diff --git a/package.json b/package.json
index 66541144..39097226 100644
--- a/package.json
+++ b/package.json
@@ -29,7 +29,7 @@
     "branches": 95,
     "check-coverage": true,
     "exclude": [
-      "src/test/**/*.spec.ts",
+      "src/SMTP.ts",
       "src/cli.ts"
     ],
     "extension": [
diff --git a/test/Common.spec.ts b/test/Common.spec.ts
index 7e757854..a3d2697c 100644
--- a/test/Common.spec.ts
+++ b/test/Common.spec.ts
@@ -14,11 +14,15 @@
  */
 import {expect} from 'chai';
 import {slow, suite, test, timeout} from 'mocha-typescript';
-import {deleteUndefinedProperties} from '../src/common';
+import {
+  deleteUndefinedProperties,
+  isNodeEnvironment,
+  isProductiveEnvironment,
+  isProductiveNodeEnvironment,
+} from '../src/common';
 
 @suite(timeout(2000), slow(1000))
 export class CommonSpec {
-  /* tslint:disable:member-ordering */
   @test
   deleteUndefinedProperties1() {
     expect(deleteUndefinedProperties(
@@ -67,4 +71,48 @@ export class CommonSpec {
       },
     );
   }
+
+  @test
+  isNodeEnvironment() {
+    expect(isNodeEnvironment()).to.be.equal(true);
+
+    const savedProcess = process;
+
+    // @ts-ignore
+    process = undefined;
+
+    expect(isNodeEnvironment()).to.be.equal(false);
+
+    process = savedProcess;
+  }
+
+  @test
+  isProductiveEnvironment() {
+    const nodeEnv = process.env.NODE_ENV;
+
+    process.env.NODE_ENV = '';
+
+    expect(isProductiveEnvironment()).to.be.equal(false);
+
+    process.env.NODE_ENV = 'production';
+
+    expect(isProductiveEnvironment()).to.be.equal(true);
+
+    process.env.NODE_ENV = nodeEnv;
+  }
+
+  @test
+  isProductiveNodeEnvironment() {
+    const nodeEnv = process.env.NODE_ENV;
+
+    process.env.NODE_ENV = '';
+
+    expect(isProductiveNodeEnvironment()).to.be.equal(false);
+
+    process.env.NODE_ENV = 'production';
+
+    expect(isProductiveNodeEnvironment()).to.be.equal(true);
+
+    process.env.NODE_ENV = nodeEnv;
+  }
 }
diff --git a/test/Logger.spec.ts b/test/Logger.spec.ts
index 77812d49..68c657c0 100644
--- a/test/Logger.spec.ts
+++ b/test/Logger.spec.ts
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2018 StApps
+ * Copyright (C) 2018, 2019 StApps
  * This program is free software: you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the Free
  * Software Foundation, version 3.
@@ -12,216 +12,282 @@
  * You should have received a copy of the GNU General Public License along with
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
+import * as chai from 'chai';
 import {expect} from 'chai';
+import * as chaiAsPromised from 'chai-as-promised';
 import {slow, suite, test, timeout} from 'mocha-typescript';
 import * as sinon from 'sinon';
 import {Logger} from '../src/Logger';
+import {DummyTransport} from './Transport.spec';
 
-const logger1 = new Logger();
+chai.should();
+chai.use(chaiAsPromised);
 
 @suite(timeout(2000), slow(1000))
 export class LoggerSpec {
-
   @test
-  error1(done: () => void) {
-    let
-      stub;
-    stub = sinon.stub(console, 'error');
+  async error() {
+    const stub = sinon.stub(console, 'error');
 
-    logger1.error('Foobar');
+    await Logger.error('Foobar');
 
     stub.restore();
 
-    expect(stub.args[0][0]).contains('[ERROR] Foobar');
-
-    done();
+    expect(stub.args[0][0]).contains('[ERROR]');
+    expect(stub.args[0][0]).contains('Foobar');
   }
 
   @test
-  error2(done: () => void) {
+  async errorInProductiveEnvironment() {
+    const errorStub = sinon.stub(console, 'error');
+
+    const nodeEnv = process.env.NODE_ENV;
+    process.env.NODE_ENV = 'production';
+
+    await Logger.error('Foobar').should.be.rejectedWith(Error);
+    expect(errorStub.callCount).to.be.equal(1);
+
+    process.env.ALLOW_NO_TRANSPORT = 'true';
+
+    await Logger.error('Foobar').should.not.be.rejectedWith(Error);
+    expect(errorStub.callCount).to.be.equal(2);
+
+    delete process.env.ALLOW_NO_TRANSPORT;
+
+    Logger.setTransport(new DummyTransport());
+
+    await Logger.error('Foobar').should.not.be.rejectedWith(Error);
+    expect(errorStub.callCount).to.be.equal(3);
+
+    Logger.setTransport();
+
+    process.env.NODE_ENV = nodeEnv;
+
+    errorStub.restore();
+  }
+
+  @test
+  async errorNoOutput() {
+    const stub = sinon.stub(console, 'error');
+
+    process.env.STAPPS_LOG_LEVEL = '0';
+
+    await Logger.error('Foobar');
+
+    stub.restore();
+
+    delete process.env.STAPPS_LOG_LEVEL;
+
+    return expect(stub.called).to.be.false;
+  }
+
+  @test
+  async errorWithError() {
     const e = new Error();
     const stub = sinon.stub(console, 'error');
 
-    logger1.error(e);
+    await Logger.error(e);
 
     stub.restore();
 
     expect(stub.args[0][0]).contains('Error').contains('at').contains(process.cwd());
-
-    done();
   }
 
   @test
-  info(done: () => void) {
-    let
-      stub;
-    stub = sinon.stub(console, 'info');
+  getLogLevel() {
+    const savedProcess = process;
 
-    logger1.info('Foobar');
+    // @ts-ignore
+    process = undefined;
+
+    (global as any).window = {
+      STAPPS_LOG_LEVEL: 0,
+    };
+
+    const stub = sinon.stub(console, 'info');
+
+    Logger.info('Foobar');
 
     stub.restore();
 
-    expect(stub.args[0][0]).contains('[INFO] Foobar');
+    process = savedProcess;
 
-    done();
+    delete (global as any).window;
+
+    return expect(stub.called).to.be.false;
   }
 
   @test
-  log(done: () => void) {
-    let
-      stub;
-    stub = sinon.stub(console, 'log');
+  info() {
+    const stub = sinon.stub(console, 'info');
 
-    logger1.log('Foobar');
+    Logger.info('Foobar');
 
     stub.restore();
 
-    expect(stub.args[0][0]).contains('[LOG] Foobar');
-
-    done();
+    expect(stub.args[0][0]).contains('[INFO]');
+    expect(stub.args[0][0]).contains('Foobar');
   }
 
   @test
-  logLevel1(done: () => void) {
-    let logStub;
-    let warnStub;
+  infoNoOutput() {
+    const stub = sinon.stub(console, 'info');
 
-    process.env.STAPPS_LOG_LEVEL = '8';
+    process.env.STAPPS_LOG_LEVEL = '0';
 
-    logStub = sinon.stub(console, 'log');
-    warnStub = sinon.stub(console, 'warn');
+    Logger.info('Foobar');
 
-    logger1.ok('foo');
-    logger1.warn('bar');
-
-    logStub.restore();
-
-    /* tslint:disable:no-unused-expression */
-    expect(logStub.called).to.be.false;
-    expect(warnStub.called).to.be.false;
-    /* tslint:enable */
+    stub.restore();
 
     delete process.env.STAPPS_LOG_LEVEL;
 
-    logger1.warn('bar');
-
-    /* tslint:disable:no-unused-expression */
-    expect(warnStub.called).to.be.true;
-    /* tslint:enable */
-
-    warnStub.restore();
-
-    done();
+    return expect(stub.called).to.be.false;
   }
 
   @test
-  logLevel2(done: () => void) {
-    let logStub;
-    let warnStub;
+  initialized() {
+    Logger.setTransport(new DummyTransport());
 
-    process.env.STAPPS_LOG_LEVEL = '12';
+    expect(() => {
+      Logger.initialized();
+    }).not.to.throw();
 
-    logStub = sinon.stub(console, 'log');
-    warnStub = sinon.stub(console, 'warn');
+    Logger.setTransport();
+  }
 
-    logger1.ok('foo');
-    logger1.warn('bar');
+  @test
+  initializedInProductiveEnvironment() {
+    const nodeEnv = process.env.NODE_ENV;
+    process.env.NODE_ENV = 'production';
 
-    logStub.restore();
+    Logger.setTransport(new DummyTransport());
 
-    /* tslint:disable:no-unused-expression */
-    expect(logStub.called).to.be.false;
-    expect(warnStub.called).to.be.true;
-    /* tslint:enable */
+    expect(() => {
+      Logger.initialized();
+    }).not.to.throw();
+
+    Logger.setTransport();
+
+    expect(() => {
+      Logger.initialized();
+    }).to.throw();
+
+    const stub = sinon.stub(console, 'warn');
+
+    process.env.ALLOW_NO_TRANSPORT = 'true';
+
+    expect(() => {
+      Logger.initialized();
+    }).not.to.throw();
+
+    delete process.env.ALLOW_NO_TRANSPORT;
+
+    expect(stub.called).to.be.equal(true);
+
+    stub.restore();
+
+    process.env.NODE_ENV = nodeEnv;
+  }
+
+  @test
+  log() {
+    const stub = sinon.stub(console, 'log');
+
+    Logger.log('Foobar');
+
+    stub.restore();
+
+    expect(stub.args[0][0]).contains('[LOG]');
+    expect(stub.args[0][0]).contains('Foobar');
+  }
+
+  @test
+  logNoOutput() {
+    const stub = sinon.stub(console, 'log');
+
+    process.env.STAPPS_LOG_LEVEL = '0';
+
+    Logger.log('Foobar');
+
+    stub.restore();
 
     delete process.env.STAPPS_LOG_LEVEL;
 
-    logger1.warn('bar');
-
-    /* tslint:disable:no-unused-expression */
-    expect(warnStub.called).to.be.true;
-    /* tslint:enable */
-
-    warnStub.restore();
-
-    done();
+    return expect(stub.called).to.be.false;
   }
 
   @test
-  logLevel3(done: () => void) {
-    let logStub;
-    let warnStub;
+  ok() {
+    const stub = sinon.stub(console, 'log');
 
-    process.env.STAPPS_LOG_LEVEL = '20';
+    Logger.ok('Foobar');
 
-    logStub = sinon.stub(console, 'log');
-    warnStub = sinon.stub(console, 'warn');
+    stub.restore();
 
-    logger1.ok('foo');
-    logger1.warn('bar');
+    expect(stub.args[0][0]).contains('[OK]');
+    expect(stub.args[0][0]).contains('Foobar');
+  }
 
-    logStub.restore();
+  @test
+  okNoOutput() {
+    const stub = sinon.stub(console, 'log');
 
-    /* tslint:disable:no-unused-expression */
-    expect(logStub.called).to.be.true;
-    expect(warnStub.called).to.be.true;
-    /* tslint:enable */
+    process.env.STAPPS_LOG_LEVEL = '0';
+
+    Logger.ok('Foobar');
+
+    stub.restore();
 
     delete process.env.STAPPS_LOG_LEVEL;
 
-    logger1.warn('bar');
-
-    /* tslint:disable:no-unused-expression */
-    expect(warnStub.called).to.be.true;
-    /* tslint:enable */
-
-    warnStub.restore();
-
-    done();
+    return expect(stub.called).to.be.false;
   }
 
   @test
-  ok(done: () => void) {
-    let
-      stub;
-    stub = sinon.stub(console, 'log');
-
-    logger1.ok('Foobar');
-
-    stub.restore();
-
-    expect(stub.args[0][0]).contains('[OK] Foobar');
-
-    done();
+  setTransport() {
+    expect(() => {
+      Logger.setTransport(new DummyTransport());
+      Logger.setTransport();
+    }).not.to.throw();
   }
 
   @test
-  stringifyArguments(done: () => void) {
-    let
-      stub;
-    stub = sinon.stub(console, 'log');
+  stringifyArguments() {
+    const stub = sinon.stub(console, 'log');
 
-    logger1.log('foo', 'bar');
+    Logger.log('foo', 'bar');
 
     stub.restore();
 
-    expect(stub.args[0][0]).contains('[LOG]').and.contains('foo').and.contains('bar');
-
-    done();
+    expect(stub.args[0][0]).contains('[LOG]');
+    expect(stub.args[0][0]).contains('foo');
+    expect(stub.args[0][0]).contains('bar');
   }
 
   @test
-  warn(done: () => void) {
-    let
-      stub;
-    stub = sinon.stub(console, 'warn');
+  warn() {
+    const stub = sinon.stub(console, 'warn');
 
-    logger1.warn('Foobar');
+    Logger.warn('Foobar');
 
     stub.restore();
 
-    expect(stub.args[0][0]).contains('[WARN] Foobar');
+    expect(stub.args[0][0]).contains('[WARN]');
+    expect(stub.args[0][0]).contains('Foobar');
+  }
 
-    done();
+  @test
+  warnNoOutput() {
+    const stub = sinon.stub(console, 'warn');
+
+    process.env.STAPPS_LOG_LEVEL = '0';
+
+    Logger.warn('Foobar');
+
+    stub.restore();
+
+    delete process.env.STAPPS_LOG_LEVEL;
+
+    return expect(stub.called).to.be.false;
   }
 }
diff --git a/test/Transport.spec.ts b/test/Transport.spec.ts
new file mode 100644
index 00000000..5d5500ec
--- /dev/null
+++ b/test/Transport.spec.ts
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2019 StApps
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+import {expect} from 'chai';
+import {slow, suite, test, timeout} from 'mocha-typescript';
+import {isTransportWithVerification} from '../src/common';
+import {Transport, VerifiableTransport} from '../src/Transport';
+
+export class DummyTransport extends Transport {
+  send(subject: string, message: string): Promise<string> {
+    return new Promise((resolve, reject) => {
+      if (0 === 0) {
+        resolve(subject);
+      }
+
+      reject(message);
+    });
+  }
+}
+
+export class VerifiableDummyTransport extends VerifiableTransport {
+  isVerified(): boolean {
+    return false;
+  }
+
+  send(subject: string, message: string): Promise<string> {
+    return new Promise((resolve, reject) => {
+      if (0 === 0) {
+        resolve(subject);
+      }
+
+      reject(message);
+    });
+  }
+
+  verify(): Promise<boolean> {
+    return new Promise((resolve) => {
+      resolve(true);
+    });
+  }
+}
+
+@suite(timeout(2000), slow(1000))
+export class TransportSpec {
+  @test
+  isNotTransportWithVerification() {
+    return expect(isTransportWithVerification(new DummyTransport())).to.be.false;
+  }
+
+  @test
+  isTransportWithVerification() {
+    return expect(isTransportWithVerification(new VerifiableDummyTransport())).to.be.true;
+  }
+}