Fixed case in test filenames

tests/Key/JWTPlaintextKeyTest.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace NoccyLabs\SimpleJWT\Key;
+
+
+class JWTPlaintextKeyTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @covers \NoccyLabs\SimpleJWT\Key\JWTPlaintextKey
+     */
+    public function testThePlaintextKeyShouldBeReturned()
+    {
+        $key = new JWTPlaintextKey("foo");
+        $this->assertEquals("foo", $key->getBinaryKey());
+
+        $key = new JWTPlaintextKey("bar");
+        $this->assertEquals("bar", $key->getBinaryKey());
+    }
+}