diff --git a/tests/ColorLinesTest.php b/tests/ColorLinesTest.php
new file mode 100644
index 0000000..bf89f53
--- /dev/null
+++ b/tests/ColorLinesTest.php
@@ -0,0 +1,118 @@
+<?php
+
+namespace PHP_Parallel_Lint\PhpConsoleHighlighter\Test;
+
+use PHP_Parallel_Lint\PhpConsoleColor\ConsoleColor;
+use PHP_Parallel_Lint\PhpConsoleHighlighter\Highlighter;
+use ReflectionMethod;
+
+/**
+ * @covers PHP_Parallel_Lint\PhpConsoleHighlighter\Highlighter::colorLines
+ */
+class ColorLinesTest extends HighlighterTestCase
+{
+    /** @var string */
+    private $input = array(
+        7 => array (
+            0 => array (
+                0 => 'token_keyword',
+                1 => 'function ',
+            ),
+            1 => array (
+                0 => 'token_default',
+                1 => 'bar',
+            ),
+            2 => array (
+                0 => 'token_keyword',
+                1 => '(',
+            ),
+            3 => array (
+                0 => 'token_default',
+                1 => '$param',
+            ),
+            4 => array (
+                0 => 'token_unknown',
+                1 => ') ',
+            ),
+            5 => array (
+                0 => 'token_keyword',
+                1 => '{}',
+            ),
+        ),
+    );
+
+    /**
+     * Test the (private) `colorlines()` method.
+     *
+     * @dataProvider dataColorLines
+     *
+     * @param array $input     Tokenized code lines.
+     * @param array $output    Expected function output.
+     * @param bool  $withTheme Whether or not the mock should act as if themes
+     *                         have been registered or not.
+     *
+     * @return array
+     */
+    public function testColorLines($input, $expected, $withTheme = true)
+    {
+        $method = new ReflectionMethod('PHP_Parallel_Lint\PhpConsoleHighlighter\Highlighter', 'colorLines');
+        $method->setAccessible(true);
+
+        $highlighter = new Highlighter($this->getConsoleColorMock($withTheme));
+        $output = $method->invoke($highlighter, $input);
+        $method->setAccessible(false);
+
+        $this->assertSame($expected, $output);
+    }
+
+    /**
+     * Data provider.
+     *
+     * @return array
+     */
+    public function dataColorLines()
+    {
+        return array(
+            'No lines' => array(
+                'input'    => array(),
+                'expected' => array(),
+            ),
+            'With theme' => array(
+                'input'     => $this->input,
+                'expected'  => array(
+                    7 => '<token_keyword>function </token_keyword><token_default>bar</token_default><token_keyword>(</token_keyword><token_default>$param</token_default><token_unknown>) </token_unknown><token_keyword>{}</token_keyword>',
+                ),
+                'withTheme' => true,
+            ),
+            'Without theme' => array(
+                'input'     => $this->input,
+                'expected'  => array(
+                    7 => 'function bar($param) {}',
+                ),
+                'withTheme' => false,
+            ),
+        );
+    }
+
+    /**
+     * Integration test for the colorLines() method.
+     */
+    public function testColorLinesWithRealColors()
+    {
+        $expected = array(
+            7 => "\033[32mfunction \033[0m\033[39mbar\033[0m\033[32m(\033[0m\033[39m\$param\033[0m) \033[32m{}\033[0m",
+        );
+
+        $color = new ConsoleColor();
+        $color->setForceStyle(true);
+
+        $method = new ReflectionMethod('PHP_Parallel_Lint\PhpConsoleHighlighter\Highlighter', 'colorLines');
+        $method->setAccessible(true);
+
+        $highlighter = new Highlighter($color);
+        $output = $method->invoke($highlighter, $this->input);
+        $method->setAccessible(false);
+
+        $this->assertSame($expected, $output);
+    }
+}