Tests: add a dedicated test for the class constructor

tests/ConstructorTest.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace PHP_Parallel_Lint\PhpConsoleHighlighter\Test;
+
+use PHP_Parallel_Lint\PhpConsoleColor\ConsoleColor;
+use PHP_Parallel_Lint\PhpConsoleHighlighter\Highlighter;
+
+/**
+ * @covers PHP_Parallel_Lint\PhpConsoleHighlighter\Highlighter::__construct
+ */
+class ConstructorTest extends HighlighterTestCase
+{
+    /**
+     * Test constructor, including integration with ConsoleColor.
+     */
+    public function testConstructor()
+    {
+        $color = new ConsoleColor();
+        // Ensure that at least one style is already set so all branches get tested.
+        $color->addTheme(Highlighter::TOKEN_DEFAULT, 'bg_light_red');
+
+        $highlighter = new Highlighter($color);
+        $themes      = $color->getThemes();
+
+        $this->assertNotEmpty($themes);
+        $this->assertCount(7, $themes);
+    }
+}