diff --git a/tests/HmacSha1Test.php b/tests/HmacSha1Test.php
new file mode 100644
index 0000000..0c2ec35
--- /dev/null
+++ b/tests/HmacSha1Test.php
@@ -0,0 +1,79 @@
+<?php
+
+use Mockery as m;
+use GaryJones\OAuth\HmacSha1;
+
+class HmacSha1Test extends PHPUnit_Framework_TestCase
+{
+    public function tearDown()
+    {
+        m::close();
+    }
+
+    public function testSignatureName()
+    {
+        $hmacsha1 = $this->getSignatureMethod();
+        $this->assertEquals('HMAC-SHA1', $hmacsha1->getName());
+    }
+
+    public function testBuildSignatureWithoutToken()
+    {
+        // Create instance of class to test
+        $hmacsha1 = $this->getSignatureMethod();
+
+        // Get mock objects
+        $request = $this->getRequest();
+        $client = $this->getClient();
+
+        // Run method being tested
+        $signature = $hmacsha1->buildSignature($request, $client);
+
+        // Check results
+        $this->assertEquals('RaZU4UG/wwJ/E5Df2/pePmwaS1Q=', $signature);
+    }
+
+    public function testBuildSignatureWithToken()
+    {
+        // Create instance of class to test
+        $hmacsha1 = $this->getSignatureMethod();
+
+        // Get mock objects
+        $request = $this->getRequest();
+        $client = $this->getClient();
+        $token = $this->getToken();
+
+        // Run method being tested
+        $signature = $hmacsha1->buildSignature($request, $client, $token);
+
+        // Check results
+        $this->assertEquals('1P/rfHzjnxBcNzngW9BEuT01goM=', $signature);
+    }
+
+    private function getSignatureMethod()
+    {
+        return new HmacSha1;
+    }
+
+    private function getRequest()
+    {
+        return m::mock('GaryJones\OAuth\Request', function ($mock) {
+            $mock->shouldReceive('getSignatureBaseString')
+                ->withNoArgs()
+                ->andReturn('POST&http%3A%2F%2Fexample.com%2Ffoobar&oauth_signature_method%3DHMAC-SHA1')->once();
+        });
+    }
+
+    private function getClient()
+    {
+        return m::mock('GaryJones\OAuth\Client', function ($mock) {
+            $mock->shouldReceive('getSecret')->withNoArgs()->andReturn('secret')->once();
+        });
+    }
+
+    private function getToken()
+    {
+        return m::mock('GaryJones\OAuth\Token', function ($mock) {
+            $mock->shouldReceive('getSecret')->withNoArgs()->andReturn('token_secret');
+        });
+    }
+}
diff --git a/tests/PlainTextTest.php b/tests/PlainTextTest.php
new file mode 100644
index 0000000..e435b8b
--- /dev/null
+++ b/tests/PlainTextTest.php
@@ -0,0 +1,75 @@
+<?php
+
+use Mockery as m;
+use GaryJones\OAuth\PlainText;
+
+class PlainTextTest extends PHPUnit_Framework_TestCase
+{
+    public function tearDown()
+    {
+        m::close();
+    }
+
+    public function testSignatureName()
+    {
+        $plaintext = $this->getSignatureMethod();
+        $this->assertEquals('PLAINTEXT', $plaintext->getName());
+    }
+
+    public function testBuildSignatureWithoutToken()
+    {
+        // Create instance of class to test
+        $plaintext = $this->getSignatureMethod();
+
+        // Get mock objects
+        $request = $this->getRequest();
+        $client = $this->getClient();
+
+        // Run method being tested
+        $signature = $plaintext->buildSignature($request, $client);
+
+        // Check results
+        $this->assertEquals('secret&', $signature);
+    }
+
+    public function testBuildSignatureWithToken()
+    {
+        // Create instance of class to test
+        $plaintext = $this->getSignatureMethod();
+
+        // Get mock objects
+        $request = $this->getRequest();
+        $client = $this->getClient();
+        $token = $this->getToken();
+
+        // Run method being tested
+        $signature = $plaintext->buildSignature($request, $client, $token);
+
+        // Check results
+        $this->assertEquals('secret&token_secret', $signature);
+    }
+
+    private function getSignatureMethod()
+    {
+        return new PlainText;
+    }
+
+    private function getRequest()
+    {
+        return m::mock('GaryJones\OAuth\Request');
+    }
+
+    private function getClient()
+    {
+        return m::mock('GaryJones\OAuth\Client', function ($mock) {
+            $mock->shouldReceive('getSecret')->withNoArgs()->andReturn('secret')->once();
+        });
+    }
+
+    private function getToken()
+    {
+        return m::mock('GaryJones\OAuth\Token', function ($mock) {
+            $mock->shouldReceive('getSecret')->withNoArgs()->andReturn('token_secret');
+        });
+    }
+}
diff --git a/tests/RequestTest.php b/tests/RequestTest.php
new file mode 100644
index 0000000..6306ca7
--- /dev/null
+++ b/tests/RequestTest.php
@@ -0,0 +1,36 @@
+<?php
+
+use Mockery as m;
+use GaryJones\OAuth\Request;
+
+class RequestTest extends PHPUnit_Framework_TestCase
+{
+    public function tearDown()
+    {
+        m::close();
+    }
+
+    public function testHttpMethodCanBeNormalized()
+    {
+        $request = new Request('foo', 'bar');
+        $this->assertEquals('FOO', $request->getNormalizedHttpMethod());
+    }
+
+    public function testHttpUrlCanBeNormalized()
+    {
+        $request = new Request('foo', 'bar');
+        $this->assertEquals('http://bar', $request->getNormalizedHttpUrl());
+        $request = new Request('foo', 'example.com:80');
+        $this->assertEquals('http://example.com', $request->getNormalizedHttpUrl());
+        $request = new Request('foo', 'example.com:81');
+        $this->assertEquals('http://example.com:81', $request->getNormalizedHttpUrl());
+        $request = new Request('foo', 'https://example.com');
+        $this->assertEquals('https://example.com', $request->getNormalizedHttpUrl());
+        $request = new Request('foo', 'https://example.com:443');
+        $this->assertEquals('https://example.com', $request->getNormalizedHttpUrl());
+        $request = new Request('foo', 'http://example.com/foobar');
+        $this->assertEquals('http://example.com/foobar', $request->getNormalizedHttpUrl());
+        $request = new Request('foo', 'example.org:80/foobar');
+        $this->assertEquals('http://example.org/foobar', $request->getNormalizedHttpUrl());
+    }
+}