diff --git a/SPIKE.md b/SPIKE.md
new file mode 100644
index 000000000000..4e442e25db75
--- /dev/null
+++ b/SPIKE.md
@@ -0,0 +1,141 @@
+# Run LB3 tests from LB4 when LB3 is mounted on the LB4 app
+
+Since LoopBack 4 offers a way to mount LoopBack 3 applications on a LoopBack 4
+project with the use of
+[`@loopback/booter-lb3app`](https://github.com/strongloop/loopback-next/tree/master/packages/booter-lb3app),
+there should also be a way for users to run their LoopBack 3 tests as part of
+LoopBack 4's `npm test` command.
+
+We want the LoopBack 3 tests to use the LoopBack 4 server rather than the
+LoopBack 3 application. This spike aims to test running both acceptance and
+integration LoopBack 3 tests.
+
+## All Tests
+
+In order to run LoopBack 3's tests from their current folder, add LB3 tests'
+path to `test` entry in package.json:
+
+- `"test": "lb-mocha \"dist/**tests**/\*_/_.js\" \"lb3app/test/\*.js\""`
+
+In this case, the test folder is
+[`/lb3app/test`](https://github.com/strongloop/loopback-next/tree/spike/lb3test/examples/lb3-application/lb3app/test)
+from the root of the LoopBack 4 project.
+
+This will run LoopBack 4 tests first then LoopBack 3 tests.
+
+## Acceptance Tests
+
+First, move any LoopBack 3 test dependencies to package.json's devDependencies
+and run:
+
+```sh
+npm install
+```
+
+In your test file:
+
+- Update to use the LB4 Express server when doing requests:
+
+  ```ts
+  // can use lb4's testlab's supertest as the dependency is already installed
+  const {supertest} = require('@loopback/testlab');
+  const assert = require('assert');
+  const should = require('should');
+  const {ExpressServer} = require('../../dist/server');
+
+  let app;
+
+  function request(verb, url) {
+    // use the LB4 express server
+    return supertest(app.server)
+      [verb](url)
+      .set('Content-Type', 'application/json')
+      .set('Accept', 'application/json')
+      .expect('Content-Type', /json/);
+  }
+  ```
+
+- Boot and start the LB4 app in your before hook, and stop the app in the after
+  hook:
+
+  ```ts
+  describe('LoopBack 3 style tests', function () {
+    before(async function () {
+      app = new ExpressServer();
+      await app.boot();
+      await app.start();
+    });
+
+    after(async () => {
+      await app.stop();
+    });
+
+    // your tests here
+  });
+  ```
+
+- Example of this use can be seen in
+  [`examples/lb3-application/lb3app/test/acceptance.js`](https://github.com/strongloop/loopback-next/blob/spike/lb3test/examples/lb3-application/lb3app/test/acceptance.js)
+  which has the same tests as
+  [`src/__tests__/acceptance/lb3app.acceptance.ts`](https://github.com/strongloop/loopback-next/blob/spike/lb3test/examples/lb3-application/src/__tests__/acceptance/lb3app.acceptance.ts),
+  but in LB3 style.
+
+Now when you run `npm test` your LoopBack 3 tests should be run along with any
+LoopBack 4 tests you have.
+
+Optional: Another option is to migrate your tests to use LoopBack 4 style of
+testing, similar to `src/__tests__/acceptance/lb3app.acceptance.ts`.
+Documentation for LoopBack testing can be found in
+https://loopback.io/doc/en/lb4/Testing-your-application.html.
+
+## Integration Tests
+
+For the integration tests, LoopBack 3 models were bound to the LoopBack 4
+application in order to allow JavaScript API to call application logic such as
+`Model.create()`. This can be seen in
+[`packages/booter-lb3app/src/lb3app.booter.ts`](https://github.com/strongloop/loopback-next/blob/spike/lb3test/packages/booter-lb3app/src/lb3app.booter.ts#L76-L85).
+
+In order to retrieve the model from the application's context, `getSync()` can
+be used as follows:
+
+```ts
+describe('LoopBack 3 style integration tests', function () {
+  let app;
+  let CoffeeShop;
+
+  before(async function () {
+    app = new ExpressServer();
+    await app.boot();
+    await app.start();
+  });
+
+  before(() => {
+    // follow the syntax: lb3-models.{ModelName}
+    CoffeeShop = app.lbApp.getSync('lb3-models.CoffeeShop');
+  });
+
+  after(async () => {
+    await app.stop();
+  });
+
+  // your tests here
+});
+```
+
+Alternatively, `get()` can also be used in to retrieve the model asynchronously:
+
+```ts
+before(async () => {
+  // follow the syntax: lb3-models.{ModelName}
+  CoffeeShop = await app.lbApp.get('lb3-models.CoffeeShop');
+});
+```
+
+Additionally, LB3 datasources are also bound to the LB4 application's context
+and can be retrieved with a key in the syntax `lb3-datasources.{ds name}`.
+
+Example integration tests can be found in
+[`examples/lb3-application/lb3app/test/integration.js`](https://github.com/strongloop/loopback-next/blob/spike/lb3test/examples/lb3-application/lb3app/test/integration.js).
+
+Example authentication tests can be found in
+[`examples/lb3-application/lb3app/test/authentication.js`](https://github.com/strongloop/loopback-next/blob/spike/lb3test/examples/lb3-application/lb3app/test/authentication.js).
diff --git a/examples/lb3-application/lb3app/common/models/coffee-shop.js b/examples/lb3-application/lb3app/common/models/coffee-shop.js
index 4917a2f582ef..c88f44497b2c 100755
--- a/examples/lb3-application/lb3app/common/models/coffee-shop.js
+++ b/examples/lb3-application/lb3app/common/models/coffee-shop.js
@@ -38,6 +38,6 @@ module.exports = function (CoffeeShop) {
   };
   CoffeeShop.remoteMethod('greet', {
     http: {path: '/greet', verb: 'get'},
-    returns: {type: 'string'},
+    returns: {arg: 'greeting', type: 'string'},
   });
 };
diff --git a/examples/lb3-application/lb3app/test/acceptance.js b/examples/lb3-application/lb3app/test/acceptance.js
new file mode 100644
index 000000000000..e9ad4e5ac874
--- /dev/null
+++ b/examples/lb3-application/lb3app/test/acceptance.js
@@ -0,0 +1,72 @@
+// Copyright IBM Corp. 2020. All Rights Reserved.
+// Node module: @loopback/example-lb3-application
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+const {supertest} = require('@loopback/testlab');
+const assert = require('assert');
+const {ExpressServer} = require('../../dist/server');
+require('should');
+
+let app;
+
+function request(verb, url) {
+  // use the original app's server
+  return supertest(app.server)
+    [verb](url)
+    .set('Content-Type', 'application/json')
+    .set('Accept', 'application/json')
+    .expect('Content-Type', /json/);
+}
+
+describe('LoopBack 3 style acceptance tests', function () {
+  before(async function () {
+    app = new ExpressServer();
+    await app.boot();
+    await app.start();
+  });
+
+  after(async () => {
+    await app.stop();
+  });
+
+  context('basic REST calls for LoopBack 3 application', () => {
+    it('creates and finds a CoffeeShop', function (done) {
+      request('post', '/api/CoffeeShops')
+        .send({
+          name: 'Coffee Shop',
+          city: 'Toronto',
+        })
+        .expect(200)
+        .end(function (err, res) {
+          assert(typeof res.body === 'object');
+          assert(res.body.name);
+          assert(res.body.city);
+          assert.equal(res.body.name, 'Coffee Shop');
+          assert.equal(res.body.city, 'Toronto');
+          done();
+        });
+    });
+
+    it("gets the CoffeeShop's status", function (done) {
+      request('get', '/api/CoffeeShops/status').expect(200, function (
+        err,
+        res,
+      ) {
+        res.body.status.should.be.equalOneOf(
+          'We are open for business.',
+          'Sorry, we are closed. Open daily from 6am to 8pm.',
+        );
+        done();
+      });
+    });
+
+    it('gets external route in application', function (done) {
+      request('get', '/ping').expect(200, function (err, res) {
+        assert.equal(res.text, 'pong');
+        done();
+      });
+    });
+  });
+});
diff --git a/examples/lb3-application/lb3app/test/authentication.js b/examples/lb3-application/lb3app/test/authentication.js
new file mode 100644
index 000000000000..71f8423d8d22
--- /dev/null
+++ b/examples/lb3-application/lb3app/test/authentication.js
@@ -0,0 +1,99 @@
+// Copyright IBM Corp. 2020. All Rights Reserved.
+// Node module: @loopback/example-lb3-application
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+const lb3App = require('../server/server');
+const {supertest} = require('@loopback/testlab');
+const assert = require('assert');
+const {ExpressServer} = require('../../dist/server');
+require('should');
+
+let app;
+
+function request(verb, url) {
+  // use the original app's server
+  return supertest(app.server)
+    [verb](url)
+    .set('Content-Type', 'application/json')
+    .set('Accept', 'application/json')
+    .expect('Content-Type', /json/);
+}
+
+describe('LoopBack 3 authentication', function () {
+  before(async function () {
+    app = new ExpressServer();
+    await app.boot();
+    await app.start();
+  });
+
+  after(async () => {
+    await app.stop();
+  });
+
+  context('authentication', () => {
+    let User;
+
+    before(() => {
+      User = lb3App.models.User;
+    });
+
+    it('creates a User and logs them in and out', function (done) {
+      request('post', '/api/users')
+        .send({email: 'new@email.com', password: 'L00pBack!'})
+        .expect(200, function (err, user) {
+          assert.equal(user.body.email, 'new@email.com');
+          request('post', '/api/users/login')
+            .send({
+              email: 'new@email.com',
+              password: 'L00pBack!',
+            })
+            .expect(200, function (err2, token) {
+              token.body.should.have.properties(
+                'ttl',
+                'userId',
+                'created',
+                'id',
+              );
+              assert.equal(token.body.userId, user.body.id);
+              request(
+                'post',
+                `/api/users/logout?access_token=${token.body.id}`,
+              ).expect(204);
+              done();
+            });
+        });
+    });
+
+    it('rejects anonymous requests to protected endpoints', function (done) {
+      request('get', '/api/CoffeeShops/greet').expect(401, function (err, res) {
+        assert.equal(res.body.error.code, 'AUTHORIZATION_REQUIRED');
+      });
+      done();
+    });
+
+    it('makes an authenticated request', function (done) {
+      User.create({email: 'new@gmail.com', password: 'L00pBack!'}, function (
+        err,
+        user,
+      ) {
+        user.email.should.be.equal('new@gmail.com');
+        User.login({email: 'new@gmail.com', password: 'L00pBack!'}, function (
+          err2,
+          token,
+        ) {
+          assert.equal(typeof token, 'object');
+          assert.equal(token.userId, user.id);
+          request(
+            'get',
+            `/api/CoffeeShops/greet?access_token=${token.id}`,
+          ).expect(200, function (err3, res) {
+            res.body.greeting.should.be.equal('Hello from this Coffee Shop');
+            done();
+          });
+        });
+      });
+    });
+  });
+});
diff --git a/examples/lb3-application/lb3app/test/integration.js b/examples/lb3-application/lb3app/test/integration.js
new file mode 100644
index 000000000000..4160eeca799e
--- /dev/null
+++ b/examples/lb3-application/lb3app/test/integration.js
@@ -0,0 +1,58 @@
+// Copyright IBM Corp. 2020. All Rights Reserved.
+// Node module: @loopback/example-lb3-application
+// This file is licensed under the MIT License.
+// License text available at https://opensource.org/licenses/MIT
+
+'use strict';
+
+const assert = require('assert');
+const ExpressServer = require('../../dist/server').ExpressServer;
+require('should');
+
+describe('LoopBack 3 style integration tests', function () {
+  let app;
+  let CoffeeShop;
+
+  before(async function () {
+    app = new ExpressServer();
+    await app.boot();
+    await app.start();
+  });
+
+  before(() => {
+    CoffeeShop = app.lbApp.getSync('lb3-models.CoffeeShop');
+  });
+
+  after(async () => {
+    await app.stop();
+  });
+
+  it('CoffeeShop.find', function (done) {
+    CoffeeShop.find({where: {name: 'Bel Cafe'}}, function (err, shop) {
+      shop[0].__data.name.should.be.equal('Bel Cafe');
+      shop[0].__data.city.should.be.equal('Vancouver');
+    });
+    done();
+  });
+
+  it('CoffeeShop.count', function (done) {
+    CoffeeShop.count({}, function (err, count) {
+      assert.equal(count, 5);
+    });
+    done();
+  });
+
+  it('CoffeeShop.create', function (done) {
+    CoffeeShop.create(
+      {
+        name: 'Nook Shop',
+        city: 'Toronto',
+      },
+      function (err, shop) {
+        shop.__data.name.should.be.equal('Nook Shop');
+        shop.__data.city.should.be.equal('Toronto');
+      },
+    );
+    done();
+  });
+});
diff --git a/examples/lb3-application/package-lock.json b/examples/lb3-application/package-lock.json
index 265f7c003427..0dd8cad4f73b 100644
--- a/examples/lb3-application/package-lock.json
+++ b/examples/lb3-application/package-lock.json
@@ -2640,6 +2640,60 @@
 				"nanoid": "^2.1.0"
 			}
 		},
+		"should": {
+			"version": "13.2.3",
+			"resolved": "https://registry.npmjs.org/should/-/should-13.2.3.tgz",
+			"integrity": "sha512-ggLesLtu2xp+ZxI+ysJTmNjh2U0TsC+rQ/pfED9bUZZ4DKefP27D+7YJVVTvKsmjLpIi9jAa7itwDGkDDmt1GQ==",
+			"dev": true,
+			"requires": {
+				"should-equal": "^2.0.0",
+				"should-format": "^3.0.3",
+				"should-type": "^1.4.0",
+				"should-type-adaptors": "^1.0.1",
+				"should-util": "^1.0.0"
+			}
+		},
+		"should-equal": {
+			"version": "2.0.0",
+			"resolved": "https://registry.npmjs.org/should-equal/-/should-equal-2.0.0.tgz",
+			"integrity": "sha512-ZP36TMrK9euEuWQYBig9W55WPC7uo37qzAEmbjHz4gfyuXrEUgF8cUvQVO+w+d3OMfPvSRQJ22lSm8MQJ43LTA==",
+			"dev": true,
+			"requires": {
+				"should-type": "^1.4.0"
+			}
+		},
+		"should-format": {
+			"version": "3.0.3",
+			"resolved": "https://registry.npmjs.org/should-format/-/should-format-3.0.3.tgz",
+			"integrity": "sha1-m/yPdPo5IFxT04w01xcwPidxJPE=",
+			"dev": true,
+			"requires": {
+				"should-type": "^1.3.0",
+				"should-type-adaptors": "^1.0.1"
+			}
+		},
+		"should-type": {
+			"version": "1.4.0",
+			"resolved": "https://registry.npmjs.org/should-type/-/should-type-1.4.0.tgz",
+			"integrity": "sha1-B1bYzoRt/QmEOmlHcZ36DUz/XPM=",
+			"dev": true
+		},
+		"should-type-adaptors": {
+			"version": "1.1.0",
+			"resolved": "https://registry.npmjs.org/should-type-adaptors/-/should-type-adaptors-1.1.0.tgz",
+			"integrity": "sha512-JA4hdoLnN+kebEp2Vs8eBe9g7uy0zbRo+RMcU0EsNy+R+k049Ki+N5tT5Jagst2g7EAja+euFuoXFCa8vIklfA==",
+			"dev": true,
+			"requires": {
+				"should-type": "^1.3.0",
+				"should-util": "^1.0.0"
+			}
+		},
+		"should-util": {
+			"version": "1.0.1",
+			"resolved": "https://registry.npmjs.org/should-util/-/should-util-1.0.1.tgz",
+			"integrity": "sha512-oXF8tfxx5cDk8r2kYqlkUJzZpDBqVY/II2WhvU0n9Y3XYvAYRmeaf1PvvIvTgPnv4KJ+ES5M0PyDq5Jp+Ygy2g==",
+			"dev": true
+		},
 		"signal-exit": {
 			"version": "3.0.3",
 			"resolved": "https://registry.npmjs.org/signal-exit/-/signal-exit-3.0.3.tgz",
diff --git a/examples/lb3-application/package.json b/examples/lb3-application/package.json
index 5fa158025b99..9441b9286113 100644
--- a/examples/lb3-application/package.json
+++ b/examples/lb3-application/package.json
@@ -19,7 +19,7 @@
     "eslint": "lb-eslint --report-unused-disable-directives .",
     "eslint:fix": "npm run eslint -- --fix",
     "pretest": "npm run build",
-    "test": "lb-mocha \"dist/__tests__/**/*.js\"",
+    "test": "lb-mocha \"dist/__tests__/**/*.js\" \"lb3app/test/*.js\"",
     "test:dev": "lb-mocha --allow-console-logs dist/__tests__/**/*.js && npm run posttest",
     "verify": "npm pack && tar xf loopback-lb3-application*.tgz && tree package && npm run clean",
     "migrate": "node ./dist/migrate",
@@ -67,6 +67,7 @@
     "eslint-plugin-eslint-plugin": "^2.2.1",
     "eslint-plugin-mocha": "^6.3.0",
     "lodash": "^4.17.15",
+    "should": "^13.2.3",
     "typescript": "~3.8.3"
   },
   "keywords": [
diff --git a/examples/lb3-application/src/__tests__/acceptance/lb3app.acceptance.ts b/examples/lb3-application/src/__tests__/acceptance/lb3app.acceptance.ts
index 2c1db8b8e1de..aa2313d1ecc2 100644
--- a/examples/lb3-application/src/__tests__/acceptance/lb3app.acceptance.ts
+++ b/examples/lb3-application/src/__tests__/acceptance/lb3app.acceptance.ts
@@ -90,7 +90,7 @@ describe('CoffeeShopApplication', () => {
         .get(`/api/CoffeeShops/greet?access_token=${token.id}`)
         .expect(200);
 
-      expect(response.body.undefined).to.eql('Hello from this Coffee Shop');
+      expect(response.body.greeting).to.eql('Hello from this Coffee Shop');
     });
 
     it('rejects anonymous requests to protected endpoints', async () => {
diff --git a/examples/lb3-application/src/server.ts b/examples/lb3-application/src/server.ts
index 5f9886cb4266..8f4b0f1f7f8a 100644
--- a/examples/lb3-application/src/server.ts
+++ b/examples/lb3-application/src/server.ts
@@ -19,7 +19,7 @@ const helmet = require('helmet');
 export class ExpressServer {
   private app: express.Application;
   public readonly lbApp: CoffeeShopApplication;
-  private server?: http.Server;
+  public server?: http.Server;
   public url: String;
 
   constructor(options: ApplicationConfig = {}) {
diff --git a/packages/booter-lb3app/src/__tests__/acceptance/booter-lb3app.acceptance.ts b/packages/booter-lb3app/src/__tests__/acceptance/booter-lb3app.acceptance.ts
index 557b42d43af4..402418af143d 100644
--- a/packages/booter-lb3app/src/__tests__/acceptance/booter-lb3app.acceptance.ts
+++ b/packages/booter-lb3app/src/__tests__/acceptance/booter-lb3app.acceptance.ts
@@ -242,4 +242,20 @@ describe('booter-lb3app', () => {
       expect(ds).to.eql(expected);
     });
   });
+
+  context('binding LoopBack 3 models', () => {
+    before(async () => {
+      ({app, client} = await setupApplication({
+        lb3app: {path: '../fixtures/app-with-model'},
+      }));
+    });
+
+    it('binds model to the context', async () => {
+      const expected = require('../../../fixtures/app-with-model').models.Color;
+      const modelBindings = app.findByTag('lb3-model');
+      const key = modelBindings[0].key;
+      const model = await app.get(key);
+      expect(model).to.eql(expected);
+    });
+  });
 });
diff --git a/packages/booter-lb3app/src/lb3app.booter.ts b/packages/booter-lb3app/src/lb3app.booter.ts
index 88050609e5dc..60b5ea5d8bf1 100644
--- a/packages/booter-lb3app/src/lb3app.booter.ts
+++ b/packages/booter-lb3app/src/lb3app.booter.ts
@@ -73,6 +73,17 @@ export class Lb3AppBooter implements Booter {
       });
     }
 
+    const models = lb3App.models;
+    if (models) {
+      const visited: unknown[] = [];
+      Object.keys(models).forEach(key => {
+        const model = models[key];
+        if (visited.includes(model)) return;
+        visited.push(model);
+        this.app.bind(`lb3-models.${key}`).to(model).tag('lb3-model');
+      });
+    }
+
     // TODO(bajtos) Listen for the following events to update the OpenAPI spec:
     // - modelRemoted
     // - modelDeleted
@@ -149,4 +160,6 @@ export interface Lb3AppBooterOptions {
 interface Lb3Application extends ExpressApplication {
   handler(name: 'rest'): ExpressRequestHandler;
   dataSources?: {[name: string]: unknown};
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  models?: {[name: string]: any};
 }