diff --git a/package.json b/package.json
index 5e1ee22..546fd40 100644
--- a/package.json
+++ b/package.json
@@ -21,6 +21,7 @@
   "repository": "https://github.com/ericmackrodt/staat",
   "devDependencies": {
     "@types/jest": "^23.3.10",
+    "@types/node": "^10.12.18",
     "coveralls": "^3.0.2",
     "jest": "^23.6.0",
     "lerna": "^3.8.5",
diff --git a/packages/time-travel/src/__tests__/time-travel.test.ts b/packages/time-travel/src/__tests__/time-travel.test.ts
index 9bfac08..8ea562f 100644
--- a/packages/time-travel/src/__tests__/time-travel.test.ts
+++ b/packages/time-travel/src/__tests__/time-travel.test.ts
@@ -1,5 +1,169 @@
-describe('TimeTravel', () => {
-  it('does', () => {
-    expect(true).toBe(true);
+import timeTravel from '../time-travel';
+import { scope } from 'staat';
+import { TimeTravelContainer } from '../time-travel-container';
+
+type State = {
+  argument0: string;
+  argument1: string;
+  argument2: number;
+  scope: {
+    scopeArgument: string;
+  };
+};
+
+const baseState: State = {
+  argument0: 'str',
+  argument1: '',
+  argument2: 0,
+  scope: { scopeArgument: '0' },
+};
+
+function transformer(
+  state: State,
+  argument1: string,
+  argument2: number,
+): State {
+  return { ...state, argument1, argument2 };
+}
+
+function transformerPromised(
+  state: State,
+  argument1: string,
+  argument2: number,
+): Promise<State> {
+  return Promise.resolve({ ...state, argument1, argument2 });
+}
+
+describe('timeTravel', () => {
+  let setPresentStub: jest.Mock<{}>;
+  let undoStub: jest.Mock<{}>;
+  let redoStub: jest.Mock<{}>;
+  beforeEach(() => {
+    setPresentStub = jest.fn(TimeTravelContainer.prototype.setPresent);
+    undoStub = jest.fn(TimeTravelContainer.prototype.undo);
+    redoStub = jest.fn(TimeTravelContainer.prototype.redo);
+    TimeTravelContainer.prototype.setPresent = setPresentStub;
+    TimeTravelContainer.prototype.undo = undoStub;
+    TimeTravelContainer.prototype.redo = redoStub;
+  });
+
+  it('retains transformer functionality', () => {
+    const sut = timeTravel({ transformer });
+    expect(transformer(baseState, 'a', 1)).not.toBe(
+      sut.transformer(baseState, 'a', 1),
+    );
+    expect(sut.transformer(baseState, 'a', 1)).toEqual(
+      transformer(baseState, 'a', 1),
+    );
+  });
+
+  it('retains transformer functionality with promise', async () => {
+    const sut = timeTravel({ transformerPromised });
+    expect(await sut.transformerPromised(baseState, 'a', 1)).not.toBe(
+      await transformerPromised(baseState, 'a', 1),
+    );
+    expect(await sut.transformerPromised(baseState, 'a', 1)).toEqual(
+      await transformerPromised(baseState, 'a', 1),
+    );
+  });
+
+  it('builds object with time travel functions', () => {
+    const sut = timeTravel({ transformer });
+    expect(sut).toHaveProperty('undo');
+    expect(sut).toHaveProperty('redo');
+  });
+
+  it('sets up scoped transformers', () => {
+    const testScope = scope<State, 'scope'>('scope');
+    const scopedTransformer = testScope.transformer(
+      (currentScope, scopeArgument: string) => {
+        return { ...currentScope, scopeArgument };
+      },
+    );
+    const sut = timeTravel({ scopedTransformer }, testScope);
+    expect(sut.scopedTransformer(baseState, 'scoped_value')).not.toBe(
+      scopedTransformer(baseState, 'scoped_value'),
+    );
+    expect(sut.scopedTransformer(baseState, 'scoped_value')).toEqual(
+      scopedTransformer(baseState, 'scoped_value'),
+    );
+  });
+
+  it('calls setPresent when calling transformer', () => {
+    const sut = timeTravel({ transformer });
+    sut.transformer(baseState, 'a', 1);
+    expect(setPresentStub).toHaveBeenCalledTimes(1);
+  });
+
+  it('calls scoped setPresent when calling transformer', () => {
+    const testScope = scope<State, 'scope'>('scope');
+    const scopedTransformer = testScope.transformer(
+      (currentScope, scopeArgument: string) => {
+        return { ...currentScope, scopeArgument };
+      },
+    );
+    const sut = timeTravel({ scopedTransformer }, testScope);
+    sut.scopedTransformer(baseState, 'scoped_value');
+    expect(setPresentStub).toHaveBeenCalledTimes(1);
+    expect(setPresentStub).toHaveBeenCalledWith(
+      { scopeArgument: '0' },
+      { scopeArgument: 'scoped_value' },
+    );
+  });
+
+  it('calls undo', () => {
+    const sut = timeTravel({ transformer });
+    const newState = sut.transformer(baseState, 'new_value', 10) as State;
+    sut.undo(newState);
+    expect(undoStub).toHaveBeenCalledTimes(1);
+    expect(undoStub).toHaveBeenCalledWith({
+      argument0: 'str',
+      argument1: 'new_value',
+      argument2: 10,
+      scope: { scopeArgument: '0' },
+    });
+  });
+
+  it('calls scoped undo', () => {
+    const testScope = scope<State, 'scope'>('scope');
+    const scopedTransformer = testScope.transformer(
+      (currentScope, scopeArgument: string) => {
+        return { ...currentScope, scopeArgument };
+      },
+    );
+    const sut = timeTravel({ scopedTransformer }, testScope);
+    const newState = sut.scopedTransformer(baseState, 'scoped_value') as State;
+    sut.undo(newState);
+    expect(undoStub).toHaveBeenCalledTimes(1);
+    expect(undoStub).toHaveBeenCalledWith({ scopeArgument: 'scoped_value' });
+  });
+
+  it('calls redo', () => {
+    const sut = timeTravel({ transformer });
+    let newState = sut.transformer(baseState, 'new_value', 10) as State;
+    newState = sut.undo(newState) as State;
+    sut.redo(newState);
+    expect(redoStub).toHaveBeenCalledTimes(1);
+    expect(redoStub).toHaveBeenCalledWith({
+      argument0: 'str',
+      argument1: '',
+      argument2: 0,
+      scope: { scopeArgument: '0' },
+    });
+  });
+
+  it('calls scoped redo', () => {
+    const testScope = scope<State, 'scope'>('scope');
+    const scopedTransformer = testScope.transformer(
+      (currentScope, scopeArgument: string) => {
+        return { ...currentScope, scopeArgument };
+      },
+    );
+    const sut = timeTravel({ scopedTransformer }, testScope);
+    let newState = sut.scopedTransformer(baseState, 'scoped_value') as State;
+    newState = sut.undo(newState) as State;
+    sut.redo(newState);
+    expect(redoStub).toHaveBeenCalledTimes(1);
+    expect(redoStub).toHaveBeenCalledWith({ scopeArgument: '0' });
   });
 });
diff --git a/packages/time-travel/src/__tests__/utils.test.ts b/packages/time-travel/src/__tests__/utils.test.ts
new file mode 100644
index 0000000..7f010ac
--- /dev/null
+++ b/packages/time-travel/src/__tests__/utils.test.ts
@@ -0,0 +1,18 @@
+import * as utils from '../utils';
+
+describe('timeTravel/utils', () => {
+  test('getKeys', () => {
+    expect(utils.getKeys({ prop1: '', prop2: 0 })).toEqual(['prop1', 'prop2']);
+    expect(utils.getKeys({ keyA: new Date(), keyB: ['array'] })).toEqual([
+      'keyA',
+      'keyB',
+    ]);
+  });
+
+  test('asArray', () => {
+    expect(utils.asArray('test')).toEqual(['test']);
+    expect(utils.asArray(['test'])).toEqual(['test']);
+    expect(utils.asArray(1)).toEqual([1]);
+    expect(utils.asArray([1])).toEqual([1]);
+  });
+});
diff --git a/yarn.lock b/yarn.lock
index 7128596..80d3659 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -605,6 +605,11 @@
   version "23.3.10"
   resolved "https://registry.yarnpkg.com/@types/jest/-/jest-23.3.10.tgz#4897974cc317bf99d4fe6af1efa15957fa9c94de"
 
+"@types/node@^10.12.18":
+  version "10.12.18"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-10.12.18.tgz#1d3ca764718915584fcd9f6344621b7672665c67"
+  integrity sha512-fh+pAqt4xRzPfqA6eh3Z2y6fyZavRIumvjhaCL753+TVkGKGhpPeyrJG2JftD0T9q4GF00KjefsQ+PQNDdWQaQ==
+
 "@types/prop-types@*":
   version "15.5.8"
   resolved "https://registry.yarnpkg.com/@types/prop-types/-/prop-types-15.5.8.tgz#8ae4e0ea205fe95c3901a5a1df7f66495e3a56ce"