diff --git a/tests/Comment/CommentTest.php b/tests/Comment/CommentTest.php
index d80c65f98..7befcc271 100644
--- a/tests/Comment/CommentTest.php
+++ b/tests/Comment/CommentTest.php
@@ -20,7 +20,7 @@ final class CommentTest extends TestCase
      */
     public function keepCommentsInOutput(): void
     {
-        $oCss = TestsParserTest::parsedStructureForFile('comments');
+        $cssDocument = TestsParserTest::parsedStructureForFile('comments');
         self::assertSame('/** Number 11 **/
 
 /**
@@ -45,7 +45,7 @@ public function keepCommentsInOutput(): void
 		position: absolute;
 	}
 }
-', $oCss->render(OutputFormat::createPretty()));
+', $cssDocument->render(OutputFormat::createPretty()));
         self::assertSame(
             '/** Number 11 **//**' . "\n"
             . ' * Comments' . "\n"
@@ -53,7 +53,7 @@ public function keepCommentsInOutput(): void
             . '/* Number 4 *//* Number 5 */.foo,#bar{'
             . '/* Number 6 */background-color:#000;}@media screen{'
             . '/** Number 10 **/#foo.bar{/** Number 10b **/position:absolute;}}',
-            $oCss->render(OutputFormat::createCompact()->setRenderComments(true))
+            $cssDocument->render(OutputFormat::createCompact()->setRenderComments(true))
         );
     }
 
diff --git a/tests/ParserTest.php b/tests/ParserTest.php
index a5541de7a..47ec1ffaf 100644
--- a/tests/ParserTest.php
+++ b/tests/ParserTest.php
@@ -161,8 +161,8 @@ public function colorParsing(): void
                 self::assertEmpty($colorRules);
             }
         }
-        foreach ($document->getAllValues('color') as $sColor) {
-            self::assertSame('red', $sColor);
+        foreach ($document->getAllValues('color') as $colorValue) {
+            self::assertSame('red', $colorValue);
         }
         self::assertSame(
             '#mine {color: red;border-color: #0a64e6;border-color: rgba(10,100,231,.3);outline-color: #222;'
@@ -463,9 +463,9 @@ public function functionSyntax(): void
             . '.collapser.expanded + * {height: auto;}';
         self::assertSame($expected, $document->render());
 
-        foreach ($document->getAllValues(null, true) as $mValue) {
-            if ($mValue instanceof Size && $mValue->isSize()) {
-                $mValue->setSize($mValue->getSize() * 3);
+        foreach ($document->getAllValues(null, true) as $value) {
+            if ($value instanceof Size && $value->isSize()) {
+                $value->setSize($value->getSize() * 3);
             }
         }
         $expected = \str_replace(['1.2em', '.2em', '60%'], ['3.6em', '.6em', '180%'], $expected);
@@ -952,12 +952,12 @@ public function missingPropertyValueLenient(): void
      * Parses structure for file.
      *
      * @param string $filename
-     * @param Settings|null $oSettings
+     * @param Settings|null $settings
      */
-    public static function parsedStructureForFile($filename, $oSettings = null): Document
+    public static function parsedStructureForFile($filename, $settings = null): Document
     {
         $filename = __DIR__ . "/fixtures/$filename.css";
-        $parser = new Parser(\file_get_contents($filename), $oSettings);
+        $parser = new Parser(\file_get_contents($filename), $settings);
         return $parser->parse();
     }
 
@@ -1011,8 +1011,8 @@ public function lineNumbersParsing(): void
         self::assertSame(27, $rules[1]->getLineNo());
 
         $actualColorLineNumbers = [];
-        foreach ($valueOfSecondRule->getColor() as $oSize) {
-            $actualColorLineNumbers[] = $oSize->getLineNo();
+        foreach ($valueOfSecondRule->getColor() as $size) {
+            $actualColorLineNumbers[] = $size->getLineNo();
         }
 
         self::assertSame($expectedColorLineNumbers, $actualColorLineNumbers);
@@ -1044,16 +1044,16 @@ public function unexpectedTokenExceptionLineNo(): void
     public function commentExtracting(): void
     {
         $document = self::parsedStructureForFile('comments');
-        $aNodes = $document->getContents();
+        $nodes = $document->getContents();
 
         // Import property.
-        $importComments = $aNodes[0]->getComments();
+        $importComments = $nodes[0]->getComments();
         self::assertCount(2, $importComments);
         self::assertSame("*\n * Comments\n ", $importComments[0]->getComment());
         self::assertSame(' Hell ', $importComments[1]->getComment());
 
         // Declaration block.
-        $fooBarBlock = $aNodes[1];
+        $fooBarBlock = $nodes[1];
         $fooBarBlockComments = $fooBarBlock->getComments();
         // TODO Support comments in selectors.
         // $this->assertCount(2, $fooBarBlockComments);
@@ -1068,11 +1068,11 @@ public function commentExtracting(): void
         self::assertSame(' Number 6 ', $fooBarRuleComments[0]->getComment());
 
         // Media property.
-        $mediaComments = $aNodes[2]->getComments();
+        $mediaComments = $nodes[2]->getComments();
         self::assertCount(0, $mediaComments);
 
         // Media children.
-        $mediaRules = $aNodes[2]->getContents();
+        $mediaRules = $nodes[2]->getContents();
         $fooBarComments = $mediaRules[0]->getComments();
         self::assertCount(1, $fooBarComments);
         self::assertSame('* Number 10 *', $fooBarComments[0]->getComment());
diff --git a/tests/RuleSet/DeclarationBlockTest.php b/tests/RuleSet/DeclarationBlockTest.php
index 2de33b96c..2f5dc9f22 100644
--- a/tests/RuleSet/DeclarationBlockTest.php
+++ b/tests/RuleSet/DeclarationBlockTest.php
@@ -21,8 +21,8 @@ final class DeclarationBlockTest extends TestCase
      */
     public function overrideRules(): void
     {
-        $sCss = '.wrapper { left: 10px; text-align: left; }';
-        $parser = new Parser($sCss);
+        $css = '.wrapper { left: 10px; text-align: left; }';
+        $parser = new Parser($css);
         $document = $parser->parse();
         $rule = new Rule('right');
         $rule->setValue('-10px');
@@ -43,8 +43,8 @@ public function overrideRules(): void
      */
     public function ruleInsertion(): void
     {
-        $sCss = '.wrapper { left: 10px; text-align: left; }';
-        $parser = new Parser($sCss);
+        $css = '.wrapper { left: 10px; text-align: left; }';
+        $parser = new Parser($css);
         $document = $parser->parse();
         $contents = $document->getContents();
         $wrapper = $contents[0];