diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index ec6e8e3b28..e157c03ac5 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -11,6 +11,60 @@
 		</properties>
 	</rule>
 
+	<rule ref="WordPress.NamingConventions.ValidVariableName">
+		<properties>
+			<property name="customPropertiesWhitelist" type="array">
+				<!-- From database structure queries -->
+				<element value="Collation"/>
+				<element value="Column_name"/>
+				<element value="Default"/>
+				<element value="Extra"/>
+				<element value="Field"/>
+				<element value="Index_type"/>
+				<element value="Key"/>
+				<element value="Key_name"/>
+				<element value="Msg_text"/>
+				<element value="Non_unique"/>
+				<element value="Null"/>
+				<element value="Sub_part"/>
+				<element value="Type"/>
+				<!-- From plugin/theme data -->
+				<element value="authorAndUri"/>
+				<element value="Name"/>
+				<element value="Version"/>
+				<!-- From the result of wp_xmlrpc_server::wp_getPageList() -->
+				<element value="dateCreated"/>
+
+				<!-- From DOMDocument -->
+				<element value="childNodes"/>
+				<element value="formatOutput"/>
+				<element value="nodeName"/>
+				<element value="nodeType"/>
+				<element value="parentNode"/>
+				<element value="preserveWhiteSpace"/>
+				<element value="textContent"/>
+				<!-- From PHPMailer -->
+				<element value="AltBody"/>
+				<element value="Body"/>
+				<element value="CharSet"/>
+				<element value="ContentType"/>
+				<element value="Encoding"/>
+				<element value="Hostname"/>
+				<element value="mailHeader"/>
+				<element value="MIMEBody"/>
+				<element value="MIMEHeader"/>
+				<element value="Sender"/>
+				<element value="Subject"/>
+				<!-- From PHPUnit_Util_Getopt -->
+				<element value="longOptions"/>
+				<!-- From POP3 -->
+				<element value="ERROR"/>
+				<!-- From ZipArchive -->
+				<element value="numFiles"/>
+			</property>
+		</properties>
+	</rule>
+
 	<arg name="extensions" value="php"/>
 
 	<!-- Strip the filepaths down to the relevant bit. -->
diff --git a/src/wp-includes/class-wp-comment-query.php b/src/wp-includes/class-wp-comment-query.php
index 95ab3a6b35..dbf005c8fa 100644
--- a/src/wp-includes/class-wp-comment-query.php
+++ b/src/wp-includes/class-wp-comment-query.php
@@ -555,7 +555,7 @@ class WP_Comment_Query {
 				preg_split( '/[,\s]/', $this->query_vars['orderby'] );
 
 			$orderby_array            = array();
-			$found_orderby_comment_ID = false;
+			$found_orderby_comment_id = false;
 			foreach ( $ordersby as $_key => $_value ) {
 				if ( ! $_value ) {
 					continue;
@@ -569,8 +569,8 @@ class WP_Comment_Query {
 					$_order   = $_value;
 				}
 
-				if ( ! $found_orderby_comment_ID && in_array( $_orderby, array( 'comment_ID', 'comment__in' ) ) ) {
-					$found_orderby_comment_ID = true;
+				if ( ! $found_orderby_comment_id && in_array( $_orderby, array( 'comment_ID', 'comment__in' ) ) ) {
+					$found_orderby_comment_id = true;
 				}
 
 				$parsed = $this->parse_orderby( $_orderby );
@@ -593,24 +593,24 @@ class WP_Comment_Query {
 			}
 
 			// To ensure determinate sorting, always include a comment_ID clause.
-			if ( ! $found_orderby_comment_ID ) {
-				$comment_ID_order = '';
+			if ( ! $found_orderby_comment_id ) {
+				$comment_id_order = '';
 
 				// Inherit order from comment_date or comment_date_gmt, if available.
 				foreach ( $orderby_array as $orderby_clause ) {
 					if ( preg_match( '/comment_date(?:_gmt)*\ (ASC|DESC)/', $orderby_clause, $match ) ) {
-						$comment_ID_order = $match[1];
+						$comment_id_order = $match[1];
 						break;
 					}
 				}
 
 				// If no date-related order is available, use the date from the first available clause.
-				if ( ! $comment_ID_order ) {
+				if ( ! $comment_id_order ) {
 					foreach ( $orderby_array as $orderby_clause ) {
 						if ( false !== strpos( 'ASC', $orderby_clause ) ) {
-							$comment_ID_order = 'ASC';
+							$comment_id_order = 'ASC';
 						} else {
-							$comment_ID_order = 'DESC';
+							$comment_id_order = 'DESC';
 						}
 
 						break;
@@ -618,11 +618,11 @@ class WP_Comment_Query {
 				}
 
 				// Default to DESC.
-				if ( ! $comment_ID_order ) {
-					$comment_ID_order = 'DESC';
+				if ( ! $comment_id_order ) {
+					$comment_id_order = 'DESC';
 				}
 
-				$orderby_array[] = "$wpdb->comments.comment_ID $comment_ID_order";
+				$orderby_array[] = "$wpdb->comments.comment_ID $comment_id_order";
 			}
 
 			$orderby = implode( ', ', $orderby_array );
diff --git a/tests/phpunit/tests/avatar.php b/tests/phpunit/tests/avatar.php
index 3722f6ec1f..898c30f296 100644
--- a/tests/phpunit/tests/avatar.php
+++ b/tests/phpunit/tests/avatar.php
@@ -103,21 +103,21 @@ class Tests_Avatar extends WP_UnitTestCase {
 		$this->assertEquals( $url, $url2 );
 	}
 
-	protected $fakeURL;
+	protected $fake_url;
 	/**
 	 * @ticket 21195
 	 */
 	public function test_pre_get_avatar_url_filter() {
-		$this->fakeURL = 'haha wat';
+		$this->fake_url = 'haha wat';
 
 		add_filter( 'pre_get_avatar_data', array( $this, 'pre_get_avatar_url_filter' ), 10, 1 );
 		$url = get_avatar_url( 1 );
 		remove_filter( 'pre_get_avatar_data', array( $this, 'pre_get_avatar_url_filter' ), 10 );
 
-		$this->assertEquals( $url, $this->fakeURL );
+		$this->assertEquals( $url, $this->fake_url );
 	}
 	public function pre_get_avatar_url_filter( $args ) {
-		$args['url'] = $this->fakeURL;
+		$args['url'] = $this->fake_url;
 		return $args;
 	}
 
@@ -125,16 +125,16 @@ class Tests_Avatar extends WP_UnitTestCase {
 	 * @ticket 21195
 	 */
 	public function test_get_avatar_url_filter() {
-		$this->fakeURL = 'omg lol';
+		$this->fake_url = 'omg lol';
 
 		add_filter( 'get_avatar_url', array( $this, 'get_avatar_url_filter' ), 10, 1 );
 		$url = get_avatar_url( 1 );
 		remove_filter( 'get_avatar_url', array( $this, 'get_avatar_url_filter' ), 10 );
 
-		$this->assertEquals( $url, $this->fakeURL );
+		$this->assertEquals( $url, $this->fake_url );
 	}
 	public function get_avatar_url_filter( $url ) {
-		return $this->fakeURL;
+		return $this->fake_url;
 	}
 
 	/**
@@ -207,37 +207,37 @@ class Tests_Avatar extends WP_UnitTestCase {
 	}
 
 
-	protected $fakeIMG;
+	protected $fake_img;
 	/**
 	 * @ticket 21195
 	 */
 	public function test_pre_get_avatar_filter() {
-		$this->fakeIMG = 'YOU TOO?!';
+		$this->fake_img = 'YOU TOO?!';
 
 		add_filter( 'pre_get_avatar', array( $this, 'pre_get_avatar_filter' ), 10, 1 );
 		$img = get_avatar( 1 );
 		remove_filter( 'pre_get_avatar', array( $this, 'pre_get_avatar_filter' ), 10 );
 
-		$this->assertEquals( $img, $this->fakeIMG );
+		$this->assertEquals( $img, $this->fake_img );
 	}
 	public function pre_get_avatar_filter( $img ) {
-		return $this->fakeIMG;
+		return $this->fake_img;
 	}
 
 	/**
 	 * @ticket 21195
 	 */
 	public function test_get_avatar_filter() {
-		$this->fakeURL = 'YA RLY';
+		$this->fake_url = 'YA RLY';
 
 		add_filter( 'get_avatar', array( $this, 'get_avatar_filter' ), 10, 1 );
 		$img = get_avatar( 1 );
 		remove_filter( 'get_avatar', array( $this, 'get_avatar_filter' ), 10 );
 
-		$this->assertEquals( $img, $this->fakeURL );
+		$this->assertEquals( $img, $this->fake_url );
 	}
 	public function get_avatar_filter( $img ) {
-		return $this->fakeURL;
+		return $this->fake_url;
 	}
 
 	/**
diff --git a/tests/phpunit/tests/functions.php b/tests/phpunit/tests/functions.php
index 7dcea34533..453d3c8ad8 100644
--- a/tests/phpunit/tests/functions.php
+++ b/tests/phpunit/tests/functions.php
@@ -7,7 +7,7 @@ class Tests_Functions extends WP_UnitTestCase {
 	function test_wp_parse_args_object() {
 		$x        = new MockClass;
 		$x->_baba = 5;
-		$x->yZ    = 'baba';
+		$x->yZ    = 'baba'; // phpcs:ignore WordPress.NamingConventions.ValidVariableName.NotSnakeCaseMemberVar
 		$x->a     = array( 5, 111, 'x' );
 		$this->assertEquals(
 			array(
@@ -43,7 +43,7 @@ class Tests_Functions extends WP_UnitTestCase {
 	function test_wp_parse_args_defaults() {
 		$x        = new MockClass;
 		$x->_baba = 5;
-		$x->yZ    = 'baba';
+		$x->yZ    = 'baba'; // phpcs:ignore WordPress.NamingConventions.ValidVariableName.NotSnakeCaseMemberVar
 		$x->a     = array( 5, 111, 'x' );
 		$d        = array( 'pu' => 'bu' );
 		$this->assertEquals(
diff --git a/tests/phpunit/tests/general/wpError.php b/tests/phpunit/tests/general/wpError.php
index dde4baad8c..3fccc470c8 100644
--- a/tests/phpunit/tests/general/wpError.php
+++ b/tests/phpunit/tests/general/wpError.php
@@ -14,7 +14,7 @@ class Tests_WP_Error extends WP_UnitTestCase {
 	 *
 	 * @var WP_Error
 	 */
-	public $WP_Error;
+	public $wp_error;
 
 	/**
 	 * Set up.
@@ -22,27 +22,27 @@ class Tests_WP_Error extends WP_UnitTestCase {
 	public function setUp() {
 		parent::setUp();
 
-		$this->WP_Error = new WP_Error();
+		$this->wp_error = new WP_Error();
 	}
 
 	public function test_WP_Error_should_be_of_type_WP_Error() {
-		$this->assertWPError( $this->WP_Error );
+		$this->assertWPError( $this->wp_error );
 	}
 
 	public function test_WP_Error_with_default_empty_parameters_should_add_no_errors() {
-		$this->assertEmpty( $this->WP_Error->errors );
+		$this->assertEmpty( $this->wp_error->errors );
 	}
 
 	public function test_WP_Error_with_empty_code_should_add_no_code() {
-		$this->assertSame( '', $this->WP_Error->get_error_code() );
+		$this->assertSame( '', $this->wp_error->get_error_code() );
 	}
 
 	public function test_WP_Error_with_empty_code_should_add_no_message() {
-		$this->assertSame( '', $this->WP_Error->get_error_message() );
+		$this->assertSame( '', $this->wp_error->get_error_message() );
 	}
 
 	public function test_WP_Error_with_empty_code_should_add_no_error_data() {
-		$this->assertEmpty( $this->WP_Error->error_data );
+		$this->assertEmpty( $this->wp_error->error_data );
 	}
 
 	public function test_WP_Error_with_code_and_empty_message_should_add_error_with_that_code() {
@@ -103,195 +103,195 @@ class Tests_WP_Error extends WP_UnitTestCase {
 	 * @covers ::get_error_codes()
 	 */
 	public function test_get_error_codes_with_no_errors_should_return_empty_array() {
-		$this->assertEmpty( $this->WP_Error->get_error_codes() );
+		$this->assertEmpty( $this->wp_error->get_error_codes() );
 	}
 
 	/**
 	 * @covers ::get_error_codes()
 	 */
 	public function test_get_error_codes_with_one_error_should_return_an_array_with_only_that_code() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->assertEqualSets( array( 'code' ), $this->WP_Error->get_error_codes() );
+		$this->assertEqualSets( array( 'code' ), $this->wp_error->get_error_codes() );
 	}
 
 	/**
 	 * @covers ::get_error_codes()
 	 */
 	public function test_get_error_codes_with_multiple_errors_should_return_an_array_of_those_codes() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add( 'code2', 'message2' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add( 'code2', 'message2' );
 
 		$expected = array( 'code', 'code2' );
 
-		$this->assertEqualSets( $expected, $this->WP_Error->get_error_codes() );
+		$this->assertEqualSets( $expected, $this->wp_error->get_error_codes() );
 	}
 
 	/**
 	 * @covers ::get_error_code()
 	 */
 	public function test_get_error_code_with_no_errors_should_return_an_empty_string() {
-		$this->assertSame( '', $this->WP_Error->get_error_code() );
+		$this->assertSame( '', $this->wp_error->get_error_code() );
 	}
 
 	/**
 	 * @covers ::get_error_code()
 	 */
 	public function test_get_error_code_with_one_error_should_return_that_error_code() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->assertSame( 'code', $this->WP_Error->get_error_code() );
+		$this->assertSame( 'code', $this->wp_error->get_error_code() );
 	}
 
 	/**
 	 * @covers ::get_error_code()
 	 */
 	public function test_get_error_code_with_multiple_errors_should_return_only_the_first_error_code() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add( 'code2', 'message2' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add( 'code2', 'message2' );
 
-		$this->assertSame( 'code', $this->WP_Error->get_error_code() );
+		$this->assertSame( 'code', $this->wp_error->get_error_code() );
 	}
 
 	/**
 	 * @covers ::get_error_messages()
 	 */
 	public function test_get_error_messages_with_empty_code_and_no_errors_should_return_an_empty_array() {
-		$this->assertEmpty( $this->WP_Error->get_error_messages() );
+		$this->assertEmpty( $this->wp_error->get_error_messages() );
 	}
 
 	/**
 	 * @covers ::get_error_messages()
 	 */
 	public function test_get_error_messages_with_empty_code_one_error_should_return_an_array_with_that_message() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->assertEqualSets( array( 'message' ), $this->WP_Error->get_error_messages() );
+		$this->assertEqualSets( array( 'message' ), $this->wp_error->get_error_messages() );
 	}
 
 	/**
 	 * @covers ::get_error_messages()
 	 */
 	public function test_get_error_messages_with_empty_code_multiple_errors_should_return_an_array_of_messages() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add( 'code2', 'message2' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add( 'code2', 'message2' );
 
-		$this->assertEqualSets( array( 'message', 'message2' ), $this->WP_Error->get_error_messages() );
+		$this->assertEqualSets( array( 'message', 'message2' ), $this->wp_error->get_error_messages() );
 	}
 
 	/**
 	 * @covers ::get_error_messages()
 	 */
 	public function test_get_error_messages_with_an_invalid_code_should_return_an_empty_array() {
-		$this->assertEmpty( $this->WP_Error->get_error_messages( 'code' ) );
+		$this->assertEmpty( $this->wp_error->get_error_messages( 'code' ) );
 	}
 
 	/**
 	 * @covers ::get_error_messages()
 	 */
 	public function test_get_error_messages_with_one_error_should_return_an_array_with_that_message() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->assertEqualSets( array( 'message' ), $this->WP_Error->get_error_messages( 'code' ) );
+		$this->assertEqualSets( array( 'message' ), $this->wp_error->get_error_messages( 'code' ) );
 	}
 
 	/**
 	 * @covers ::get_error_messages()
 	 */
 	public function test_get_error_messages_with_multiple_errors_same_code_should_return_an_array_with_all_messages() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add( 'code', 'message2' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message2' );
 
-		$this->assertequalSets( array( 'message', 'message2' ), $this->WP_Error->get_error_messages( 'code' ) );
+		$this->assertequalSets( array( 'message', 'message2' ), $this->wp_error->get_error_messages( 'code' ) );
 	}
 
 	/**
 	 * @covers ::get_error_message()
 	 */
 	public function test_get_error_message_with_empty_code_and_no_errors_should_return_an_empty_string() {
-		$this->assertSame( '', $this->WP_Error->get_error_message() );
+		$this->assertSame( '', $this->wp_error->get_error_message() );
 	}
 
 	/**
 	 * @covers ::get_error_message()
 	 */
 	public function test_get_error_message_with_empty_code_and_one_error_should_return_that_message() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->assertSame( 'message', $this->WP_Error->get_error_message() );
+		$this->assertSame( 'message', $this->wp_error->get_error_message() );
 	}
 
 	/**
 	 * @covers ::get_error_message()
 	 */
 	public function test_get_error_message_with_empty_code_and_multiple_errors_should_return_the_first_message() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add( 'code2', 'message2' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add( 'code2', 'message2' );
 
-		$this->assertSame( 'message', $this->WP_Error->get_error_message() );
+		$this->assertSame( 'message', $this->wp_error->get_error_message() );
 	}
 
 	/**
 	 * @covers ::get_error_message()
 	 */
 	public function test_get_error_message_with_empty_code_and_multiple_errors_multiple_codes_should_return_the_first_message() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add( 'code2', 'message2' );
-		$this->WP_Error->add( 'code', 'message2' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add( 'code2', 'message2' );
+		$this->wp_error->add( 'code', 'message2' );
 
-		$this->assertSame( 'message', $this->WP_Error->get_error_message() );
+		$this->assertSame( 'message', $this->wp_error->get_error_message() );
 	}
 
 	/**
 	 * @covers ::get_error_message()
 	 */
 	public function test_get_error_message_with_invalid_code_and_no_errors_should_return_empty_string() {
-		$this->assertSame( '', $this->WP_Error->get_error_message( 'invalid' ) );
+		$this->assertSame( '', $this->wp_error->get_error_message( 'invalid' ) );
 	}
 
 	/**
 	 * @covers ::get_error_message()
 	 */
 	public function test_get_error_message_with_invalid_code_and_one_error_should_return_an_empty_string() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->assertSame( '', $this->WP_Error->get_error_message( 'invalid' ) );
+		$this->assertSame( '', $this->wp_error->get_error_message( 'invalid' ) );
 	}
 
 	/**
 	 * @covers ::get_error_message()
 	 */
 	public function test_get_error_message_with_invalid_code_and_multiple_errors_should_return_an_empty_string() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add( 'code2', 'message2' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add( 'code2', 'message2' );
 
-		$this->assertSame( '', $this->WP_Error->get_error_message( 'invalid' ) );
+		$this->assertSame( '', $this->wp_error->get_error_message( 'invalid' ) );
 	}
 
 	/**
 	 * @covers ::get_error_data()
 	 */
 	public function test_get_error_data_with_empty_code_and_no_errors_should_evaluate_as_null() {
-		$this->assertSame( null, $this->WP_Error->get_error_data() );
+		$this->assertSame( null, $this->wp_error->get_error_data() );
 	}
 
 	/**
 	 * @covers ::get_error_data()
 	 */
 	public function test_get_error_data_with_empty_code_one_error_no_data_should_evaluate_as_null() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->assertSame( null, $this->WP_Error->get_error_data() );
+		$this->assertSame( null, $this->wp_error->get_error_data() );
 	}
 
 	/**
 	 * @covers ::get_error_data()
 	 */
 	public function test_get_error_data_with_empty_code_multiple_errors_no_data_should_evaluate_as_null() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add( 'code2', 'message2' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add( 'code2', 'message2' );
 
-		$this->assertSame( null, $this->WP_Error->get_error_data() );
+		$this->assertSame( null, $this->wp_error->get_error_data() );
 	}
 
 	/**
@@ -299,9 +299,9 @@ class Tests_WP_Error extends WP_UnitTestCase {
 	 */
 	public function test_get_error_data_with_empty_code_and_one_error_with_data_should_return_that_data() {
 		$expected = array( 'data-key' => 'data-value' );
-		$this->WP_Error->add( 'code', 'message', $expected );
+		$this->wp_error->add( 'code', 'message', $expected );
 
-		$this->assertEqualSetsWithIndex( $expected, $this->WP_Error->get_error_data() );
+		$this->assertEqualSetsWithIndex( $expected, $this->wp_error->get_error_data() );
 	}
 
 	/**
@@ -309,37 +309,37 @@ class Tests_WP_Error extends WP_UnitTestCase {
 	 */
 	public function test_get_error_data_with_empty_code_and_multiple_errors_different_codes_should_return_the_last_data_of_the_first_code() {
 		$expected = array( 'data-key' => 'data-value' );
-		$this->WP_Error->add( 'code', 'message', $expected );
-		$this->WP_Error->add( 'code2', 'message2', 'data2' );
+		$this->wp_error->add( 'code', 'message', $expected );
+		$this->wp_error->add( 'code2', 'message2', 'data2' );
 
-		$this->assertEqualSetsWithIndex( $expected, $this->WP_Error->get_error_data() );
+		$this->assertEqualSetsWithIndex( $expected, $this->wp_error->get_error_data() );
 	}
 
 	/**
 	 * @covers ::get_error_data()
 	 */
 	public function test_get_error_data_with_empty_code_and_multiple_errors_same_code_should_return_the_last_data_of_the_first_code() {
-		$this->WP_Error->add( 'code', 'message', 'data' );
-		$this->WP_Error->add( 'code', 'message2', 'data2' );
-		$this->WP_Error->add( 'code2', 'message2', 'data3' );
+		$this->wp_error->add( 'code', 'message', 'data' );
+		$this->wp_error->add( 'code', 'message2', 'data2' );
+		$this->wp_error->add( 'code2', 'message2', 'data3' );
 
-		$this->assertSame( 'data2', $this->WP_Error->get_error_data() );
+		$this->assertSame( 'data2', $this->wp_error->get_error_data() );
 	}
 
 	/**
 	 * @covers ::get_error_data()
 	 */
 	public function test_get_error_data_with_code_and_no_errors_should_evaluate_as_null() {
-		$this->assertSame( null, $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( null, $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::get_error_data()
 	 */
 	public function test_get_error_data_with_code_and_one_error_with_no_data_should_evaluate_as_null() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->assertSame( null, $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( null, $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
@@ -347,9 +347,9 @@ class Tests_WP_Error extends WP_UnitTestCase {
 	 */
 	public function test_get_error_data_with_code_and_one_error_with_data_should_return_that_data() {
 		$expected = array( 'data-key' => 'data-value' );
-		$this->WP_Error->add( 'code', 'message', $expected );
+		$this->wp_error->add( 'code', 'message', $expected );
 
-		$this->assertEqualSetsWithIndex( $expected, $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertEqualSetsWithIndex( $expected, $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
@@ -357,300 +357,300 @@ class Tests_WP_Error extends WP_UnitTestCase {
 	 */
 	public function test_get_error_data_with_code_and_multiple_errors_different_codes_should_return_the_last_stored_data_of_the_code() {
 		$expected = array( 'data3' );
-		$this->WP_Error->add( 'code', 'message', 'data' );
-		$this->WP_Error->add( 'code2', 'message2', 'data2' );
-		$this->WP_Error->add( 'code', 'message3', $expected );
+		$this->wp_error->add( 'code', 'message', 'data' );
+		$this->wp_error->add( 'code2', 'message2', 'data2' );
+		$this->wp_error->add( 'code', 'message3', $expected );
 
-		$this->assertEqualSetsWithIndex( $expected, $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertEqualSetsWithIndex( $expected, $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::get_error_data()
 	 */
 	public function test_get_error_data_with_code_and_multiple_errors_same_code_should_return_the_last_stored_data() {
-		$this->WP_Error->add( 'code', 'message', 'data' );
-		$this->WP_Error->add( 'code', 'message2', 'data2' );
-		$this->WP_Error->add( 'code2', 'message3', 'data3' );
+		$this->wp_error->add( 'code', 'message', 'data' );
+		$this->wp_error->add( 'code', 'message2', 'data2' );
+		$this->wp_error->add( 'code2', 'message3', 'data3' );
 
-		$this->assertSame( 'data2', $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( 'data2', $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::has_errors()
 	 */
 	public function test_has_errors_with_no_errors_returns_false() {
-		$this->assertFalse( $this->WP_Error->has_errors() );
+		$this->assertFalse( $this->wp_error->has_errors() );
 	}
 
 	/**
 	 * @covers ::has_errors()
 	 */
 	public function test_has_errors_with_errors_returns_true() {
-		$this->WP_Error->add( 'code', 'message', 'data' );
-		$this->assertTrue( $this->WP_Error->has_errors() );
+		$this->wp_error->add( 'code', 'message', 'data' );
+		$this->assertTrue( $this->wp_error->has_errors() );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_empty_code_empty_message_empty_data_should_add_empty_key_to_errors_array() {
-		$this->WP_Error->add( '', '', 'data' );
+		$this->wp_error->add( '', '', 'data' );
 
-		$this->assertArrayHasKey( '', $this->WP_Error->errors );
+		$this->assertArrayHasKey( '', $this->wp_error->errors );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_empty_code_empty_message_empty_data_should_add_empty_message_to_errors_array_under_empty_key() {
-		$this->WP_Error->add( '', '', 'data' );
+		$this->wp_error->add( '', '', 'data' );
 
-		$this->assertEqualSetsWithIndex( array( '' => array( '' ) ), $this->WP_Error->errors );
+		$this->assertEqualSetsWithIndex( array( '' => array( '' ) ), $this->wp_error->errors );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_empty_code_empty_message_empty_data_should_not_alter_data() {
-		$this->WP_Error->add( '', '', '' );
+		$this->wp_error->add( '', '', '' );
 
-		$this->assertEmpty( $this->WP_Error->error_data );
+		$this->assertEmpty( $this->wp_error->error_data );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_empty_code_empty_message_non_empty_data_should_store_data_under_an_empty_code_key() {
-		$this->WP_Error->add( '', '', 'data' );
+		$this->wp_error->add( '', '', 'data' );
 
-		$this->assertEqualSetsWithIndex( array( '' => 'data' ), $this->WP_Error->error_data );
+		$this->assertEqualSetsWithIndex( array( '' => 'data' ), $this->wp_error->error_data );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_code_empty_message_empty_data_should_add_error_with_code() {
-		$this->WP_Error->add( 'code', '' );
+		$this->wp_error->add( 'code', '' );
 
-		$this->assertSame( 'code', $this->WP_Error->get_error_code() );
+		$this->assertSame( 'code', $this->wp_error->get_error_code() );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_code_empty_message_empty_data_should_add_error_with_empty_message() {
-		$this->WP_Error->add( 'code', '' );
+		$this->wp_error->add( 'code', '' );
 
-		$this->assertSame( '', $this->WP_Error->get_error_message( 'code' ) );
+		$this->assertSame( '', $this->wp_error->get_error_message( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_code_empty_message_empty_data_should_not_add_error_data() {
-		$this->WP_Error->add( 'code', '' );
+		$this->wp_error->add( 'code', '' );
 
-		$this->assertSame( null, $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( null, $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_code_and_message_and_empty_data_should_should_add_error_with_that_message() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->assertSame( 'message', $this->WP_Error->get_error_message( 'code' ) );
+		$this->assertSame( 'message', $this->wp_error->get_error_message( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_code_and_message_and_empty_data_should_not_alter_stored_data() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->assertSame( null, $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( null, $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_code_and_empty_message_and_data_should_add_error_with_that_code() {
-		$this->WP_Error->add( 'code', '', 'data' );
+		$this->wp_error->add( 'code', '', 'data' );
 
-		$this->assertSame( 'code', $this->WP_Error->get_error_code() );
+		$this->assertSame( 'code', $this->wp_error->get_error_code() );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_code_and_empty_message_and_data_should_store_that_data() {
-		$this->WP_Error->add( 'code', '', 'data' );
+		$this->wp_error->add( 'code', '', 'data' );
 
-		$this->assertSame( 'data', $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( 'data', $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_code_and_message_and_data_should_add_an_error_with_that_code() {
-		$this->WP_Error->add( 'code', 'message', 'data' );
+		$this->wp_error->add( 'code', 'message', 'data' );
 
-		$this->assertSame( 'code', $this->WP_Error->get_error_code() );
+		$this->assertSame( 'code', $this->wp_error->get_error_code() );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_code_and_message_and_data_should_add_an_error_with_that_message() {
-		$this->WP_Error->add( 'code', 'message', 'data' );
+		$this->wp_error->add( 'code', 'message', 'data' );
 
-		$this->assertSame( 'message', $this->WP_Error->get_error_message( 'code' ) );
+		$this->assertSame( 'message', $this->wp_error->get_error_message( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_with_code_and_message_and_data_should_store_that_data() {
-		$this->WP_Error->add( 'code', 'message', 'data' );
+		$this->wp_error->add( 'code', 'message', 'data' );
 
-		$this->assertSame( 'data', $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( 'data', $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_multiple_times_with_the_same_code_should_add_additional_messages_for_that_code() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add( 'code', 'message2' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message2' );
 
 		$expected = array( 'message', 'message2' );
 
-		$this->assertEqualSets( $expected, $this->WP_Error->get_error_messages( 'code' ) );
+		$this->assertEqualSets( $expected, $this->wp_error->get_error_messages( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add()
 	 */
 	public function test_add_multiple_times_with_the_same_code_and_different_data_should_store_only_the_last_added_data() {
-		$this->WP_Error->add( 'code', 'message', 'data-bar' );
-		$this->WP_Error->add( 'code', 'message2', 'data-baz' );
+		$this->wp_error->add( 'code', 'message', 'data-bar' );
+		$this->wp_error->add( 'code', 'message2', 'data-baz' );
 
-		$this->assertSame( 'data-baz', $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( 'data-baz', $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add_data()
 	 */
 	public function test_add_data_with_empty_data_empty_code_should_create_orphaned_data_with_no_error() {
-		$this->WP_Error->add_data( '' );
+		$this->wp_error->add_data( '' );
 
-		$this->assertEmpty( $this->WP_Error->errors );
+		$this->assertEmpty( $this->wp_error->errors );
 	}
 
 	/**
 	 * @covers ::add_data()
 	 */
 	public function test_add_data_with_empty_data_empty_code_no_errors_should_create_data_under_an_empty_code_key() {
-		$this->WP_Error->add_data( '' );
+		$this->wp_error->add_data( '' );
 
-		$this->assertEqualSets( array( '' => '' ), $this->WP_Error->error_data );
+		$this->assertEqualSets( array( '' => '' ), $this->wp_error->error_data );
 	}
 
 	/**
 	 * @covers ::add_data()
 	 */
 	public function test_add_data_with_data_empty_code_and_one_error_should_store_the_data_under_that_code() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add_data( 'data' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add_data( 'data' );
 
-		$this->assertSame( 'data', $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( 'data', $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add_data()
 	 */
 	public function test_add_data_with_data_empty_code_and_multiple_errors_with_different_codes_should_store_it_under_the_first_code() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add( 'code2', 'message2' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add( 'code2', 'message2' );
 
-		$this->WP_Error->add_data( 'data' );
+		$this->wp_error->add_data( 'data' );
 
-		$this->assertSame( 'data', $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( 'data', $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add_data()
 	 */
 	public function test_add_data_with_data_empty_code_and_multiple_errors_with_same_code_should_store_it_under_the_first_code() {
-		$this->WP_Error->add( 'code', 'message' );
-		$this->WP_Error->add( 'code2', 'message2' );
-		$this->WP_Error->add( 'code', 'message3' );
+		$this->wp_error->add( 'code', 'message' );
+		$this->wp_error->add( 'code2', 'message2' );
+		$this->wp_error->add( 'code', 'message3' );
 
-		$this->WP_Error->add_data( 'data' );
+		$this->wp_error->add_data( 'data' );
 
-		$this->assertSame( 'data', $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( 'data', $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::add_data()
 	 */
 	public function test_add_data_with_data_and_code_and_no_errors_should_create_orphaned_data_with_no_error() {
-		$this->WP_Error->add_data( 'data', 'code' );
+		$this->wp_error->add_data( 'data', 'code' );
 
-		$this->assertEmpty( $this->WP_Error->errors );
+		$this->assertEmpty( $this->wp_error->errors );
 	}
 
 	/**
 	 * @covers ::add_data()
 	 */
 	public function test_add_data_with_data_and_code_no_errors_should_create_data_under_that_code_key() {
-		$this->WP_Error->add_data( 'data', 'code' );
+		$this->wp_error->add_data( 'data', 'code' );
 
-		$this->assertEqualSets( array( 'code' => 'data' ), $this->WP_Error->error_data );
+		$this->assertEqualSets( array( 'code' => 'data' ), $this->wp_error->error_data );
 	}
 
 	/**
 	 * @covers ::add_data()
 	 */
 	public function test_add_data_with_data_and_code_one_error_different_code_should_create_orphaned_data_with_no_error() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->WP_Error->add_data( 'data', 'code2' );
+		$this->wp_error->add_data( 'data', 'code2' );
 
-		$this->assertEqualSetsWithIndex( array( 'code' => array( 'message' ) ), $this->WP_Error->errors );
+		$this->assertEqualSetsWithIndex( array( 'code' => array( 'message' ) ), $this->wp_error->errors );
 	}
 
 	/**
 	 * @covers ::add_data()
 	 */
 	public function test_add_data_with_data_and_code_one_error_different_code_should_create_data_under_that_code_key() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->WP_Error->add_data( 'data', 'code2' );
+		$this->wp_error->add_data( 'data', 'code2' );
 
-		$this->assertEqualSetsWithIndex( array( 'code2' => 'data' ), $this->WP_Error->error_data );
+		$this->assertEqualSetsWithIndex( array( 'code2' => 'data' ), $this->wp_error->error_data );
 	}
 
 	/**
 	 * @covers ::add_data()
 	 */
 	public function test_add_data_with_data_and_code_should_add_data() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->WP_Error->add_data( 'data', 'code' );
+		$this->wp_error->add_data( 'data', 'code' );
 
-		$this->assertSame( 'data', $this->WP_Error->get_error_data( 'code' ) );
+		$this->assertSame( 'data', $this->wp_error->get_error_data( 'code' ) );
 	}
 
 	/**
 	 * @covers ::remove()
 	 */
 	public function test_remove_with_no_errors_should_affect_nothing() {
-		$before = $this->WP_Error->errors;
+		$before = $this->wp_error->errors;
 
-		$this->WP_Error->remove( 'code' );
+		$this->wp_error->remove( 'code' );
 
-		$after = $this->WP_Error->errors;
+		$after = $this->wp_error->errors;
 
 		$this->assertEqualSetsWithIndex( $before, $after );
 	}
@@ -659,11 +659,11 @@ class Tests_WP_Error extends WP_UnitTestCase {
 	 * @covers ::remove()
 	 */
 	public function test_remove_empty_code_no_errors_should_affect_nothing() {
-		$before = $this->WP_Error->errors;
+		$before = $this->wp_error->errors;
 
-		$this->WP_Error->remove( '' );
+		$this->wp_error->remove( '' );
 
-		$after = $this->WP_Error->errors;
+		$after = $this->wp_error->errors;
 
 		$this->assertEqualSetsWithIndex( $before, $after );
 	}
@@ -672,13 +672,13 @@ class Tests_WP_Error extends WP_UnitTestCase {
 	 * @covers ::remove()
 	 */
 	public function test_remove_empty_code_and_one_error_with_empty_string_code_should_remove_error() {
-		$before = $this->WP_Error->errors;
+		$before = $this->wp_error->errors;
 
-		$this->WP_Error->add( '', 'message' );
+		$this->wp_error->add( '', 'message' );
 
-		$this->WP_Error->remove( '' );
+		$this->wp_error->remove( '' );
 
-		$after = $this->WP_Error->errors;
+		$after = $this->wp_error->errors;
 
 		$this->assertEqualSetsWithIndex( $before, $after );
 	}
@@ -687,35 +687,35 @@ class Tests_WP_Error extends WP_UnitTestCase {
 	 * @covers ::remove()
 	 */
 	public function test_remove_empty_code_and_one_error_with_empty_string_code_should_remove_error_data() {
-		$this->WP_Error->add( '', 'message', 'data' );
+		$this->wp_error->add( '', 'message', 'data' );
 
-		$this->WP_Error->remove( '' );
+		$this->wp_error->remove( '' );
 
-		$after = $this->WP_Error->error_data;
+		$after = $this->wp_error->error_data;
 
-		$this->assertEmpty( $this->WP_Error->error_data );
+		$this->assertEmpty( $this->wp_error->error_data );
 	}
 
 	/**
 	 * @covers ::remove()
 	 */
 	public function test_remove_should_remove_the_error_with_the_given_code() {
-		$this->WP_Error->add( 'code', 'message' );
+		$this->wp_error->add( 'code', 'message' );
 
-		$this->WP_Error->remove( 'code' );
+		$this->wp_error->remove( 'code' );
 
-		$this->assertEmpty( $this->WP_Error->errors );
+		$this->assertEmpty( $this->wp_error->errors );
 	}
 
 	/**
 	 * @covers ::remove()
 	 */
 	public function test_remove_should_remove_the_error_data_associated_with_the_given_code() {
-		$this->WP_Error->add( 'code', 'message', 'data' );
+		$this->wp_error->add( 'code', 'message', 'data' );
 
-		$this->WP_Error->remove( 'code' );
+		$this->wp_error->remove( 'code' );
 
-		$this->assertEmpty( $this->WP_Error->error_data );
+		$this->assertEmpty( $this->wp_error->error_data );
 	}
 
 }
diff --git a/tests/phpunit/tests/http/base.php b/tests/phpunit/tests/http/base.php
index ad6027e58d..011870f836 100644
--- a/tests/phpunit/tests/http/base.php
+++ b/tests/phpunit/tests/http/base.php
@@ -13,7 +13,7 @@
 abstract class WP_HTTP_UnitTestCase extends WP_UnitTestCase {
 	// You can use your own version of data/WPHTTP-testcase-redirection-script.php here.
 	var $redirection_script = 'http://api.wordpress.org/core/tests/1.0/redirection.php';
-	var $fileStreamUrl      = 'http://s.w.org/screenshots/3.9/dashboard.png';
+	var $file_stream_url    = 'http://s.w.org/screenshots/3.9/dashboard.png';
 
 	protected $http_request_args;
 
@@ -254,7 +254,7 @@ abstract class WP_HTTP_UnitTestCase extends WP_UnitTestCase {
 	}
 
 	function test_file_stream() {
-		$url  = $this->fileStreamUrl;
+		$url  = $this->file_stream_url;
 		$size = 153204;
 		$res  = wp_remote_request(
 			$url,
@@ -282,7 +282,7 @@ abstract class WP_HTTP_UnitTestCase extends WP_UnitTestCase {
 	 * @ticket 26726
 	 */
 	function test_file_stream_limited_size() {
-		$url  = $this->fileStreamUrl;
+		$url  = $this->file_stream_url;
 		$size = 10000;
 		$res  = wp_remote_request(
 			$url,
@@ -311,7 +311,7 @@ abstract class WP_HTTP_UnitTestCase extends WP_UnitTestCase {
 	 * @ticket 31172
 	 */
 	function test_request_limited_size() {
-		$url  = $this->fileStreamUrl;
+		$url  = $this->file_stream_url;
 		$size = 10000;
 
 		$res = wp_remote_request(
diff --git a/tests/phpunit/tests/http/curl.php b/tests/phpunit/tests/http/curl.php
index a5b24f467a..f64cace2b7 100644
--- a/tests/phpunit/tests/http/curl.php
+++ b/tests/phpunit/tests/http/curl.php
@@ -15,7 +15,7 @@ class Tests_HTTP_curl extends WP_HTTP_UnitTestCase {
 	public function test_http_api_curl_stream_parameter_is_a_reference() {
 		add_action( 'http_api_curl', array( $this, '_action_test_http_api_curl_stream_parameter_is_a_reference' ), 10, 3 );
 		wp_remote_request(
-			$this->fileStreamUrl,
+			$this->file_stream_url,
 			array(
 				'stream'  => true,
 				'timeout' => 30,
diff --git a/tests/phpunit/tests/user.php b/tests/phpunit/tests/user.php
index 4f9fa2ba1b..c6b4d8b7e9 100644
--- a/tests/phpunit/tests/user.php
+++ b/tests/phpunit/tests/user.php
@@ -199,6 +199,7 @@ class Tests_User extends WP_UnitTestCase {
 	 * @ticket 20043
 	 */
 	public function test_user_unset() {
+		// phpcs:disable WordPress.NamingConventions.ValidVariableName.NotSnakeCaseMemberVar
 		$user = new WP_User( self::$author_id );
 
 		// Test custom fields
@@ -207,6 +208,7 @@ class Tests_User extends WP_UnitTestCase {
 		unset( $user->customField );
 		$this->assertFalse( isset( $user->customField ) );
 		return $user;
+		// phpcs:enable
 	}
 
 	/**