diff --git a/.idea/php.xml b/.idea/php.xml
index fe09da7..b20d972 100644
--- a/.idea/php.xml
+++ b/.idea/php.xml
@@ -20,6 +20,11 @@
   <component name="PhpStanOptionsConfiguration">
     <option name="transferred" value="true" />
   </component>
+  <component name="PhpUnit">
+    <phpunit_settings>
+      <PhpUnitSettings load_method="PHPUNIT_PHAR" custom_loader_path="" phpunit_phar_path="$USER_HOME$/phpunit.phar" />
+    </phpunit_settings>
+  </component>
   <component name="PsalmOptionsConfiguration">
     <option name="transferred" value="true" />
   </component>
diff --git a/tests/OptsLib/ParseTest.php b/tests/OptsLib/ParseTest.php
new file mode 100644
index 0000000..367ee22
--- /dev/null
+++ b/tests/OptsLib/ParseTest.php
@@ -0,0 +1,70 @@
+<?php
+
+namespace OptsLib;
+
+use PHPUnit\Framework\TestCase;
+
+class ParseTest extends TestCase
+{
+    /**
+     * Testing parseArgument method when input is a string type, also testing different flag pattern
+     */
+    public function testParseArgumentWithStringInput()
+    {
+        $input = '--flag1=value1 -f value2 unmatched_string';
+        $expected_result = [
+            'flag1' => 'value1',
+            'f' => 'value2',
+            'unmatched_string' => true,
+        ];
+
+        $this->assertEquals($expected_result, Parse::parseArgument($input));
+    }
+
+    /**
+     * Testing parseArgument method when input is an array type
+     */
+    public function testParseArgumentWithArrayInput()
+    {
+        // Array argument will be transformed into '--flag1 value1 "-"f" value2" unmatched_string' 
+        $input = ['--flag1', 'value1', '-', 'f', 'value2', 'unmatched_string'];
+        $expected_result = [
+            'flag1' => 'value1',
+            'unmatched_string' => true,
+            'f' => true,
+            'value2' => true
+        ];
+
+        $this->assertEquals($expected_result, Parse::parseArgument($input));
+    }
+
+    /**
+     * Testing parseArgument method when input contains escaped quotes in a string argument
+     */
+    public function testParseArgumentWithEscapedQuotes()
+    {
+        $input = "--flag1=\"value1 with some \\\"escaped quotes\\\"\" -f 'value2 with some \\'escaped quotes\\'' unmatched_string";
+        $expected_result = [
+            'flag1' => 'value1 with some "escaped quotes"',
+            'f' => 'value2 with some \'escaped quotes\'',
+            'unmatched_string' => true,
+        ];
+
+        $this->assertEquals($expected_result, Parse::parseArgument($input));
+    }
+
+    /**
+     * Testing parseArgument method only takes maximum number of arguments specified
+     */
+    public function testParseArgumentWithMaxArguments()
+    {
+        $input = '--flag1=value1 -f value2 unmatched_string1 unmatched_string2';
+        $expected_result = [
+            'flag1' => 'value1',
+            'f' => 'value2',
+            'unmatched_string1' => true
+        ];  // It should only parse maximum 3 arguments
+
+        $this->assertEquals($expected_result, Parse::parseArgument($input, 2));
+    }
+}
\ No newline at end of file