diff --git a/tests/phpunit/tests/compat/mbStrlen.php b/tests/phpunit/tests/compat/mbStrlen.php
index 8d9d73108d83a..4be968e3f39ce 100644
--- a/tests/phpunit/tests/compat/mbStrlen.php
+++ b/tests/phpunit/tests/compat/mbStrlen.php
@@ -13,8 +13,9 @@ class Tests_Compat_mbStrlen extends WP_UnitTestCase {
 	 * Test that the native mb_strlen() is available.
 	 */
 	public function test_mb_strlen_availability() {
-		$this->assertTrue(
-			in_array( 'mb_strlen', get_defined_functions()['internal'], true ),
+		$this->assertContains(
+			'mb_strlen',
+			get_defined_functions()['internal'],
 			'Test runner should have `mbstring` extension active but doesn’t.'
 		);
 	}
diff --git a/tests/phpunit/tests/compat/mbSubstr.php b/tests/phpunit/tests/compat/mbSubstr.php
index 5cc4b3d6778a7..5aee9616b16d1 100644
--- a/tests/phpunit/tests/compat/mbSubstr.php
+++ b/tests/phpunit/tests/compat/mbSubstr.php
@@ -13,8 +13,9 @@ class Tests_Compat_mbSubstr extends WP_UnitTestCase {
 	 * Test that mb_substr() is always available (either from PHP or WP).
 	 */
 	public function test_mb_substr_availability() {
-		$this->assertTrue(
-			in_array( 'mb_substr', get_defined_functions()['internal'], true ),
+		$this->assertContains(
+			'mb_substr',
+			get_defined_functions()['internal'],
 			'Test runner should have `mbstring` extension active but doesn’t.'
 		);
 	}
diff --git a/tests/phpunit/tests/post/types.php b/tests/phpunit/tests/post/types.php
index 96519586d6cff..2c8564f22aeab 100644
--- a/tests/phpunit/tests/post/types.php
+++ b/tests/phpunit/tests/post/types.php
@@ -343,7 +343,7 @@ public function test_unregister_post_type_removes_query_vars() {
 
 		$this->assertIsInt( array_search( 'bar', $wp->public_query_vars, true ) );
 		$this->assertTrue( unregister_post_type( 'foo' ) );
-		$this->assertFalse( array_search( 'bar', $wp->public_query_vars, true ) );
+		$this->assertNotContains( 'bar', $wp->public_query_vars );
 	}
 
 	/**
@@ -463,8 +463,8 @@ public function test_unregister_post_type_removes_post_type_from_taxonomies() {
 		$this->assertIsInt( array_search( 'foo', $wp_taxonomies['category']->object_type, true ) );
 		$this->assertIsInt( array_search( 'foo', $wp_taxonomies['post_tag']->object_type, true ) );
 		$this->assertTrue( unregister_post_type( 'foo' ) );
-		$this->assertFalse( array_search( 'foo', $wp_taxonomies['category']->object_type, true ) );
-		$this->assertFalse( array_search( 'foo', $wp_taxonomies['post_tag']->object_type, true ) );
+		$this->assertNotContains( 'foo', $wp_taxonomies['category']->object_type );
+		$this->assertNotContains( 'foo', $wp_taxonomies['post_tag']->object_type );
 		$this->assertEmpty( get_object_taxonomies( 'foo' ) );
 	}
 
diff --git a/tests/phpunit/tests/post/wpPostType.php b/tests/phpunit/tests/post/wpPostType.php
index 23ec325a65a54..361ed0343ad0d 100644
--- a/tests/phpunit/tests/post/wpPostType.php
+++ b/tests/phpunit/tests/post/wpPostType.php
@@ -173,8 +173,8 @@ public function test_adds_rewrite_rules() {
 		$post_type_object->remove_rewrite_rules();
 		$rewrite_tags_after = $wp_rewrite->rewritecode;
 
-		$this->assertNotFalse( array_search( "%$post_type%", $rewrite_tags, true ) );
-		$this->assertFalse( array_search( "%$post_type%", $rewrite_tags_after, true ) );
+		$this->assertContains( "%$post_type%", $rewrite_tags );
+		$this->assertNotContains( "%$post_type%", $rewrite_tags_after );
 	}
 
 	public function test_register_meta_boxes() {
diff --git a/tests/phpunit/tests/taxonomy.php b/tests/phpunit/tests/taxonomy.php
index 13528c3015c6b..39a1a6d90ed5b 100644
--- a/tests/phpunit/tests/taxonomy.php
+++ b/tests/phpunit/tests/taxonomy.php
@@ -895,7 +895,7 @@ public function test_unregister_taxonomy_removes_query_vars() {
 
 		$this->assertIsInt( array_search( 'bar', $wp->public_query_vars, true ) );
 		$this->assertTrue( unregister_taxonomy( 'foo' ) );
-		$this->assertFalse( array_search( 'bar', $wp->public_query_vars, true ) );
+		$this->assertNotContains( 'bar', $wp->public_query_vars );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/term/wpTaxonomy.php b/tests/phpunit/tests/term/wpTaxonomy.php
index 845497ad0672a..a919e095aa8eb 100644
--- a/tests/phpunit/tests/term/wpTaxonomy.php
+++ b/tests/phpunit/tests/term/wpTaxonomy.php
@@ -76,8 +76,8 @@ public function test_adds_rewrite_rules() {
 		$taxonomy_object->remove_rewrite_rules();
 		$rewrite_tags_after = $wp_rewrite->rewritecode;
 
-		$this->assertNotFalse( array_search( "%$taxonomy%", $rewrite_tags, true ) );
-		$this->assertFalse( array_search( "%$taxonomy%", $rewrite_tags_after, true ) );
+		$this->assertContains( "%$taxonomy%", $rewrite_tags );
+		$this->assertNotContains( "%$taxonomy%", $rewrite_tags_after );
 	}
 
 	public function test_adds_ajax_callback() {
diff --git a/tests/phpunit/tests/theme.php b/tests/phpunit/tests/theme.php
index aa67f7189c64d..e3b16212650de 100644
--- a/tests/phpunit/tests/theme.php
+++ b/tests/phpunit/tests/theme.php
@@ -457,7 +457,7 @@ public function test_switch_theme() {
 				$this->assertSame( $theme['Stylesheet'], get_stylesheet() );
 
 				$root_fs = $theme->get_theme_root();
-				$this->assertTrue( is_dir( $root_fs ) );
+				$this->assertDirectoryExists( $root_fs );
 
 				$root_uri = $theme->get_theme_root_uri();
 				$this->assertNotEmpty( $root_uri );