diff --git a/test/backchannel_logout/backchannel_logout.test.js b/test/backchannel_logout/backchannel_logout.test.js
index a1406f648..c775809fa 100644
--- a/test/backchannel_logout/backchannel_logout.test.js
+++ b/test/backchannel_logout/backchannel_logout.test.js
@@ -1,3 +1,4 @@
+const { strict: assert } = require('assert');
 const { parse: parseUrl } = require('url');
 
 const sinon = require('sinon').createSandbox();
@@ -7,8 +8,6 @@ const nock = require('nock');
 
 const bootstrap = require('../test_helper');
 
-const fail = () => { throw new Error('expected promise to be rejected'); };
-
 describe('Back-Channel Logout 1.0', () => {
   before(bootstrap(__dirname));
 
@@ -61,8 +60,8 @@ describe('Back-Channel Logout 1.0', () => {
         .post('/backchannel_logout')
         .reply(500);
 
-      return client.backchannelLogout('subject', 'foo').then(fail, (err) => {
-        expect(err.message).to.eql('expected 200 OK from https://no-sid.example.com/backchannel_logout, got: 500 Internal Server Error');
+      return assert.rejects(client.backchannelLogout('subject', 'foo'), {
+        message: 'expected 200 OK from https://no-sid.example.com/backchannel_logout, got: 500 Internal Server Error',
       });
     });
   });
diff --git a/test/base_token/base_token.test.js b/test/base_token/base_token.test.js
index db5e1be1b..6079d4421 100644
--- a/test/base_token/base_token.test.js
+++ b/test/base_token/base_token.test.js
@@ -1,11 +1,11 @@
+const { strict: assert } = require('assert');
+
 const sinon = require('sinon').createSandbox();
 const { expect } = require('chai');
 const timekeeper = require('timekeeper');
 
 const bootstrap = require('../test_helper');
 
-const fail = () => { throw new Error('expected promise to be rejected'); };
-
 describe('BaseToken', () => {
   before(bootstrap(__dirname));
 
@@ -136,9 +136,10 @@ describe('BaseToken', () => {
     const value = await token.save();
     const adapterThrow = new Error('adapter throw!');
     sinon.stub(this.TestAdapter.for('Session'), 'findByUid').callsFake(async () => { throw adapterThrow; });
-    await this.provider.RefreshToken.find(value).then(fail, (err) => {
+    return assert.rejects(this.provider.RefreshToken.find(value), (err) => {
       this.TestAdapter.for('Session').findByUid.restore();
       expect(err).to.equal(adapterThrow);
+      return true;
     });
   });
 
@@ -156,12 +157,12 @@ describe('BaseToken', () => {
   it('rethrows adapter#findByUserCode errors (Device Code)', async function () {
     const adapterThrow = new Error('adapter throw!');
     sinon.stub(this.TestAdapter.for('DeviceCode'), 'findByUserCode').callsFake(async () => { throw adapterThrow; });
-    await this.provider.DeviceCode.findByUserCode('123-456-789').then(() => {
+    return assert.rejects(this.provider.DeviceCode.findByUserCode('123-456-789').then(() => {
       this.TestAdapter.for('DeviceCode').findByUserCode.restore();
-      fail();
-    }, (err) => {
+    }), (err) => {
       this.TestAdapter.for('DeviceCode').findByUserCode.restore();
       expect(err).to.equal(adapterThrow);
+      return true;
     });
   });
 });
diff --git a/test/configuration/client_keystore.test.js b/test/configuration/client_keystore.test.js
index d74b8c060..b042d7b0a 100644
--- a/test/configuration/client_keystore.test.js
+++ b/test/configuration/client_keystore.test.js
@@ -10,8 +10,6 @@ const JWT = require('../../lib/helpers/jwt');
 const epochTime = require('../../lib/helpers/epoch_time');
 const bootstrap = require('../test_helper');
 
-const fail = () => { throw new Error('expected promise to be rejected'); };
-
 const endpoint = nock('https://client.example.com/');
 const keystore = new jose.JWKS.KeyStore();
 
@@ -63,15 +61,17 @@ describe('client keystore refresh', () => {
     const client = await this.provider.Client.find('client');
     sinon.stub(client.asymmetricKeyStore, 'fresh').returns(false);
     return Promise.all([
-      client.asymmetricKeyStore.refresh().then(fail, (err) => {
+      assert.rejects(client.asymmetricKeyStore.refresh(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('invalid_client_metadata');
         expect(err.error_description).to.eql('client JSON Web Key Set failed to be refreshed');
+        return true;
       }),
-      client.asymmetricKeyStore.refresh().then(fail, (err) => {
+      assert.rejects(client.asymmetricKeyStore.refresh(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('invalid_client_metadata');
         expect(err.error_description).to.eql('client JSON Web Key Set failed to be refreshed');
+        return true;
       }),
     ]);
   });
@@ -101,10 +101,11 @@ describe('client keystore refresh', () => {
 
     const client = await this.provider.Client.find('client');
     sinon.stub(client.asymmetricKeyStore, 'fresh').returns(false);
-    await client.asymmetricKeyStore.refresh().then(fail, (err) => {
+    return assert.rejects(client.asymmetricKeyStore.refresh(), (err) => {
       expect(err).to.be.an('error');
       expect(err.message).to.equal('invalid_client_metadata');
       expect(err.error_description).to.eql('client JSON Web Key Set failed to be refreshed');
+      return true;
     });
   });
 
@@ -113,10 +114,11 @@ describe('client keystore refresh', () => {
 
     const client = await this.provider.Client.find('client');
     sinon.stub(client.asymmetricKeyStore, 'fresh').returns(false);
-    await client.asymmetricKeyStore.refresh().then(fail, (err) => {
+    return assert.rejects(client.asymmetricKeyStore.refresh(), (err) => {
       expect(err).to.be.an('error');
       expect(err.message).to.equal('invalid_client_metadata');
       expect(err.error_description).to.eql('client JSON Web Key Set failed to be refreshed');
+      return true;
     });
   });
 
@@ -125,10 +127,11 @@ describe('client keystore refresh', () => {
 
     const client = await this.provider.Client.find('client');
     sinon.stub(client.asymmetricKeyStore, 'fresh').returns(false);
-    await client.asymmetricKeyStore.refresh().then(fail, (err) => {
+    return assert.rejects(client.asymmetricKeyStore.refresh(), (err) => {
       expect(err).to.be.an('error');
       expect(err.message).to.equal('invalid_client_metadata');
       expect(err.error_description).to.eql('client JSON Web Key Set failed to be refreshed');
+      return true;
     });
   });
 
@@ -225,10 +228,10 @@ describe('client keystore refresh', () => {
 
       const client = await this.provider.Client.find('client');
       client.asymmetricKeyStore.freshUntil = epochTime() - 1;
-      await JWT.verify(
+      return assert.rejects(JWT.verify(
         'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWV9.TJVA95OrM7E2cBab30RMHrHDcEfxjoYZgeFONFh7HgA',
         client.asymmetricKeyStore,
-      ).then(fail, () => {});
+      ));
     });
 
     it('refreshes stale keystores before id_token encryption', async function () {
diff --git a/test/configuration/client_metadata.test.js b/test/configuration/client_metadata.test.js
index f6c7ecb8e..1c1f9688f 100644
--- a/test/configuration/client_metadata.test.js
+++ b/test/configuration/client_metadata.test.js
@@ -1,3 +1,4 @@
+const { strict: assert } = require('assert');
 const util = require('util');
 
 const { expect } = require('chai');
@@ -43,29 +44,29 @@ describe('Client metadata validation', () => {
     });
   }
 
-  const fail = () => { throw new Error('expected promise to be rejected'); };
-
   const mustBeString = (prop, values = [[], 123, true, null, false, {}, ''], metadata, configuration) => {
     values.forEach((value) => {
       let msg = util.format('must be a string, %j provided', value);
       if (metadata) msg = util.format(`${msg}, [client %j]`, omit(metadata, ['jwks.keys']));
       if (configuration) msg = util.format(`${msg}, [provider %j]`, configuration);
-      it(msg, () => addClient({ ...metadata, [prop]: value }, configuration).then(fail, (err) => {
+      // eslint-disable-next-line max-len
+      it(msg, () => assert.rejects(addClient({ ...metadata, [prop]: value }, configuration), (err) => {
         if (prop === 'redirect_uris') {
           expect(err.message).to.equal('invalid_redirect_uri');
         } else {
           expect(err.message).to.equal('invalid_client_metadata');
         }
         expect(err.error_description).to.equal(`${prop} must be a non-empty string if provided`);
+        return true;
       }));
     });
   };
 
   const mustBeUri = (prop, protocols, configuration, metadata) => {
-    it('must be a uri', () => addClient({
+    it('must be a uri', () => assert.rejects(addClient({
       ...metadata,
       [prop]: 'whatever://not but not a uri',
-    }, configuration).then(fail, (err) => {
+    }, configuration), (err) => {
       if (prop === 'redirect_uris') {
         expect(err.message).to.equal('invalid_redirect_uri');
       } else {
@@ -76,6 +77,7 @@ describe('Client metadata validation', () => {
       } else {
         expect(err.error_description).to.equal(`${prop} must be a web uri`);
       }
+      return true;
     }));
 
     protocols.forEach((protocol) => {
@@ -89,15 +91,16 @@ describe('Client metadata validation', () => {
     values.forEach((value) => {
       let msg = util.format('must be a array, %j provided', value);
       if (configuration) msg = util.format(`${msg}, [provider %j]`, configuration);
-      it(msg, () => addClient({
+      it(msg, () => assert.rejects(addClient({
         [prop]: value,
-      }, configuration).then(fail, (err) => {
+      }, configuration), (err) => {
         if (prop === 'redirect_uris') {
           expect(err.message).to.equal('invalid_redirect_uri');
         } else {
           expect(err.message).to.equal('invalid_client_metadata');
         }
         expect(err.error_description).to.equal(`${prop} must be an array`);
+        return true;
       }));
     });
   };
@@ -107,15 +110,16 @@ describe('Client metadata validation', () => {
       let msg = util.format('must be a boolean, %j provided', value);
       if (metadata) msg = util.format(`${msg}, [client %j]`, omit(metadata, ['jwks.keys']));
       if (configuration) msg = util.format(`${msg}, [provider %j]`, configuration);
-      it(msg, () => addClient({
+      it(msg, () => assert.rejects(addClient({
         [prop]: value,
-      }, configuration).then(fail, (err) => {
+      }, configuration), (err) => {
         if (prop === 'redirect_uris') {
           expect(err.message).to.equal('invalid_redirect_uri');
         } else {
           expect(err.message).to.equal('invalid_client_metadata');
         }
         expect(err.error_description).to.equal(`${prop} must be a boolean`);
+        return true;
       }));
     });
   };
@@ -138,16 +142,17 @@ describe('Client metadata validation', () => {
     (values || [null, undefined, '']).forEach((value) => {
       let msg = util.format('is required, %j provided', value);
       if (configuration) msg = util.format(`${msg}, [provider %j]`, configuration);
-      it(msg, () => addClient({
+      it(msg, () => assert.rejects(addClient({
         [prop]: value,
         ...metadata,
-      }, configuration).then(fail, (err) => {
+      }, configuration), (err) => {
         if (prop === 'redirect_uris') {
           expect(err.message).to.equal('invalid_redirect_uri');
         } else {
           expect(err.message).to.equal('invalid_client_metadata');
         }
         expect(err.error_description).to.equal(`${prop} is mandatory property`);
+        return true;
       }));
     });
   };
@@ -171,16 +176,17 @@ describe('Client metadata validation', () => {
     let msg = util.format('rejects %j', value);
     if (metadata) msg = util.format(`${msg}, [client %j]`, omit(metadata, ['jwks.keys']));
     if (configuration) msg = util.format(`${msg}, [provider %j]`, configuration);
-    it(msg, () => addClient({ ...metadata, [prop]: value }, configuration).then(fail, (err) => {
+    // eslint-disable-next-line max-len
+    it(msg, () => assert.rejects(addClient({ ...metadata, [prop]: value }, configuration), (err) => {
       if (prop === 'redirect_uris') {
         expect(err.message).to.equal('invalid_redirect_uri');
       } else {
         expect(err.message).to.equal('invalid_client_metadata');
       }
       if (description) {
-        const assert = description.exec ? 'match' : 'equal';
-        expect(err.error_description).to[assert](description);
+        expect(err.error_description).to[description.exec ? 'match' : 'equal'](description);
       }
+      return true;
     }));
   };
 
@@ -636,11 +642,12 @@ describe('Client metadata validation', () => {
       mustBeString(this.title, undefined, {
         jwks: { keys: [sigKey] },
       }, configuration);
-      it('is required when id_token_encrypted_response_enc is also provided', () => addClient({
+      it('is required when id_token_encrypted_response_enc is also provided', () => assert.rejects(addClient({
         id_token_encrypted_response_enc: 'whatever',
-      }, configuration).then(fail, (err) => {
+      }, configuration), (err) => {
         expect(err.message).to.equal('invalid_client_metadata');
         expect(err.error_description).to.equal('id_token_encrypted_response_alg is mandatory property when id_token_encrypted_response_enc is provided');
+        return true;
       }));
       allows(this.title, 'dir', undefined, configuration);
       [
@@ -688,11 +695,12 @@ describe('Client metadata validation', () => {
       mustBeString(this.title, undefined, {
         jwks: { keys: [sigKey] },
       }, configuration);
-      it('is required when userinfo_encrypted_response_enc is also provided', () => addClient({
+      it('is required when userinfo_encrypted_response_enc is also provided', () => assert.rejects(addClient({
         userinfo_encrypted_response_enc: 'whatever',
-      }, configuration).then(fail, (err) => {
+      }, configuration), (err) => {
         expect(err.message).to.equal('invalid_client_metadata');
         expect(err.error_description).to.equal('userinfo_encrypted_response_alg is mandatory property when userinfo_encrypted_response_enc is provided');
+        return true;
       }));
       allows(this.title, 'dir', undefined, configuration);
       [
@@ -741,11 +749,12 @@ describe('Client metadata validation', () => {
       mustBeString(this.title, undefined, {
         jwks: { keys: [sigKey] },
       }, configuration);
-      it('is required when introspection_encrypted_response_enc is also provided', () => addClient({
+      it('is required when introspection_encrypted_response_enc is also provided', () => assert.rejects(addClient({
         introspection_encrypted_response_enc: 'whatever',
-      }, configuration).then(fail, (err) => {
+      }, configuration), (err) => {
         expect(err.message).to.equal('invalid_client_metadata');
         expect(err.error_description).to.equal('introspection_encrypted_response_alg is mandatory property when introspection_encrypted_response_enc is provided');
+        return true;
       }));
       allows(this.title, 'dir', undefined, configuration);
       [
@@ -794,11 +803,12 @@ describe('Client metadata validation', () => {
       mustBeString(this.title, undefined, {
         jwks: { keys: [sigKey] },
       }, configuration);
-      it('is required when authorization_encrypted_response_enc is also provided', () => addClient({
+      it('is required when authorization_encrypted_response_enc is also provided', () => assert.rejects(addClient({
         authorization_encrypted_response_enc: 'whatever',
-      }, configuration).then(fail, (err) => {
+      }, configuration), (err) => {
         expect(err.message).to.equal('invalid_client_metadata');
         expect(err.error_description).to.equal('authorization_encrypted_response_alg is mandatory property when authorization_encrypted_response_enc is provided');
+        return true;
       }));
       allows(this.title, 'dir', undefined, configuration);
       [
@@ -853,11 +863,12 @@ describe('Client metadata validation', () => {
       defaultsTo(this.title, undefined);
       defaultsTo(this.title, undefined, undefined, configuration);
       mustBeString(this.title, undefined, undefined, configuration);
-      it('is required when request_object_encryption_enc is also provided', () => addClient({
+      it('is required when request_object_encryption_enc is also provided', () => assert.rejects(addClient({
         request_object_encryption_enc: 'whatever',
-      }, configuration).then(fail, (err) => {
+      }, configuration), (err) => {
         expect(err.message).to.equal('invalid_client_metadata');
         expect(err.error_description).to.equal('request_object_encryption_alg is mandatory property when request_object_encryption_enc is provided');
+        return true;
       }));
       allows(this.title, 'dir', undefined, configuration);
       [
diff --git a/test/formats/jwt.test.js b/test/formats/jwt.test.js
index f7b791894..63d29d783 100644
--- a/test/formats/jwt.test.js
+++ b/test/formats/jwt.test.js
@@ -1,5 +1,6 @@
 /* eslint-disable no-shadow */
 /* eslint-disable no-param-reassign */
+const { strict: assert } = require('assert');
 const crypto = require('crypto');
 const util = require('util');
 
@@ -10,7 +11,6 @@ const base64url = require('base64url');
 const epochTime = require('../../lib/helpers/epoch_time');
 const bootstrap = require('../test_helper');
 
-const fail = () => { throw new Error('expected promise to be rejected'); };
 const generateKeyPair = util.promisify(crypto.generateKeyPair);
 function decode(b64urljson) {
   return JSON.parse(base64url.decode(b64urljson));
@@ -142,9 +142,10 @@ describe('jwt format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('jwt.sign.kid must be a string when provided');
+        return true;
       });
     });
 
@@ -164,9 +165,10 @@ describe('jwt format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('jwt.encrypt.kid must be a string when provided');
+        return true;
       });
     });
 
@@ -348,9 +350,10 @@ describe('jwt format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('JWT Access Tokens may not use JWS algorithm "none"');
+        return true;
       });
     });
 
@@ -367,9 +370,10 @@ describe('jwt format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('missing jwt.sign.key Resource Server configuration');
+        return true;
       });
     });
 
@@ -387,9 +391,10 @@ describe('jwt format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('jwt.sign.key Resource Server configuration must be a secret (symmetric) key');
+        return true;
       });
     });
 
@@ -407,9 +412,10 @@ describe('jwt format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('jwt.sign.key Resource Server configuration must be a secret (symmetric) key');
+        return true;
       });
     });
 
@@ -426,9 +432,10 @@ describe('jwt format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('resolved Resource Server jwt configuration has no corresponding key in the provider\'s keystore');
+        return true;
       });
     });
 
@@ -447,9 +454,10 @@ describe('jwt format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('jwt.encrypt.key Resource Server configuration must be a secret (symmetric) or a public key');
+        return true;
       });
     });
 
@@ -468,14 +476,16 @@ describe('jwt format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('missing jwt.sign Resource Server configuration');
+        return true;
       });
     });
 
     // eslint-disable-next-line no-restricted-syntax
     for (const prop of ['alg', 'enc', 'key']) {
+      // eslint-disable-next-line no-loop-func
       it(`ensures JWE Configuration has ${prop}`, async function () {
         const resourceServer = {
           accessTokenFormat: 'jwt',
@@ -493,9 +503,10 @@ describe('jwt format', () => {
 
         const client = await this.provider.Client.find(clientId);
         const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-        await token.save().then(fail, (err) => {
+        return assert.rejects(token.save(), (err) => {
           expect(err).to.be.an('error');
           expect(err.message).to.equal(`missing jwt.encrypt.${prop} Resource Server configuration`);
+          return true;
         });
       });
     }
diff --git a/test/formats/paseto.test.js b/test/formats/paseto.test.js
index c1eef9619..4137a1805 100644
--- a/test/formats/paseto.test.js
+++ b/test/formats/paseto.test.js
@@ -1,5 +1,6 @@
 /* eslint-disable no-shadow */
 /* eslint-disable no-param-reassign */
+const { strict: assert } = require('assert');
 const crypto = require('crypto');
 const util = require('util');
 
@@ -10,7 +11,6 @@ const paseto = require('paseto');
 const epochTime = require('../../lib/helpers/epoch_time');
 const bootstrap = require('../test_helper');
 
-const fail = () => { throw new Error('expected promise to be rejected'); };
 const generateKeyPair = util.promisify(crypto.generateKeyPair);
 
 describe('paseto format', () => {
@@ -141,9 +141,10 @@ describe('paseto format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('unsupported PASETO version and purpose');
+        return true;
       });
     });
 
@@ -160,9 +161,10 @@ describe('paseto format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('resolved Resource Server paseto configuration has no corresponding key in the provider\'s keystore');
+        return true;
       });
     });
 
@@ -180,9 +182,10 @@ describe('paseto format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('paseto.kid must be a string when provided');
+        return true;
       });
     });
 
@@ -198,9 +201,10 @@ describe('paseto format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('unsupported PASETO version and purpose');
+        return true;
       });
     });
 
@@ -216,9 +220,10 @@ describe('paseto format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('unsupported "paseto.version"');
+        return true;
       });
     });
 
@@ -234,9 +239,10 @@ describe('paseto format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('local purpose PASETO Resource Server requires a "paseto.key"');
+        return true;
       });
     });
 
@@ -253,9 +259,10 @@ describe('paseto format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('local purpose PASETO Resource Server "paseto.key" must be 256 bits long secret key');
+        return true;
       });
     });
 
@@ -272,9 +279,10 @@ describe('paseto format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('local purpose PASETO Resource Server "paseto.key" must be 256 bits long secret key');
+        return true;
       });
     });
 
@@ -291,9 +299,10 @@ describe('paseto format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('local purpose PASETO Resource Server "paseto.key" must be 256 bits long secret key');
+        return true;
       });
     });
 
@@ -305,9 +314,10 @@ describe('paseto format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('missing "paseto" Resource Server configuration');
+        return true;
       });
     });
 
@@ -320,9 +330,10 @@ describe('paseto format', () => {
 
       const client = await this.provider.Client.find(clientId);
       const token = new this.provider.AccessToken({ client, ...fullPayload, resourceServer });
-      await token.save().then(fail, (err) => {
+      return assert.rejects(token.save(), (err) => {
         expect(err).to.be.an('error');
         expect(err.message).to.equal('missing "paseto" Resource Server configuration');
+        return true;
       });
     });
   });
diff --git a/test/interaction/interaction.test.js b/test/interaction/interaction.test.js
index a8fa44cad..44cc46d2d 100644
--- a/test/interaction/interaction.test.js
+++ b/test/interaction/interaction.test.js
@@ -1,5 +1,7 @@
 /* eslint-disable no-underscore-dangle */
 
+const { strict: assert } = require('assert');
+
 const { expect } = require('chai');
 const KeyGrip = require('keygrip'); // eslint-disable-line import/no-extraneous-dependencies
 const sinon = require('sinon').createSandbox();
@@ -11,7 +13,6 @@ const epochTime = require('../../lib/helpers/epoch_time');
 const expire = new Date();
 expire.setDate(expire.getDate() + 1);
 const expired = new Date(0);
-const fail = () => { throw new Error('expected promise to be rejected'); };
 
 function handlesInteractionSessionErrors() {
   it('"handles" not found interaction session id cookie', async function () {
@@ -24,9 +25,10 @@ function handlesInteractionSessionErrors() {
     sinon.spy(this.provider, 'interactionDetails');
 
     await this.agent.get(this.url).expect(400);
-    await this.provider.interactionDetails.getCall(0).returnValue.then(fail, (err) => {
+    return assert.rejects(this.provider.interactionDetails.getCall(0).returnValue, (err) => {
       expect(err.name).to.eql('SessionNotFound');
       expect(err.error_description).to.eql('interaction session id cookie not found');
+      return true;
     });
   });
 
@@ -36,9 +38,10 @@ function handlesInteractionSessionErrors() {
     sinon.spy(this.provider, 'interactionDetails');
 
     await this.agent.get(this.url).expect(400);
-    await this.provider.interactionDetails.getCall(0).returnValue.then(fail, (err) => {
+    return assert.rejects(this.provider.interactionDetails.getCall(0).returnValue, (err) => {
       expect(err.name).to.eql('SessionNotFound');
       expect(err.error_description).to.eql('interaction session not found');
+      return true;
     });
   });
 }
diff --git a/test/oauth_native_apps/oauth_native_apps.test.js b/test/oauth_native_apps/oauth_native_apps.test.js
index 68b2ae2d4..961d276c8 100644
--- a/test/oauth_native_apps/oauth_native_apps.test.js
+++ b/test/oauth_native_apps/oauth_native_apps.test.js
@@ -1,9 +1,9 @@
+const { strict: assert } = require('assert');
+
 const { expect } = require('chai');
 
 const bootstrap = require('../test_helper');
 
-const fail = () => { throw new Error('expected promise to be rejected'); };
-
 describe('OAuth 2.0 for Native Apps Best Current Practice features', () => {
   before(bootstrap(__dirname));
 
@@ -21,16 +21,17 @@ describe('OAuth 2.0 for Native Apps Best Current Practice features', () => {
       });
 
       it('rejects custom schemes without dots with reverse domain name scheme recommendation', function () {
-        return i(this.provider).clientAdd({
+        return assert.rejects(i(this.provider).clientAdd({
           application_type: 'native',
           client_id: 'native-custom',
           grant_types: ['implicit'],
           response_types: ['id_token'],
           token_endpoint_auth_method: 'none',
           redirect_uris: ['myapp:/op/callback'],
-        }).then(fail, (err) => {
+        }), (err) => {
           expect(err).to.have.property('message', 'invalid_redirect_uri');
           expect(err).to.have.property('error_description', 'redirect_uris for native clients using Custom URI scheme should use reverse domain name based scheme');
+          return true;
         });
       });
     });
@@ -48,16 +49,17 @@ describe('OAuth 2.0 for Native Apps Best Current Practice features', () => {
       });
 
       it('rejects https if using loopback uris', function () {
-        return i(this.provider).clientAdd({
+        return assert.rejects(i(this.provider).clientAdd({
           application_type: 'native',
           client_id: 'native-custom',
           grant_types: ['implicit'],
           response_types: ['id_token'],
           token_endpoint_auth_method: 'none',
           redirect_uris: ['https://localhost/op/callback'],
-        }).then(fail, (err) => {
+        }), (err) => {
           expect(err).to.have.property('message', 'invalid_redirect_uri');
           expect(err).to.have.property('error_description', 'redirect_uris for native clients using claimed HTTPS URIs must not be using localhost as hostname');
+          return true;
         });
       });
     });
@@ -187,16 +189,17 @@ describe('OAuth 2.0 for Native Apps Best Current Practice features', () => {
       });
 
       it('rejects http protocol uris not using loopback uris', function () {
-        return i(this.provider).clientAdd({
+        return assert.rejects(i(this.provider).clientAdd({
           application_type: 'native',
           client_id: 'native-custom',
           grant_types: ['implicit'],
           response_types: ['id_token'],
           token_endpoint_auth_method: 'none',
           redirect_uris: ['http://rp.example.com/op/callback'],
-        }).then(fail, (err) => {
+        }), (err) => {
           expect(err).to.have.property('message', 'invalid_redirect_uri');
           expect(err).to.have.property('error_description', 'redirect_uris for native clients using http as a protocol can only use loopback addresses as hostnames');
+          return true;
         });
       });
     });
diff --git a/test/pairwise/pairwise_clients.test.js b/test/pairwise/pairwise_clients.test.js
index f6bd6ecec..73c243048 100644
--- a/test/pairwise/pairwise_clients.test.js
+++ b/test/pairwise/pairwise_clients.test.js
@@ -5,8 +5,6 @@ const nock = require('nock');
 
 const bootstrap = require('../test_helper');
 
-const j = JSON.stringify;
-
 describe('pairwise features', () => {
   before(bootstrap(__dirname));
 
@@ -58,7 +56,7 @@ describe('pairwise features', () => {
       it('is not ignored even without subject_type=pairwise', function () {
         nock('https://foobar.example.com')
           .get('/sector')
-          .reply(200, j(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
+          .reply(200, JSON.stringify(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
 
         return i(this.provider).clientAdd({
           client_id: 'client',
@@ -75,7 +73,7 @@ describe('pairwise features', () => {
       it('validates the sector from the provided uri', function () {
         nock('https://foobar.example.com')
           .get('/sector')
-          .reply(200, j(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
+          .reply(200, JSON.stringify(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
 
         return i(this.provider).clientAdd({
           client_id: 'client',
@@ -92,7 +90,7 @@ describe('pairwise features', () => {
       it('validates the sector from the provided uri for static clients too', function () {
         nock('https://foobar.example.com')
           .get('/sector')
-          .reply(200, j(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
+          .reply(200, JSON.stringify(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
 
         return this.provider.Client.find('client-static-with-sector').then((client) => {
           expect(client).to.be.ok;
@@ -118,7 +116,7 @@ describe('pairwise features', () => {
       it('validates all redirect_uris are in the uri', function () {
         nock('https://client.example.com')
           .get('/sector')
-          .reply(200, j(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
+          .reply(200, JSON.stringify(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
 
         return i(this.provider).clientAdd({
           client_id: 'client',
@@ -139,7 +137,7 @@ describe('pairwise features', () => {
         it('validates jwks_uri is in the response', function () {
           nock('https://client.example.com')
             .get('/sector')
-            .reply(200, j(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
+            .reply(200, JSON.stringify(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
 
           return i(this.provider).clientAdd({
             client_id: 'client',
@@ -164,7 +162,7 @@ describe('pairwise features', () => {
         it('validates jwks_uri is in the response', function () {
           nock('https://client.example.com')
             .get('/sector')
-            .reply(200, j(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
+            .reply(200, JSON.stringify(['https://client.example.com/cb', 'https://another.example.com/forum/cb']));
 
           return i(this.provider).clientAdd({
             client_id: 'client',
@@ -207,7 +205,7 @@ describe('pairwise features', () => {
       it('validates only accepts json array responses', function () {
         nock('https://client.example.com')
           .get('/sector')
-          .reply(200, j('https://client.example.com/cb'));
+          .reply(200, JSON.stringify('https://client.example.com/cb'));
 
         return i(this.provider).clientAdd({
           client_id: 'client',
@@ -247,7 +245,7 @@ describe('pairwise features', () => {
       it('doesnt accepts 200s, rejects even on redirect', function () {
         nock('https://client.example.com')
           .get('/sector')
-          .reply(201, j('https://client.example.com/cb'));
+          .reply(201, JSON.stringify('https://client.example.com/cb'));
 
         return i(this.provider).clientAdd({
           client_id: 'client',
diff --git a/test/refresh/refresh.grant.test.js b/test/refresh/refresh.grant.test.js
index 536595c92..b30b8ce48 100644
--- a/test/refresh/refresh.grant.test.js
+++ b/test/refresh/refresh.grant.test.js
@@ -1,3 +1,4 @@
+const { strict: assert } = require('assert');
 const { parse: parseUrl } = require('url');
 
 const sinon = require('sinon');
@@ -7,8 +8,6 @@ const timekeeper = require('timekeeper');
 
 const bootstrap = require('../test_helper');
 
-const fail = () => { throw new Error('expected promise to be rejected'); };
-const j = JSON.parse;
 const route = '/token';
 
 function errorDetail(spy) {
@@ -84,7 +83,7 @@ describe('grant_type=refresh_token', () => {
       })
       .expect(({ body }) => {
         expect(body).to.have.keys('access_token', 'id_token', 'expires_in', 'token_type', 'refresh_token', 'scope');
-        const refreshIdToken = j(base64url.decode(body.id_token.split('.')[1]));
+        const refreshIdToken = JSON.parse(base64url.decode(body.id_token.split('.')[1]));
         expect(refreshIdToken).to.have.property('nonce', 'foobarnonce');
         expect(body).to.have.property('refresh_token').that.is.a('string');
       });
@@ -365,7 +364,7 @@ describe('grant_type=refresh_token', () => {
         })
         .expect((response) => {
           expect(response.body).to.have.keys('access_token', 'id_token', 'expires_in', 'token_type', 'refresh_token', 'scope');
-          const refreshIdToken = j(base64url.decode(response.body.id_token.split('.')[1]));
+          const refreshIdToken = JSON.parse(base64url.decode(response.body.id_token.split('.')[1]));
           expect(refreshIdToken).to.have.property('nonce', 'foobarnonce');
           expect(response.body).to.have.property('refresh_token').not.equal(rt);
         });
@@ -431,7 +430,7 @@ describe('grant_type=refresh_token', () => {
       this.provider.on('grant.revoked', grantRevokeSpy);
       this.provider.on('refresh_token.destroyed', tokenDestroySpy);
 
-      return Promise.all([
+      return assert.rejects(Promise.all([
         this.agent.post(route)
           .auth('client', 'secret')
           .send({
@@ -448,9 +447,10 @@ describe('grant_type=refresh_token', () => {
           })
           .type('form')
           .expect(200), // one of them will fail.
-      ]).then(fail, () => {
+      ]), () => {
         expect(grantRevokeSpy.calledOnce).to.be.true;
         expect(tokenDestroySpy.calledOnce).to.be.true;
+        return true;
       });
     });
   });
@@ -506,7 +506,7 @@ describe('grant_type=refresh_token', () => {
         })
         .expect((response) => {
           expect(response.body).to.have.keys('access_token', 'id_token', 'expires_in', 'token_type', 'refresh_token', 'scope');
-          const refreshIdToken = j(base64url.decode(response.body.id_token.split('.')[1]));
+          const refreshIdToken = JSON.parse(base64url.decode(response.body.id_token.split('.')[1]));
           expect(refreshIdToken).to.have.property('nonce', 'foobarnonce');
           expect(response.body).to.have.property('refresh_token').not.equal(rt);
         });
@@ -570,7 +570,7 @@ describe('grant_type=refresh_token', () => {
       this.provider.on('grant.revoked', grantRevokeSpy);
       this.provider.on('refresh_token.destroyed', tokenDestroySpy);
 
-      return Promise.all([
+      return assert.rejects(Promise.all([
         this.agent.post(route)
           .auth('client', 'secret')
           .send({
@@ -587,9 +587,10 @@ describe('grant_type=refresh_token', () => {
           })
           .type('form')
           .expect(200), // one of them will fail.
-      ]).then(fail, () => {
+      ]), () => {
         expect(grantRevokeSpy.calledOnce).to.be.true;
         expect(tokenDestroySpy.calledOnce).to.be.true;
+        return true;
       });
     });
   });
@@ -622,7 +623,7 @@ describe('grant_type=refresh_token', () => {
         .expect(200)
         .expect(({ body }) => {
           expect(body).to.have.keys('access_token', 'id_token', 'expires_in', 'token_type', 'refresh_token', 'scope');
-          const refreshIdToken = j(base64url.decode(body.id_token.split('.')[1]));
+          const refreshIdToken = JSON.parse(base64url.decode(body.id_token.split('.')[1]));
           expect(refreshIdToken).to.have.property('nonce', 'foobarnonce');
           expect(body).to.have.property('refresh_token').that.is.a('string');
         })
diff --git a/test/registration_policies/registration_policies.test.js b/test/registration_policies/registration_policies.test.js
index d8fd776c5..339ab5632 100644
--- a/test/registration_policies/registration_policies.test.js
+++ b/test/registration_policies/registration_policies.test.js
@@ -1,5 +1,6 @@
-/* eslint-disable no-param-reassign */
+/* eslint-disable no-param-reassign, max-len */
 
+const { strict: assert } = require('assert');
 const url = require('url');
 
 const sinon = require('sinon').createSandbox();
@@ -8,8 +9,6 @@ const { expect } = require('chai');
 const bootstrap = require('../test_helper');
 const { Provider } = require('../../lib');
 
-const fail = () => { throw new Error('expected promise to be rejected'); };
-
 describe('client registration policies', () => {
   before(bootstrap(__dirname));
   beforeEach(sinon.restore);
@@ -147,58 +146,66 @@ describe('client registration policies', () => {
     });
 
     it('policies must be an array', async function () {
-      await new this.provider.InitialAccessToken({ policies: null }).save().then(fail, (err) => {
+      await assert.rejects(new this.provider.InitialAccessToken({ policies: null }).save(), (err) => {
         expect(err).to.have.property('message', 'policies must be an array');
+        return true;
       });
       const saved = await new this.provider.InitialAccessToken({ policies: undefined }).save();
       this.TestAdapter.for('InitialAccessToken').syncUpdate(this.getTokenJti(saved), {
         policies: null,
       });
 
-      await this.provider.InitialAccessToken.find(saved).then(fail, (err) => {
+      return assert.rejects(this.provider.InitialAccessToken.find(saved), (err) => {
         expect(err).to.have.property('message', 'policies must be an array');
+        return true;
       });
     });
 
     it('policies array must have members', async function () {
-      await new this.provider.InitialAccessToken({ policies: [] }).save().then(fail, (err) => {
+      await assert.rejects(new this.provider.InitialAccessToken({ policies: [] }).save(), (err) => {
         expect(err).to.have.property('message', 'policies must not be empty');
+        return true;
       });
       const saved = await new this.provider.InitialAccessToken({ policies: undefined }).save();
       this.TestAdapter.for('InitialAccessToken').syncUpdate(this.getTokenJti(saved), {
         policies: [],
       });
 
-      await this.provider.InitialAccessToken.find(saved).then(fail, (err) => {
+      return assert.rejects(this.provider.InitialAccessToken.find(saved), (err) => {
         expect(err).to.have.property('message', 'policies must not be empty');
+        return true;
       });
     });
 
     it('policies members must be strings', async function () {
-      await new this.provider.InitialAccessToken({ policies: [null] }).save().then(fail, (err) => {
+      await assert.rejects(new this.provider.InitialAccessToken({ policies: [null] }).save(), (err) => {
         expect(err).to.have.property('message', 'policies must be strings');
+        return true;
       });
       const saved = await new this.provider.InitialAccessToken({ policies: undefined }).save();
       this.TestAdapter.for('InitialAccessToken').syncUpdate(this.getTokenJti(saved), {
         policies: [null],
       });
 
-      await this.provider.InitialAccessToken.find(saved).then(fail, (err) => {
+      return assert.rejects(this.provider.InitialAccessToken.find(saved), (err) => {
         expect(err).to.have.property('message', 'policies must be strings');
+        return true;
       });
     });
 
     it('policies members must be present in the provider configuration', async function () {
-      await new this.provider.InitialAccessToken({ policies: ['foo-bar'] }).save().then(fail, (err) => {
+      await assert.rejects(new this.provider.InitialAccessToken({ policies: ['foo-bar'] }).save(), (err) => {
         expect(err).to.have.property('message', 'policy foo-bar not configured');
+        return true;
       });
       const saved = await new this.provider.InitialAccessToken({ policies: undefined }).save();
       this.TestAdapter.for('InitialAccessToken').syncUpdate(this.getTokenJti(saved), {
         policies: ['foo-bar'],
       });
 
-      await this.provider.InitialAccessToken.find(saved).then(fail, (err) => {
+      return assert.rejects(this.provider.InitialAccessToken.find(saved), (err) => {
         expect(err).to.have.property('message', 'policy foo-bar not configured');
+        return true;
       });
     });
   });
@@ -354,8 +361,9 @@ describe('client registration policies', () => {
         policies: null,
       });
 
-      await this.provider.RegistrationAccessToken.find(saved).then(fail, (err) => {
+      return assert.rejects(this.provider.RegistrationAccessToken.find(saved), (err) => {
         expect(err).to.have.property('message', 'policies must be an array');
+        return true;
       });
     });
 
@@ -365,8 +373,9 @@ describe('client registration policies', () => {
         policies: [],
       });
 
-      await this.provider.RegistrationAccessToken.find(saved).then(fail, (err) => {
+      return assert.rejects(this.provider.RegistrationAccessToken.find(saved), (err) => {
         expect(err).to.have.property('message', 'policies must not be empty');
+        return true;
       });
     });
 
@@ -376,8 +385,9 @@ describe('client registration policies', () => {
         policies: [null],
       });
 
-      await this.provider.RegistrationAccessToken.find(saved).then(fail, (err) => {
+      return assert.rejects(this.provider.RegistrationAccessToken.find(saved), (err) => {
         expect(err).to.have.property('message', 'policies must be strings');
+        return true;
       });
     });
 
@@ -387,8 +397,9 @@ describe('client registration policies', () => {
         policies: ['foo-bar'],
       });
 
-      await this.provider.RegistrationAccessToken.find(saved).then(fail, (err) => {
+      return assert.rejects(this.provider.RegistrationAccessToken.find(saved), (err) => {
         expect(err).to.have.property('message', 'policy foo-bar not configured');
+        return true;
       });
     });
   });
diff --git a/test/resource_indicators/resource_indicators.test.js b/test/resource_indicators/resource_indicators.test.js
index 64861500a..fc67045a7 100644
--- a/test/resource_indicators/resource_indicators.test.js
+++ b/test/resource_indicators/resource_indicators.test.js
@@ -1,22 +1,23 @@
 /* eslint-disable prefer-destructuring */
 
+const { strict: assert } = require('assert');
+
 const sinon = require('sinon');
 const { expect } = require('chai');
 
 const bootstrap = require('../test_helper');
 const { features: { resourceIndicators: defaults } } = require('../../lib/helpers/defaults')();
 
-const fail = () => { throw new Error('expected promise to be rejected'); };
-
 describe('features.resourceIndicators defaults', () => {
   it('defaultResource', async () => {
     expect(await defaults.defaultResource()).to.be.undefined;
     expect(await defaults.defaultResource(undefined, undefined, ['urn:example:rs'])).to.deep.equal(['urn:example:rs']);
   });
 
-  it('getResourceServerInfo', async () => defaults.getResourceServerInfo().then(fail, (err) => {
+  it('getResourceServerInfo', () => assert.rejects(defaults.getResourceServerInfo(), (err) => {
     expect(err.message).to.equal('invalid_target');
     expect(err.error_description).to.equal('resource indicator is missing, or unknown');
+    return true;
   }));
 });