val?: any): void,
+  toHaveText(text: string | RegExp): void,
+  toHaveData(key: string, val?: any): void,
+  toHaveValue(val: any): void,
+  toHaveCss(css: {[key: string]: any}): void,
+  toBeChecked(): void,
+  toBeDisabled(): void,
+  toBeEmpty(): void,
+  toBeHidden(): void,
+  toBeSelected(): void,
+  toBeVisible(): void,
+  toBeFocused(): void,
+  toBeInDom(): void,
+  toBeMatchedBy(sel: string): void,
+  toHaveDescendant(sel: string): void,
+  toHaveDescendantWithText(sel: string, text: string | RegExp): void
+};
+
+
+// Jest Extended Matchers: https://github.com/jest-community/jest-extended
+type JestExtendedMatchersType = {
+  /**
+     * Note: Currently unimplemented
+     * Passing assertion
+     *
+     * @param {String} message
+     */
+  //  pass(message: string): void;
+
+    /**
+     * Note: Currently unimplemented
+     * Failing assertion
+     *
+     * @param {String} message
+     */
+  //  fail(message: string): void;
+
+    /**
+     * Use .toBeEmpty when checking if a String '', Array [] or Object {} is empty.
+     */
+    toBeEmpty(): void;
+
+    /**
+     * Use .toBeOneOf when checking if a value is a member of a given Array.
+     * @param {Array.<*>} members
+     */
+    toBeOneOf(members: any[]): void;
+
+    /**
+     * Use `.toBeNil` when checking a value is `null` or `undefined`.
+     */
+    toBeNil(): void;
+
+    /**
+     * Use `.toSatisfy` when you want to use a custom matcher by supplying a predicate function that returns a `Boolean`.
+     * @param {Function} predicate
+     */
+    toSatisfy(predicate: (n: any) => boolean): void;
+
+    /**
+     * Use `.toBeArray` when checking if a value is an `Array`.
+     */
+    toBeArray(): void;
+
+    /**
+     * Use `.toBeArrayOfSize` when checking if a value is an `Array` of size x.
+     * @param {Number} x
+     */
+    toBeArrayOfSize(x: number): void;
+
+    /**
+     * Use `.toIncludeAllMembers` when checking if an `Array` contains all of the same members of a given set.
+     * @param {Array.<*>} members
+     */
+    toIncludeAllMembers(members: any[]): void;
+
+    /**
+     * Use `.toIncludeAnyMembers` when checking if an `Array` contains any of the members of a given set.
+     * @param {Array.<*>} members
+     */
+    toIncludeAnyMembers(members: any[]): void;
+
+    /**
+     * Use `.toSatisfyAll` when you want to use a custom matcher by supplying a predicate function that returns a `Boolean` for all values in an array.
+     * @param {Function} predicate
+     */
+    toSatisfyAll(predicate: (n: any) => boolean): void;
+
+    /**
+     * Use `.toBeBoolean` when checking if a value is a `Boolean`.
+     */
+    toBeBoolean(): void;
+
+    /**
+     * Use `.toBeTrue` when checking a value is equal (===) to `true`.
+     */
+    toBeTrue(): void;
+
+    /**
+     * Use `.toBeFalse` when checking a value is equal (===) to `false`.
+     */
+    toBeFalse(): void;
+
+    /**
+     * Use .toBeDate when checking if a value is a Date.
+     */
+    toBeDate(): void;
+
+    /**
+     * Use `.toBeFunction` when checking if a value is a `Function`.
+     */
+    toBeFunction(): void;
+
+    /**
+     * Use `.toHaveBeenCalledBefore` when checking if a `Mock` was called before another `Mock`.
+     *
+     * Note: Required Jest version >22
+     * Note: Your mock functions will have to be asynchronous to cause the timestamps inside of Jest to occur in a differentJS event loop, otherwise the mock timestamps will all be the same
+     *
+     * @param {Mock} mock
+     */
+    toHaveBeenCalledBefore(mock: JestMockFn<any, any>): void;
+
+    /**
+     * Use `.toBeNumber` when checking if a value is a `Number`.
+     */
+    toBeNumber(): void;
+
+    /**
+     * Use `.toBeNaN` when checking a value is `NaN`.
+     */
+    toBeNaN(): void;
+
+    /**
+     * Use `.toBeFinite` when checking if a value is a `Number`, not `NaN` or `Infinity`.
+     */
+    toBeFinite(): void;
+
+    /**
+     * Use `.toBePositive` when checking if a value is a positive `Number`.
+     */
+    toBePositive(): void;
+
+    /**
+     * Use `.toBeNegative` when checking if a value is a negative `Number`.
+     */
+    toBeNegative(): void;
+
+    /**
+     * Use `.toBeEven` when checking if a value is an even `Number`.
+     */
+    toBeEven(): void;
+
+    /**
+     * Use `.toBeOdd` when checking if a value is an odd `Number`.
+     */
+    toBeOdd(): void;
+
+    /**
+     * Use `.toBeWithin` when checking if a number is in between the given bounds of: start (inclusive) and end (exclusive).
+     *
+     * @param {Number} start
+     * @param {Number} end
+     */
+    toBeWithin(start: number, end: number): void;
+
+    /**
+     * Use `.toBeObject` when checking if a value is an `Object`.
+     */
+    toBeObject(): void;
+
+    /**
+     * Use `.toContainKey` when checking if an object contains the provided key.
+     *
+     * @param {String} key
+     */
+    toContainKey(key: string): void;
+
+    /**
+     * Use `.toContainKeys` when checking if an object has all of the provided keys.
+     *
+     * @param {Array.<String>} keys
+     */
+    toContainKeys(keys: string[]): void;
+
+    /**
+     * Use `.toContainAllKeys` when checking if an object only contains all of the provided keys.
+     *
+     * @param {Array.<String>} keys
+     */
+    toContainAllKeys(keys: string[]): void;
+
+    /**
+     * Use `.toContainAnyKeys` when checking if an object contains at least one of the provided keys.
+     *
+     * @param {Array.<String>} keys
+     */
+    toContainAnyKeys(keys: string[]): void;
+
+    /**
+     * Use `.toContainValue` when checking if an object contains the provided value.
+     *
+     * @param {*} value
+     */
+    toContainValue(value: any): void;
+
+    /**
+     * Use `.toContainValues` when checking if an object contains all of the provided values.
+     *
+     * @param {Array.<*>} values
+     */
+    toContainValues(values: any[]): void;
+
+    /**
+     * Use `.toContainAllValues` when checking if an object only contains all of the provided values.
+     *
+     * @param {Array.<*>} values
+     */
+    toContainAllValues(values: any[]): void;
+
+    /**
+     * Use `.toContainAnyValues` when checking if an object contains at least one of the provided values.
+     *
+     * @param {Array.<*>} values
+     */
+    toContainAnyValues(values: any[]): void;
+
+    /**
+     * Use `.toContainEntry` when checking if an object contains the provided entry.
+     *
+     * @param {Array.<String, String>} entry
+     */
+    toContainEntry(entry: [string, string]): void;
+
+    /**
+     * Use `.toContainEntries` when checking if an object contains all of the provided entries.
+     *
+     * @param {Array.<Array.<String, String>>} entries
+     */
+    toContainEntries(entries: [string, string][]): void;
+
+    /**
+     * Use `.toContainAllEntries` when checking if an object only contains all of the provided entries.
+     *
+     * @param {Array.<Array.<String, String>>} entries
+     */
+    toContainAllEntries(entries: [string, string][]): void;
+
+    /**
+     * Use `.toContainAnyEntries` when checking if an object contains at least one of the provided entries.
+     *
+     * @param {Array.<Array.<String, String>>} entries
+     */
+    toContainAnyEntries(entries: [string, string][]): void;
+
+    /**
+     * Use `.toBeExtensible` when checking if an object is extensible.
+     */
+    toBeExtensible(): void;
+
+    /**
+     * Use `.toBeFrozen` when checking if an object is frozen.
+     */
+    toBeFrozen(): void;
+
+    /**
+     * Use `.toBeSealed` when checking if an object is sealed.
+     */
+    toBeSealed(): void;
+
+    /**
+     * Use `.toBeString` when checking if a value is a `String`.
+     */
+    toBeString(): void;
+
+    /**
+     * Use `.toEqualCaseInsensitive` when checking if a string is equal (===) to another ignoring the casing of both strings.
+     *
+     * @param {String} string
+     */
+    toEqualCaseInsensitive(string: string): void;
+
+    /**
+     * Use `.toStartWith` when checking if a `String` starts with a given `String` prefix.
+     *
+     * @param {String} prefix
+     */
+    toStartWith(prefix: string): void;
+
+    /**
+     * Use `.toEndWith` when checking if a `String` ends with a given `String` suffix.
+     *
+     * @param {String} suffix
+     */
+    toEndWith(suffix: string): void;
+
+    /**
+     * Use `.toInclude` when checking if a `String` includes the given `String` substring.
+     *
+     * @param {String} substring
+     */
+    toInclude(substring: string): void;
+
+    /**
+     * Use `.toIncludeRepeated` when checking if a `String` includes the given `String` substring the correct number of times.
+     *
+     * @param {String} substring
+     * @param {Number} times
+     */
+    toIncludeRepeated(substring: string, times: number): void;
+
+    /**
+     * Use `.toIncludeMultiple` when checking if a `String` includes all of the given substrings.
+     *
+     * @param {Array.<String>} substring
+     */
+    toIncludeMultiple(substring: string[]): void;
+};
+
+interface JestExpectType {
+  not: JestExpectType & EnzymeMatchersType & DomTestingLibraryType & JestJQueryMatchersType & JestExtendedMatchersType,
   /**
    * If you have a mock function, you can use .lastCalledWith to test what
    * arguments it was last called with.
@@ -168,10 +495,6 @@ type JestExpectType = {
    * strict equality.
    */
   toBe(value: any): void,
-  /**
-   * Use .toHaveBeenCalled to ensure that a mock function got called.
-   */
-  toBeCalled(): void,
   /**
    * Use .toBeCalledWith to ensure that a mock function was called with
    * specific arguments.
@@ -247,21 +570,55 @@ type JestExpectType = {
    * Use .toHaveBeenCalled to ensure that a mock function got called.
    */
   toHaveBeenCalled(): void,
+  toBeCalled(): void;
   /**
    * Use .toHaveBeenCalledTimes to ensure that a mock function got called exact
    * number of times.
    */
   toHaveBeenCalledTimes(number: number): void,
+  toBeCalledTimes(number: number): void;
+  /**
+   *
+   */
+  toHaveBeenNthCalledWith(nthCall: number, ...args: Array<any>): void;
+  nthCalledWith(nthCall: number, ...args: Array<any>): void;
+  /**
+   *
+   */
+  toHaveReturned(): void;
+  toReturn(): void;
+  /**
+   *
+   */
+  toHaveReturnedTimes(number: number): void;
+  toReturnTimes(number: number): void;
+  /**
+   *
+   */
+  toHaveReturnedWith(value: any): void;
+  toReturnWith(value: any): void;
+  /**
+   *
+   */
+  toHaveLastReturnedWith(value: any): void;
+  lastReturnedWith(value: any): void;
+  /**
+   *
+   */
+  toHaveNthReturnedWith(nthCall: number, value: any): void;
+  nthReturnedWith(nthCall: number, value: any): void;
   /**
    * Use .toHaveBeenCalledWith to ensure that a mock function was called with
    * specific arguments.
    */
   toHaveBeenCalledWith(...args: Array<any>): void,
+  toBeCalledWith(...args: Array<any>): void,
   /**
    * Use .toHaveBeenLastCalledWith to ensure that a mock function was last called
    * with specific arguments.
    */
   toHaveBeenLastCalledWith(...args: Array<any>): void,
+  lastCalledWith(...args: Array<any>): void,
   /**
    * Check that an object has a .length property and it is set to a certain
    * numeric value.
@@ -280,9 +637,13 @@ type JestExpectType = {
    */
   toMatchObject(object: Object | Array<Object>): void,
   /**
-   * This ensures that a React component matches the most recent snapshot.
+   * This ensures that an Object matches the most recent snapshot.
    */
-  toMatchSnapshot(name?: string): void,
+  toMatchSnapshot(propertyMatchers?: {[key: string]: JestAsymmetricEqualityType}, name?: string): void,
+  /**
+   * This ensures that an Object matches the most recent snapshot.
+   */
+  toMatchSnapshot(name: string): void,
   /**
    * Use .toThrow to test that a function throws when it is called.
    * If you want to test that a specific error gets thrown, you can provide an
@@ -298,7 +659,7 @@ type JestExpectType = {
    * matching the most recent snapshot when it is called.
    */
   toThrowErrorMatchingSnapshot(): void
-};
+}
 
 type JestObjectType = {
   /**
@@ -451,7 +812,7 @@ type JestObjectType = {
    * Creates a mock function similar to jest.fn but also tracks calls to
    * object[methodName].
    */
-  spyOn(object: Object, methodName: string): JestMockFn<any, any>,
+  spyOn(object: Object, methodName: string, accessType?: "get" | "set"): JestMockFn<any, any>,
   /**
    * Set the default timeout interval for tests and before/after hooks in milliseconds.
    * Note: The default timeout interval is 5 seconds if this method is not called.
@@ -618,7 +979,7 @@ type JestPrettyFormatPlugins = Array<JestPrettyFormatPlugin>;
 /** The expect function is used every time you want to test a value */
 declare var expect: {
   /** The object that you want to make assertions against */
-  (value: any): JestExpectType & JestPromiseType & EnzymeMatchersType & DomTestingLibraryType,
+  (value: any): JestExpectType & JestPromiseType & EnzymeMatchersType & DomTestingLibraryType & JestJQueryMatchersType & JestExtendedMatchersType,
   /** Add additional Jasmine matchers to Jest's roster */
   extend(matchers: { [name: string]: JestMatcher }): void,
   /** Add a module that formats application-specific data structures. */
diff --git a/package.json b/package.json
index 0ddab57..3d30b81 100644
--- a/package.json
+++ b/package.json
@@ -11,15 +11,15 @@
   },
   "description": "Assert a Map has a given key and return the value for it.",
   "devDependencies": {
-    "@babel/core": "^7.0.0-beta.44",
-    "@babel/preset-env": "^7.0.0-beta.44",
-    "@babel/preset-flow": "^7.0.0-beta.44",
+    "@babel/core": "^7.0.0-beta.46",
+    "@babel/preset-env": "^7.0.0-beta.46",
+    "@babel/preset-flow": "^7.0.0-beta.46",
     "@commitlint/cli": "^7.0.0",
     "@commitlint/config-conventional": "^7.0.0",
+    "@wtg/scripts": "^1.1.2",
     "babel-core": "7.0.0-bridge.0",
     "babel-eslint": "^8.2.3",
     "babel-jest": "^23.0.0",
-    "builtin-modules": "^2.0.0",
     "eslint": "^4.19.1",
     "eslint-config-airbnb-base": "^12.1.0",
     "eslint-config-prettier": "^2.9.0",
@@ -30,10 +30,7 @@
     "jest": "^23.0.0",
     "lint-staged": "^7.0.4",
     "prettier": "1.13.5",
-    "rimraf": "^2.6.2",
-    "rollup": "^0.58.1",
-    "rollup-plugin-babel": "^4.0.0-beta.4",
-    "write": "^1.0.3"
+    "rimraf": "^2.6.2"
   },
   "engines": {
     "node": ">=6"
@@ -51,7 +48,7 @@
     "url": "https://github.com/wtgtybhertgeghgtwtg/get-certain"
   },
   "scripts": {
-    "build": "node scripts/build",
+    "build": "wtg build",
     "clean": "rimraf coverage dist",
     "lint": "flow && eslint . && prettier --l \"{__tests__,src}/**/*.js\"",
     "test": "yarn test:src && yarn build && yarn test:dist",
diff --git a/renovate.json b/renovate.json
index 2047292..18dddee 100644
--- a/renovate.json
+++ b/renovate.json
@@ -1,4 +1,7 @@
 {
   "extends": ["config:base", "docker:disable"],
+  "devDependencies": {
+    "automerge": true
+  },
   "pinVersions": false
 }
diff --git a/scripts/build.js b/scripts/build.js
deleted file mode 100644
index 24b49e2..0000000
--- a/scripts/build.js
+++ /dev/null
@@ -1,15 +0,0 @@
-const builtinModules = require('builtin-modules');
-const {rollup} = require('rollup');
-const babel = require('rollup-plugin-babel');
-const write = require('write');
-const pkg = require('../package.json');
-
-rollup({
-  external: [...builtinModules, ...Object.keys(pkg.dependencies)],
-  input: 'src/index.js',
-  plugins: [babel()],
-}).then(async bundle => {
-  await bundle.write({file: pkg.main, format: 'cjs', sourcemap: true});
-  await write(`${pkg.main}.flow`, "// @flow\nexport * from '../src';");
-  await bundle.write({file: pkg.module, format: 'es', sourcemap: true});
-});