diff --git a/src/Majora/Component/OAuth/Tests/GrantType/PasswordGrantExtensionTest.php b/src/Majora/Component/OAuth/Tests/GrantType/PasswordGrantExtensionTest.php
new file mode 100644
index 0000000..0b9c5ae
--- /dev/null
+++ b/src/Majora/Component/OAuth/Tests/GrantType/PasswordGrantExtensionTest.php
@@ -0,0 +1,156 @@
+<?php
+namespace Majora\Component\OAuth\Tests\GrantType;
+
+use Majora\Component\OAuth\Entity\LoginAttempt;
+use Majora\Component\OAuth\Exception\InvalidGrantException;
+use Majora\Component\OAuth\GrantType\PasswordGrantExtension;
+use Majora\Component\OAuth\Loader\AccountLoaderInterface;
+use Majora\Component\OAuth\Model\AccountInterface;
+use Majora\Component\OAuth\Model\ApplicationInterface;
+use Prophecy\Argument;
+use Symfony\Component\OptionsResolver\OptionsResolver;
+use Symfony\Component\Security\Core\Encoder\UserPasswordEncoderInterface;
+use Symfony\Component\Security\Core\User\UserInterface;
+
+/**
+ * Unit test class for Majora\Component\OAuth\GrantType\PasswordGrantTypeExtension.
+ */
+class PasswordGrantExtensionTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * Test configureRequestParameters() method.
+     */
+    public function testConfigureRequestParameters()
+    {
+        $optionsResolver = new OptionsResolver();
+        $passwordGrantExtension = new PasswordGrantExtension(
+            $this->prophesize(AccountLoaderInterface::class)->reveal(),
+            $this->prophesize(UserPasswordEncoderInterface::class)->reveal()
+        );
+        $passwordGrantExtension->configureRequestParameters($optionsResolver);
+
+        // Testing the required options
+        $actualRequiredOptions = $optionsResolver->getRequiredOptions();
+        $expectedRequiredOptions = ['password', 'username'];
+        $this->assertEquals($expectedRequiredOptions, $actualRequiredOptions, '', $delta = 0.0, 10, true); // Not caring about keys
+
+        // Testing the optional options
+        $actualOptionalOptions = array_diff($optionsResolver->getDefinedOptions(), $actualRequiredOptions);
+        $expectedOptionalOptions = [];
+        $this->assertCount(0, array_diff($expectedOptionalOptions, $actualOptionalOptions));
+    }
+
+    /**
+     * Test grant() method on success
+     */
+    public function testSuccessGrant()
+    {
+        // Mocking AccountInterface
+        $account = $this->prophesize(AccountInterface::class)->reveal();
+
+        // Mocking AccountLoader
+        $accountLoader = $this->prophesize(AccountLoaderInterface::class);
+        $accountLoader->retrieveOnApplicationByUsername(Argument::type(ApplicationInterface::class), 'username_test')
+            ->willReturn($account)
+            ->shouldBeCalled();
+
+        // Mocking UserPasswordEncoderInterface
+        $userPasswordEncoder = $this->prophesize(UserPasswordEncoderInterface::class);
+        $userPasswordEncoder->isPasswordValid(Argument::type(UserInterface::class), 'password_test')
+            ->willReturn(true)
+            ->shouldBeCalled();
+
+        $passwordGrantExtension = new PasswordGrantExtension(
+            $accountLoader->reveal(),
+            $userPasswordEncoder->reveal()
+        );
+
+        // Mocking LoginAttempt
+        $loginAttempt = $this->prophesize(LoginAttempt::class);
+        $loginAttempt->getData('username')
+            ->willReturn('username_test')
+            ->shouldBeCalled();
+        $loginAttempt->getData('password')
+            ->willReturn('password_test')
+            ->shouldBeCalled();
+
+        $actualAccount = $passwordGrantExtension->grant(
+            $this->prophesize(ApplicationInterface::class)->reveal(),
+            $loginAttempt->reveal()
+        );
+
+        $this->assertSame($account, $actualAccount);
+    }
+
+    /**
+     * Test grant() when it fails loading an account.
+     */
+    public function testGrantFailingAccountLoading()
+    {
+        // Mocking AccountLoader
+        $accountLoader = $this->prophesize(AccountLoaderInterface::class);
+        $accountLoader->retrieveOnApplicationByUsername(Argument::type(ApplicationInterface::class), 'username_test')
+            ->willReturn(null)
+            ->shouldBeCalled();
+
+        $passwordGrantExtension = new PasswordGrantExtension(
+            $accountLoader->reveal(),
+            $this->prophesize(UserPasswordEncoderInterface::class)->reveal()
+        );
+
+        // Mocking LoginAttempt
+        $loginAttempt = $this->prophesize(LoginAttempt::class);
+        $loginAttempt->getData('username')
+            ->willReturn('username_test')
+            ->shouldBeCalled();
+
+        $this->expectException(InvalidGrantException::class);
+        $this->expectExceptionMessage('Username not found on loaded application.');
+
+        $passwordGrantExtension->grant(
+            $this->prophesize(ApplicationInterface::class)->reveal(),
+            $loginAttempt->reveal()
+        );
+    }
+
+    /**
+     * Test grant() when it fails to validate the password.
+     */
+    public function testGrantFailingPasswordValidation()
+    {
+        // Mocking AccountLoader
+        $accountLoader = $this->prophesize(AccountLoaderInterface::class);
+        $accountLoader->retrieveOnApplicationByUsername(Argument::type(ApplicationInterface::class), 'username_test')
+            ->willReturn($this->prophesize(AccountInterface::class)->reveal())
+            ->shouldBeCalled();
+
+        // Mocking UserPasswordEncoderInterface
+        $userPasswordEncoder = $this->prophesize(UserPasswordEncoderInterface::class);
+        $userPasswordEncoder->isPasswordValid(Argument::type(UserInterface::class), 'password_test')
+            ->willReturn(false)
+            ->shouldBeCalled();
+
+        $passwordGrantExtension = new PasswordGrantExtension(
+            $accountLoader->reveal(),
+            $userPasswordEncoder->reveal()
+        );
+
+        // Mocking LoginAttempt
+        $loginAttempt = $this->prophesize(LoginAttempt::class);
+        $loginAttempt->getData('username')
+            ->willReturn('username_test')
+            ->shouldBeCalled();
+        $loginAttempt->getData('password')
+            ->willReturn('password_test')
+            ->shouldBeCalled();
+
+
+        $this->expectException(InvalidGrantException::class);
+        $this->expectExceptionMessage('Invalid password for loaded account.');
+
+        $passwordGrantExtension->grant(
+            $this->prophesize(ApplicationInterface::class)->reveal(),
+            $loginAttempt->reveal()
+        );
+    }
+}