diff --git a/tests/phpunit/tests/actions.php b/tests/phpunit/tests/actions.php
index 51225f12dd..1db3fd463f 100644
--- a/tests/phpunit/tests/actions.php
+++ b/tests/phpunit/tests/actions.php
@@ -240,8 +240,8 @@ class Tests_Actions extends WP_UnitTestCase {
 		$this->assertSame( 1, did_action( $tag1 ) );
 		$this->assertSame( 0, did_action( $tag2 ) );
 
-		// Do action $tag2 a random number of times.
-		$count = rand( 0, 10 );
+		// Do action $tag2 10 times.
+		$count = 10;
 		for ( $i = 0; $i < $count; $i++ ) {
 			do_action( $tag2 );
 		}
diff --git a/tests/phpunit/tests/admin/includesPlugin.php b/tests/phpunit/tests/admin/includesPlugin.php
index 9a3b4e5cd9..2fde9195fd 100644
--- a/tests/phpunit/tests/admin/includesPlugin.php
+++ b/tests/phpunit/tests/admin/includesPlugin.php
@@ -487,11 +487,12 @@ class Tests_Admin_IncludesPlugin extends WP_UnitTestCase {
 		$p2 = $this->_create_plugin( "<?php\n//Test", 'not-a-dropin.php', WP_CONTENT_DIR );
 
 		$dropins = get_dropins();
-		$this->assertSame( array( 'advanced-cache.php' ), array_keys( $dropins ) );
 
 		unlink( $p1[1] );
 		unlink( $p2[1] );
 
+		$this->assertSame( array( 'advanced-cache.php' ), array_keys( $dropins ) );
+
 		// Clean up.
 		$this->_restore_drop_ins();
 	}
@@ -509,9 +510,11 @@ class Tests_Admin_IncludesPlugin extends WP_UnitTestCase {
 	public function test_is_network_only_plugin() {
 		$p = $this->_create_plugin( "<?php\n/*\nPlugin Name: test\nNetwork: true" );
 
-		$this->assertTrue( is_network_only_plugin( $p[0] ) );
+		$network_only = is_network_only_plugin( $p[0] );
 
 		unlink( $p[1] );
+
+		$this->assertTrue( $network_only );
 	}
 
 	/**
@@ -571,12 +574,14 @@ class Tests_Admin_IncludesPlugin extends WP_UnitTestCase {
 		$uninstallable_plugins[ $plugin[0] ] = true;
 		update_option( 'uninstall_plugins', $uninstallable_plugins );
 
-		$this->assertTrue( is_uninstallable_plugin( $plugin[0] ) );
+		$is_uninstallable = is_uninstallable_plugin( $plugin[0] );
 
 		unset( $uninstallable_plugins[ $plugin[0] ] );
 		update_option( 'uninstall_plugins', $uninstallable_plugins );
 
 		unlink( $plugin[1] );
+
+		$this->assertTrue( $is_uninstallable );
 	}
 
 	/**
@@ -595,14 +600,15 @@ class Tests_Admin_IncludesPlugin extends WP_UnitTestCase {
 	 */
 	private function _create_plugin( $data = "<?php\n/*\nPlugin Name: Test\n*/", $filename = false, $dir_path = false ) {
 		if ( false === $filename ) {
-			$filename = rand_str() . '.php';
+			$filename = __FUNCTION__ . '.php';
 		}
 
 		if ( false === $dir_path ) {
 			$dir_path = WP_PLUGIN_DIR;
 		}
 
-		$full_name = $dir_path . '/' . wp_unique_filename( $dir_path, $filename );
+		$filename  = wp_unique_filename( $dir_path, $filename );
+		$full_name = $dir_path . '/' . $filename;
 
 		$file = fopen( $full_name, 'w' );
 		fwrite( $file, $data );
diff --git a/tests/phpunit/tests/cron.php b/tests/phpunit/tests/cron.php
index 36d5edd7dd..04665b000e 100644
--- a/tests/phpunit/tests/cron.php
+++ b/tests/phpunit/tests/cron.php
@@ -270,7 +270,7 @@ class Tests_Cron extends WP_UnitTestCase {
 	 */
 	public function test_unschedule_hook() {
 		$hook = __FUNCTION__;
-		$args = array( rand_str() );
+		$args = array( 'foo' );
 
 		// Schedule several events with and without arguments.
 		wp_schedule_single_event( strtotime( '+1 hour' ), $hook );
diff --git a/tests/phpunit/tests/date/xmlrpc.php b/tests/phpunit/tests/date/xmlrpc.php
index 8f8fb2859d..8a4efaf46d 100644
--- a/tests/phpunit/tests/date/xmlrpc.php
+++ b/tests/phpunit/tests/date/xmlrpc.php
@@ -228,7 +228,7 @@ class Tests_Date_XMLRPC extends WP_XMLRPC_UnitTestCase {
 			'comment_author'       => 'Test commenter',
 			'comment_author_url'   => 'http://example.com/',
 			'comment_author_email' => 'example@example.com',
-			'comment_content'      => rand_str( 100 ),
+			'comment_content'      => 'Hello, world!',
 			'comment_approved'     => '1',
 		);
 		$comment_id   = wp_insert_comment( $comment_data );
diff --git a/tests/phpunit/tests/file.php b/tests/phpunit/tests/file.php
index eb6168d9af..311ba30339 100644
--- a/tests/phpunit/tests/file.php
+++ b/tests/phpunit/tests/file.php
@@ -96,8 +96,8 @@ class Tests_File extends WP_UnitTestCase {
 			return false;
 		}
 
-		// Write some random contents.
-		$c = rand_str();
+		// Write some contents.
+		$c = 'foo';
 		fwrite( $fp, $c );
 		fclose( $fp );
 
diff --git a/tests/phpunit/tests/hooks/addFilter.php b/tests/phpunit/tests/hooks/addFilter.php
index 5890f22044..593ba509b8 100644
--- a/tests/phpunit/tests/hooks/addFilter.php
+++ b/tests/phpunit/tests/hooks/addFilter.php
@@ -15,8 +15,8 @@ class Tests_Hooks_AddFilter extends WP_UnitTestCase {
 		$callback      = '__return_null';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 
@@ -30,8 +30,8 @@ class Tests_Hooks_AddFilter extends WP_UnitTestCase {
 		$callback      = array( $a, 'action' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 
@@ -44,8 +44,8 @@ class Tests_Hooks_AddFilter extends WP_UnitTestCase {
 		$callback      = array( 'MockAction', 'action' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 
@@ -59,8 +59,8 @@ class Tests_Hooks_AddFilter extends WP_UnitTestCase {
 		$callback_two  = '__return_false';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback_one, $priority, $accepted_args );
 		$this->assertCount( 1, $hook->callbacks[ $priority ] );
@@ -74,8 +74,8 @@ class Tests_Hooks_AddFilter extends WP_UnitTestCase {
 		$callback_two  = '__return_false';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback_one, $priority, $accepted_args );
 		$this->assertCount( 1, $hook->callbacks[ $priority ] );
@@ -89,8 +89,8 @@ class Tests_Hooks_AddFilter extends WP_UnitTestCase {
 		$callback      = '__return_null';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 		$this->assertCount( 1, $hook->callbacks[ $priority ] );
@@ -103,8 +103,8 @@ class Tests_Hooks_AddFilter extends WP_UnitTestCase {
 		$callback      = '__return_null';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 		$this->assertCount( 1, $hook->callbacks[ $priority ] );
diff --git a/tests/phpunit/tests/hooks/applyFilters.php b/tests/phpunit/tests/hooks/applyFilters.php
index fcb8e3b126..388f85c5c2 100644
--- a/tests/phpunit/tests/hooks/applyFilters.php
+++ b/tests/phpunit/tests/hooks/applyFilters.php
@@ -13,8 +13,8 @@ class Tests_Hooks_ApplyFilters extends WP_UnitTestCase {
 		$callback      = array( $a, 'filter' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 		$arg           = __FUNCTION__ . '_arg';
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
@@ -30,8 +30,8 @@ class Tests_Hooks_ApplyFilters extends WP_UnitTestCase {
 		$callback      = array( $a, 'filter' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 		$arg           = __FUNCTION__ . '_arg';
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
diff --git a/tests/phpunit/tests/hooks/doAction.php b/tests/phpunit/tests/hooks/doAction.php
index 0fb5652f3b..5ac1d4d4b9 100644
--- a/tests/phpunit/tests/hooks/doAction.php
+++ b/tests/phpunit/tests/hooks/doAction.php
@@ -21,8 +21,8 @@ class Tests_Hooks_DoAction extends WP_UnitTestCase {
 		$callback      = array( $a, 'action' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 		$arg           = __FUNCTION__ . '_arg';
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
@@ -36,8 +36,8 @@ class Tests_Hooks_DoAction extends WP_UnitTestCase {
 		$callback      = array( $a, 'filter' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 		$arg           = __FUNCTION__ . '_arg';
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
@@ -54,8 +54,8 @@ class Tests_Hooks_DoAction extends WP_UnitTestCase {
 		$callback_two  = array( $b, 'filter' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 		$arg           = __FUNCTION__ . '_arg';
 
 		$hook->add_filter( $tag, $callback_one, $priority, $accepted_args );
@@ -73,8 +73,8 @@ class Tests_Hooks_DoAction extends WP_UnitTestCase {
 		$callback_two  = array( $b, 'filter' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 		$arg           = __FUNCTION__ . '_arg';
 
 		$hook->add_filter( $tag, $callback_one, $priority, $accepted_args );
@@ -89,7 +89,7 @@ class Tests_Hooks_DoAction extends WP_UnitTestCase {
 		$callback      = array( $this, '_action_callback' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
+		$priority      = 1;
 		$accepted_args = 0;
 		$arg           = __FUNCTION__ . '_arg';
 
@@ -103,7 +103,7 @@ class Tests_Hooks_DoAction extends WP_UnitTestCase {
 		$callback      = array( $this, '_action_callback' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
+		$priority      = 1;
 		$accepted_args = 1;
 		$arg           = __FUNCTION__ . '_arg';
 
@@ -117,7 +117,7 @@ class Tests_Hooks_DoAction extends WP_UnitTestCase {
 		$callback      = array( $this, '_action_callback' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
+		$priority      = 100;
 		$accepted_args = 1000;
 		$arg           = __FUNCTION__ . '_arg';
 
diff --git a/tests/phpunit/tests/hooks/doAllHook.php b/tests/phpunit/tests/hooks/doAllHook.php
index 29eec96428..776c3e4576 100644
--- a/tests/phpunit/tests/hooks/doAllHook.php
+++ b/tests/phpunit/tests/hooks/doAllHook.php
@@ -13,8 +13,8 @@ class Tests_Hooks_DoAllHook extends WP_UnitTestCase {
 		$callback      = array( $a, 'action' );
 		$hook          = new WP_Hook();
 		$tag           = 'all';
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 		$arg           = 'all_arg';
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
diff --git a/tests/phpunit/tests/hooks/hasFilter.php b/tests/phpunit/tests/hooks/hasFilter.php
index f9d48b3d4e..f6dde3a0f8 100644
--- a/tests/phpunit/tests/hooks/hasFilter.php
+++ b/tests/phpunit/tests/hooks/hasFilter.php
@@ -12,8 +12,8 @@ class Tests_Hooks_HasFilter extends WP_UnitTestCase {
 		$callback      = '__return_null';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 
@@ -25,8 +25,8 @@ class Tests_Hooks_HasFilter extends WP_UnitTestCase {
 		$callback      = array( $a, 'action' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 
@@ -37,8 +37,8 @@ class Tests_Hooks_HasFilter extends WP_UnitTestCase {
 		$callback      = array( 'MockAction', 'action' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 
@@ -49,8 +49,8 @@ class Tests_Hooks_HasFilter extends WP_UnitTestCase {
 		$callback      = '__return_null';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 
@@ -74,8 +74,8 @@ class Tests_Hooks_HasFilter extends WP_UnitTestCase {
 		$callback      = '__return_null';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 
diff --git a/tests/phpunit/tests/hooks/hasFilters.php b/tests/phpunit/tests/hooks/hasFilters.php
index f5c1e657fc..068ec88e52 100644
--- a/tests/phpunit/tests/hooks/hasFilters.php
+++ b/tests/phpunit/tests/hooks/hasFilters.php
@@ -12,8 +12,8 @@ class Tests_Hooks_HasFilters extends WP_UnitTestCase {
 		$callback      = '__return_null';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 
@@ -29,8 +29,8 @@ class Tests_Hooks_HasFilters extends WP_UnitTestCase {
 		$callback      = '__return_null';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 		$hook->remove_filter( $tag, $callback, $priority );
@@ -41,8 +41,8 @@ class Tests_Hooks_HasFilters extends WP_UnitTestCase {
 		$callback      = '__return_null';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 		$function_key = _wp_filter_build_unique_id( $tag, $callback, $priority );
diff --git a/tests/phpunit/tests/hooks/iterator.php b/tests/phpunit/tests/hooks/iterator.php
index 4840aa3d4d..0bfdcab36b 100644
--- a/tests/phpunit/tests/hooks/iterator.php
+++ b/tests/phpunit/tests/hooks/iterator.php
@@ -13,8 +13,8 @@ class Tests_Hooks_Iterator extends WP_UnitTestCase {
 		$callback_two  = '__return_false';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback_one, $priority, $accepted_args );
 		$hook->add_filter( $tag, $callback_two, $priority + 1, $accepted_args );
diff --git a/tests/phpunit/tests/hooks/preinitHooks.php b/tests/phpunit/tests/hooks/preinitHooks.php
index 551d64400f..18afaf6992 100644
--- a/tests/phpunit/tests/hooks/preinitHooks.php
+++ b/tests/phpunit/tests/hooks/preinitHooks.php
@@ -10,9 +10,9 @@ class Tests_Hooks_PreinitHooks extends WP_UnitTestCase {
 
 	public function test_array_to_hooks() {
 		$tag1      = __FUNCTION__ . '_1';
-		$priority1 = rand( 1, 100 );
+		$priority1 = 1;
 		$tag2      = __FUNCTION__ . '_2';
-		$priority2 = rand( 1, 100 );
+		$priority2 = 2;
 		$filters   = array(
 			$tag1 => array(
 				$priority1 => array(
diff --git a/tests/phpunit/tests/hooks/removeAllFilters.php b/tests/phpunit/tests/hooks/removeAllFilters.php
index cfaf81f4c8..90b8a06cda 100644
--- a/tests/phpunit/tests/hooks/removeAllFilters.php
+++ b/tests/phpunit/tests/hooks/removeAllFilters.php
@@ -12,8 +12,8 @@ class Tests_Hooks_RemoveAllFilters extends WP_UnitTestCase {
 		$callback      = '__return_null';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 
@@ -27,8 +27,8 @@ class Tests_Hooks_RemoveAllFilters extends WP_UnitTestCase {
 		$callback_two  = '__return_false';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback_one, $priority, $accepted_args );
 		$hook->add_filter( $tag, $callback_two, $priority + 1, $accepted_args );
diff --git a/tests/phpunit/tests/hooks/removeFilter.php b/tests/phpunit/tests/hooks/removeFilter.php
index 793cd02b3c..adf8b6ad75 100644
--- a/tests/phpunit/tests/hooks/removeFilter.php
+++ b/tests/phpunit/tests/hooks/removeFilter.php
@@ -12,8 +12,8 @@ class Tests_Hooks_RemoveFilter extends WP_UnitTestCase {
 		$callback      = '__return_null';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 		$hook->remove_filter( $tag, $callback, $priority );
@@ -26,8 +26,8 @@ class Tests_Hooks_RemoveFilter extends WP_UnitTestCase {
 		$callback      = array( $a, 'action' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 		$hook->remove_filter( $tag, $callback, $priority );
@@ -39,8 +39,8 @@ class Tests_Hooks_RemoveFilter extends WP_UnitTestCase {
 		$callback      = array( 'MockAction', 'action' );
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback, $priority, $accepted_args );
 		$hook->remove_filter( $tag, $callback, $priority );
@@ -53,8 +53,8 @@ class Tests_Hooks_RemoveFilter extends WP_UnitTestCase {
 		$callback_two  = '__return_false';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback_one, $priority, $accepted_args );
 		$hook->add_filter( $tag, $callback_two, $priority, $accepted_args );
@@ -69,8 +69,8 @@ class Tests_Hooks_RemoveFilter extends WP_UnitTestCase {
 		$callback_two  = '__return_false';
 		$hook          = new WP_Hook();
 		$tag           = __FUNCTION__;
-		$priority      = rand( 1, 100 );
-		$accepted_args = rand( 1, 100 );
+		$priority      = 1;
+		$accepted_args = 2;
 
 		$hook->add_filter( $tag, $callback_one, $priority, $accepted_args );
 		$hook->add_filter( $tag, $callback_two, $priority + 1, $accepted_args );
diff --git a/tests/phpunit/tests/image/intermediateSize.php b/tests/phpunit/tests/image/intermediateSize.php
index b67e795163..830359427a 100644
--- a/tests/phpunit/tests/image/intermediateSize.php
+++ b/tests/phpunit/tests/image/intermediateSize.php
@@ -181,23 +181,23 @@ class Tests_Image_Intermediate_Size extends WP_UnitTestCase {
 	 * @requires function imagejpeg
 	 */
 	public function test_get_intermediate_sizes_by_array_zero_height() {
-		// Generate random width.
-		$random_w = rand( 300, 400 );
+		// Use this width.
+		$width = 300;
 
 		// Only one dimention match shouldn't return false positive (see: #17626).
-		add_image_size( 'test-size', $random_w, 0, false );
-		add_image_size( 'false-height', $random_w, 100, true );
+		add_image_size( 'test-size', $width, 0, false );
+		add_image_size( 'false-height', $width, 100, true );
 
 		$file = DIR_TESTDATA . '/images/waffles.jpg';
 		$id   = $this->_make_attachment( $file, 0 );
 
 		$original = wp_get_attachment_metadata( $id );
-		$image_w  = $random_w;
+		$image_w  = $width;
 		$image_h  = round( ( $image_w / $original['width'] ) * $original['height'] );
 
 		// Look for a size by array that exists.
 		// Note: Staying larger than 300px to miss default medium crop.
-		$image = image_get_intermediate_size( $id, array( $random_w, 0 ) );
+		$image = image_get_intermediate_size( $id, array( $width, 0 ) );
 
 		// Test for the expected string because the array will by definition
 		// return with the correct height and width attributes.
diff --git a/tests/phpunit/tests/post.php b/tests/phpunit/tests/post.php
index f8edf13dae..c7d60f4b5f 100644
--- a/tests/phpunit/tests/post.php
+++ b/tests/phpunit/tests/post.php
@@ -68,8 +68,8 @@ class Tests_Post extends WP_UnitTestCase {
 			$post = array(
 				'post_author'  => self::$editor_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
-				'post_title'   => rand_str(),
+				'post_content' => "{$post_type}_content",
+				'post_title'   => "{$post_type}_title",
 				'tax_input'    => array(
 					'post_tag' => 'tag1,tag2',
 					'ctax'     => 'cterm1,cterm2',
@@ -126,8 +126,8 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = array(
 			'post_author'  => self::$editor_id,
 			'post_status'  => 'publish',
-			'post_content' => rand_str(),
-			'post_title'   => rand_str(),
+			'post_content' => 'content',
+			'post_title'   => 'title',
 			'post_date'    => date_format( date_create( "@{$future_date}" ), 'Y-m-d H:i:s' ),
 		);
 
@@ -162,8 +162,8 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = array(
 			'post_author'  => self::$editor_id,
 			'post_status'  => 'publish',
-			'post_content' => rand_str(),
-			'post_title'   => rand_str(),
+			'post_content' => 'content',
+			'post_title'   => 'title',
 			'post_date'    => date_format( date_create( "@{$future_date_1}" ), 'Y-m-d H:i:s' ),
 		);
 
@@ -207,8 +207,8 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = array(
 			'post_author'  => self::$editor_id,
 			'post_status'  => 'publish',
-			'post_content' => rand_str(),
-			'post_title'   => rand_str(),
+			'post_content' => 'content',
+			'post_title'   => 'title',
 			'post_date'    => date_format( date_create( "@{$future_date_1}" ), 'Y-m-d H:i:s' ),
 		);
 
@@ -249,8 +249,8 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = array(
 			'post_author'  => self::$editor_id,
 			'post_status'  => 'draft',
-			'post_content' => rand_str(),
-			'post_title'   => rand_str(),
+			'post_content' => 'content',
+			'post_title'   => 'title',
 			'post_date'    => date_format( date_create( "@{$future_date}" ), 'Y-m-d H:i:s' ),
 		);
 
@@ -284,8 +284,8 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = array(
 			'post_author'  => self::$editor_id,
 			'post_status'  => 'publish',
-			'post_content' => rand_str(),
-			'post_title'   => rand_str(),
+			'post_content' => 'content',
+			'post_title'   => 'title',
 			'post_date'    => date_format( date_create( "@{$future_date_1}" ), 'Y-m-d H:i:s' ),
 		);
 
@@ -328,8 +328,8 @@ class Tests_Post extends WP_UnitTestCase {
 			$post = array(
 				'post_author'  => self::$editor_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
-				'post_title'   => rand_str(),
+				'post_content' => "{$status}_content",
+				'post_title'   => "{$status}_title",
 				'post_date'    => date_format( date_create( "@{$future_date_1}" ), 'Y-m-d H:i:s' ),
 			);
 
@@ -370,8 +370,8 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = array(
 			'post_author'  => self::$editor_id,
 			'post_status'  => 'private',
-			'post_content' => rand_str(),
-			'post_title'   => rand_str(),
+			'post_content' => 'content',
+			'post_title'   => 'title',
 			'post_date'    => date_format( date_create( "@{$future_date}" ), 'Y-m-d H:i:s' ),
 		);
 
@@ -404,8 +404,8 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = array(
 			'post_author'  => self::$editor_id,
 			'post_status'  => 'publish',
-			'post_content' => rand_str(),
-			'post_title'   => rand_str(),
+			'post_content' => 'content',
+			'post_title'   => 'title',
 			'post_date'    => '2012-02-30 00:00:00',
 		);
 
@@ -427,8 +427,8 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = array(
 			'post_author'  => self::$editor_id,
 			'post_status'  => 'publish',
-			'post_content' => rand_str(),
-			'post_title'   => rand_str(),
+			'post_content' => 'content',
+			'post_title'   => 'title',
 			'post_date'    => date_format( date_create( "@{$future_date_1}" ), 'Y-m-d H:i:s' ),
 		);
 
@@ -533,8 +533,8 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = array(
 			'post_author'  => self::$editor_id,
 			'post_status'  => 'publish',
-			'post_content' => rand_str(),
-			'post_title'   => rand_str(),
+			'post_content' => 'content',
+			'post_title'   => 'title',
 			'post_date'    => date_format( date_create( "@{$future_date}" ), 'Y-m-d H:i:s' ),
 		);
 
@@ -564,7 +564,7 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = array(
 			'post_author'  => self::$editor_id,
 			'post_status'  => 'publish',
-			'post_content' => rand_str(),
+			'post_content' => 'content',
 			'post_title'   => '',
 			'post_date'    => '2007-10-31 06:15:00',
 		);
@@ -782,11 +782,11 @@ class Tests_Post extends WP_UnitTestCase {
 
 		register_taxonomy( 'test_tax', 'post' );
 
-		$title          = rand_str();
+		$title          = 'title';
 		$post_data      = array(
 			'post_author'  => self::$editor_id,
 			'post_status'  => 'publish',
-			'post_content' => rand_str(),
+			'post_content' => 'content',
 			'post_title'   => $title,
 			'tax_input'    => array(
 				'test_tax' => array( 'term', 'term2', 'term3' ),
@@ -906,7 +906,7 @@ class Tests_Post extends WP_UnitTestCase {
 		register_taxonomy( $tax, $post_type );
 
 		$post = self::factory()->post->create( array( 'post_type' => $post_type ) );
-		wp_set_object_terms( $post, rand_str(), $tax );
+		wp_set_object_terms( $post, 'foo', $tax );
 
 		$wp_tag_cloud = wp_tag_cloud(
 			array(
@@ -973,8 +973,8 @@ class Tests_Post extends WP_UnitTestCase {
 			array(
 				'post_author'  => self::$editor_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
-				'post_title'   => rand_str(),
+				'post_content' => 'content',
+				'post_title'   => 'title',
 			)
 		);
 		$post    = get_post( $post_id );
@@ -991,8 +991,8 @@ class Tests_Post extends WP_UnitTestCase {
 			array(
 				'post_author'  => self::$editor_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
-				'post_title'   => rand_str(),
+				'post_content' => 'content',
+				'post_title'   => 'title',
 				'post_type'    => 'page',
 			)
 		);
@@ -1203,8 +1203,8 @@ class Tests_Post extends WP_UnitTestCase {
 		$post = array(
 			'post_author'   => self::$editor_id,
 			'post_status'   => 'publish',
-			'post_content'  => rand_str(),
-			'post_title'    => rand_str(),
+			'post_content'  => 'content',
+			'post_title'    => 'title',
 			'post_date_gmt' => '2014-01-01 12:00:00',
 		);
 
diff --git a/tests/phpunit/tests/post/attachments.php b/tests/phpunit/tests/post/attachments.php
index 86b24cfd32..2922c185d2 100644
--- a/tests/phpunit/tests/post/attachments.php
+++ b/tests/phpunit/tests/post/attachments.php
@@ -272,8 +272,8 @@ class Tests_Post_Attachments extends WP_UnitTestCase {
 
 		$post_id = wp_insert_post(
 			array(
-				'post_content' => rand_str(),
-				'post_title'   => rand_str(),
+				'post_content' => 'content',
+				'post_title'   => 'title',
 			)
 		);
 
diff --git a/tests/phpunit/tests/post/meta.php b/tests/phpunit/tests/post/meta.php
index 37c07d84e8..ad391e741f 100644
--- a/tests/phpunit/tests/post/meta.php
+++ b/tests/phpunit/tests/post/meta.php
@@ -23,8 +23,8 @@ class Tests_Post_Meta extends WP_UnitTestCase {
 			array(
 				'post_author'  => self::$author->ID,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
-				'post_title'   => rand_str(),
+				'post_content' => 'content',
+				'post_title'   => 'title',
 			)
 		);
 
@@ -32,8 +32,8 @@ class Tests_Post_Meta extends WP_UnitTestCase {
 			array(
 				'post_author'  => self::$author->ID,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
-				'post_title'   => rand_str(),
+				'post_content' => 'content',
+				'post_title'   => 'title',
 			)
 		);
 	}
diff --git a/tests/phpunit/tests/post/nav-menu.php b/tests/phpunit/tests/post/nav-menu.php
index 36c7785f6e..c95c6709c4 100644
--- a/tests/phpunit/tests/post/nav-menu.php
+++ b/tests/phpunit/tests/post/nav-menu.php
@@ -12,7 +12,7 @@ class Tests_Post_Nav_Menu extends WP_UnitTestCase {
 	public function set_up() {
 		parent::set_up();
 
-		$this->menu_id = wp_create_nav_menu( rand_str() );
+		$this->menu_id = wp_create_nav_menu( 'foo' );
 	}
 
 	/**
@@ -255,8 +255,8 @@ class Tests_Post_Nav_Menu extends WP_UnitTestCase {
 	 */
 	public function test_wp_setup_nav_menu_item_for_post_type_archive() {
 
-		$post_type_slug        = rand_str( 12 );
-		$post_type_description = rand_str();
+		$post_type_slug        = 'fooo-bar-baz';
+		$post_type_description = 'foo';
 		register_post_type(
 			$post_type_slug,
 			array(
@@ -288,7 +288,7 @@ class Tests_Post_Nav_Menu extends WP_UnitTestCase {
 	 */
 	public function test_wp_setup_nav_menu_item_for_post_type_archive_no_description() {
 
-		$post_type_slug        = rand_str( 12 );
+		$post_type_slug        = 'fooo-bar-baz';
 		$post_type_description = '';
 		register_post_type(
 			$post_type_slug,
@@ -319,8 +319,8 @@ class Tests_Post_Nav_Menu extends WP_UnitTestCase {
 	 */
 	public function test_wp_setup_nav_menu_item_for_post_type_archive_custom_description() {
 
-		$post_type_slug        = rand_str( 12 );
-		$post_type_description = rand_str();
+		$post_type_slug        = 'fooo-bar-baz';
+		$post_type_description = 'foobaz';
 		register_post_type(
 			$post_type_slug,
 			array(
@@ -331,7 +331,7 @@ class Tests_Post_Nav_Menu extends WP_UnitTestCase {
 			)
 		);
 
-		$menu_item_description = rand_str();
+		$menu_item_description = 'foo_description';
 
 		$post_type_archive_item_id = wp_update_nav_menu_item(
 			$this->menu_id,
@@ -354,7 +354,7 @@ class Tests_Post_Nav_Menu extends WP_UnitTestCase {
 	 */
 	public function test_wp_setup_nav_menu_item_for_unknown_post_type_archive_no_description() {
 
-		$post_type_slug = rand_str( 12 );
+		$post_type_slug = 'fooo-bar-baz';
 
 		$post_type_archive_item_id = wp_update_nav_menu_item(
 			$this->menu_id,
diff --git a/tests/phpunit/tests/post/query.php b/tests/phpunit/tests/post/query.php
index 29267e429a..e7def81a0c 100644
--- a/tests/phpunit/tests/post/query.php
+++ b/tests/phpunit/tests/post/query.php
@@ -132,33 +132,33 @@ class Tests_Post_Query extends WP_UnitTestCase {
 		$post_id1 = self::factory()->post->create(
 			array(
 				'post_type'  => 'page',
-				'menu_order' => rand( 1, 100 ),
+				'menu_order' => 1,
 			)
 		);
 		$post_id2 = self::factory()->post->create(
 			array(
 				'post_type'  => 'page',
-				'menu_order' => rand( 1, 100 ),
+				'menu_order' => 2,
 			)
 		);
 		$post_id3 = self::factory()->post->create(
 			array(
 				'post_type'   => 'page',
 				'post_parent' => $post_id2,
-				'menu_order'  => rand( 1, 100 ),
+				'menu_order'  => 3,
 			)
 		);
 		$post_id4 = self::factory()->post->create(
 			array(
 				'post_type'   => 'page',
 				'post_parent' => $post_id2,
-				'menu_order'  => rand( 1, 100 ),
+				'menu_order'  => 4,
 			)
 		);
 		$post_id5 = self::factory()->post->create(
 			array(
 				'post_type'  => 'page',
-				'menu_order' => rand( 1, 100 ),
+				'menu_order' => 5,
 			)
 		);
 
@@ -219,7 +219,7 @@ class Tests_Post_Query extends WP_UnitTestCase {
 			$post_id,
 			array(
 				'post_mime_type' => 'image/jpeg',
-				'menu_order'     => rand( 1, 100 ),
+				'menu_order'     => 1,
 			)
 		);
 		$att_ids[2] = self::factory()->attachment->create_object(
@@ -227,7 +227,7 @@ class Tests_Post_Query extends WP_UnitTestCase {
 			$post_id,
 			array(
 				'post_mime_type' => 'image/jpeg',
-				'menu_order'     => rand( 1, 100 ),
+				'menu_order'     => 2,
 			)
 		);
 		$att_ids[3] = self::factory()->attachment->create_object(
@@ -235,7 +235,7 @@ class Tests_Post_Query extends WP_UnitTestCase {
 			$post_id,
 			array(
 				'post_mime_type' => 'image/jpeg',
-				'menu_order'     => rand( 1, 100 ),
+				'menu_order'     => 3,
 			)
 		);
 		$att_ids[4] = self::factory()->attachment->create_object(
@@ -243,7 +243,7 @@ class Tests_Post_Query extends WP_UnitTestCase {
 			$post_id,
 			array(
 				'post_mime_type' => 'image/jpeg',
-				'menu_order'     => rand( 1, 100 ),
+				'menu_order'     => 4,
 			)
 		);
 		$att_ids[5] = self::factory()->attachment->create_object(
@@ -251,7 +251,7 @@ class Tests_Post_Query extends WP_UnitTestCase {
 			$post_id,
 			array(
 				'post_mime_type' => 'image/jpeg',
-				'menu_order'     => rand( 1, 100 ),
+				'menu_order'     => 5,
 			)
 		);
 
diff --git a/tests/phpunit/tests/post/revisions.php b/tests/phpunit/tests/post/revisions.php
index 4ff458a012..322114e474 100644
--- a/tests/phpunit/tests/post/revisions.php
+++ b/tests/phpunit/tests/post/revisions.php
@@ -17,7 +17,7 @@ class Tests_Post_Revisions extends WP_UnitTestCase {
 
 	public function set_up() {
 		parent::set_up();
-		$this->post_type = rand_str( 20 );
+		$this->post_type = 'test-revision';
 	}
 
 	/**
@@ -446,7 +446,7 @@ class Tests_Post_Revisions extends WP_UnitTestCase {
 			array(
 				'post_status'  => 'publish',
 				'ID'           => $post_id,
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 			)
 		);
 
diff --git a/tests/phpunit/tests/post/types.php b/tests/phpunit/tests/post/types.php
index 449467cf1d..7bba3b639b 100644
--- a/tests/phpunit/tests/post/types.php
+++ b/tests/phpunit/tests/post/types.php
@@ -21,7 +21,7 @@ class Tests_Post_Types extends WP_UnitTestCase {
 	public function set_up() {
 		parent::set_up();
 
-		$this->post_type = rand_str( 20 );
+		$this->post_type = 'foo1';
 	}
 
 	public function test_register_post_type() {
diff --git a/tests/phpunit/tests/query/commentCount.php b/tests/phpunit/tests/query/commentCount.php
index 4f7803dd6b..5a759a3f06 100644
--- a/tests/phpunit/tests/query/commentCount.php
+++ b/tests/phpunit/tests/query/commentCount.php
@@ -21,7 +21,7 @@ class Tests_Query_CommentCount extends WP_UnitTestCase {
 	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
 		$post_id             = $factory->post->create(
 			array(
-				'post_content' => 1 . rand_str() . ' about',
+				'post_content' => '1 about',
 				'post_type'    => self::$post_type,
 			)
 		);
@@ -30,7 +30,7 @@ class Tests_Query_CommentCount extends WP_UnitTestCase {
 
 		$post_id             = $factory->post->create(
 			array(
-				'post_content' => 1 . rand_str() . ' about',
+				'post_content' => '2 about',
 				'post_type'    => self::$post_type,
 			)
 		);
@@ -41,7 +41,7 @@ class Tests_Query_CommentCount extends WP_UnitTestCase {
 
 		$post_id             = $factory->post->create(
 			array(
-				'post_content' => 1 . rand_str() . ' about',
+				'post_content' => '3 about',
 				'post_type'    => self::$post_type,
 			)
 		);
@@ -52,7 +52,7 @@ class Tests_Query_CommentCount extends WP_UnitTestCase {
 
 		$post_id             = $factory->post->create(
 			array(
-				'post_content' => 1 . rand_str() . ' about',
+				'post_content' => '4 about',
 				'post_type'    => self::$post_type,
 			)
 		);
diff --git a/tests/phpunit/tests/query/search.php b/tests/phpunit/tests/query/search.php
index 2beda65d2f..418acbfc85 100644
--- a/tests/phpunit/tests/query/search.php
+++ b/tests/phpunit/tests/query/search.php
@@ -10,7 +10,7 @@ class Tests_Query_Search extends WP_UnitTestCase {
 	public function set_up() {
 		parent::set_up();
 
-		$this->post_type = rand_str( 12 );
+		$this->post_type = 'foo1';
 		register_post_type( $this->post_type );
 
 		$this->q = new WP_Query();
@@ -36,7 +36,7 @@ class Tests_Query_Search extends WP_UnitTestCase {
 		foreach ( range( 1, 7 ) as $i ) {
 			self::factory()->post->create(
 				array(
-					'post_content' => $i . rand_str() . ' about',
+					'post_content' => "{$i} about",
 					'post_type'    => $this->post_type,
 				)
 			);
diff --git a/tests/phpunit/tests/query/taxQuery.php b/tests/phpunit/tests/query/taxQuery.php
index 2ca00b605b..2094262e24 100644
--- a/tests/phpunit/tests/query/taxQuery.php
+++ b/tests/phpunit/tests/query/taxQuery.php
@@ -1209,8 +1209,8 @@ class Tests_Query_TaxQuery extends WP_UnitTestCase {
 		register_taxonomy_for_object_type( 'post_tag', 'attachment:image' );
 		$tag_id   = self::factory()->term->create(
 			array(
-				'slug' => rand_str(),
-				'name' => rand_str(),
+				'slug' => 'foo-bar',
+				'name' => 'Foo Bar',
 			)
 		);
 		$image_id = self::factory()->attachment->create_object(
diff --git a/tests/phpunit/tests/rest-api/rest-attachments-controller.php b/tests/phpunit/tests/rest-api/rest-attachments-controller.php
index fae3bbb8b3..47ea5820f3 100644
--- a/tests/phpunit/tests/rest-api/rest-attachments-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-attachments-controller.php
@@ -522,8 +522,8 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	public function test_get_items_invalid_date() {
 		$request = new WP_REST_Request( 'GET', '/wp/v2/media' );
-		$request->set_param( 'after', rand_str() );
-		$request->set_param( 'before', rand_str() );
+		$request->set_param( 'after', 'foo' );
+		$request->set_param( 'before', 'bar' );
 		$response = rest_get_server()->dispatch( $request );
 		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
 	}
@@ -570,8 +570,8 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 	 */
 	public function test_get_items_invalid_modified_date() {
 		$request = new WP_REST_Request( 'GET', '/wp/v2/media' );
-		$request->set_param( 'modified_after', rand_str() );
-		$request->set_param( 'modified_before', rand_str() );
+		$request->set_param( 'modified_after', 'foo' );
+		$request->set_param( 'modified_before', 'bar' );
 		$response = rest_get_server()->dispatch( $request );
 		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
 	}
diff --git a/tests/phpunit/tests/rest-api/rest-comments-controller.php b/tests/phpunit/tests/rest-api/rest-comments-controller.php
index 0c7ed625b7..99986a8037 100644
--- a/tests/phpunit/tests/rest-api/rest-comments-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-comments-controller.php
@@ -888,8 +888,8 @@ class WP_Test_REST_Comments_Controller extends WP_Test_REST_Controller_Testcase
 
 	public function test_get_comments_invalid_date() {
 		$request = new WP_REST_Request( 'GET', '/wp/v2/comments' );
-		$request->set_param( 'after', rand_str() );
-		$request->set_param( 'before', rand_str() );
+		$request->set_param( 'after', 'foo' );
+		$request->set_param( 'before', 'bar' );
 		$response = rest_get_server()->dispatch( $request );
 		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
 	}
@@ -1477,7 +1477,7 @@ class WP_Test_REST_Comments_Controller extends WP_Test_REST_Controller_Testcase
 			'author_email' => 'lovejoy@example.com',
 			'author_url'   => 'http://timothylovejoy.jr',
 			'content'      => 'It\'s all over\, people! We don\'t have a prayer!',
-			'date'         => rand_str(),
+			'date'         => 'foo-bar',
 		);
 
 		$request = new WP_REST_Request( 'POST', '/wp/v2/comments' );
@@ -2625,8 +2625,8 @@ class WP_Test_REST_Comments_Controller extends WP_Test_REST_Controller_Testcase
 		wp_set_current_user( self::$admin_id );
 
 		$params = array(
-			'content' => rand_str(),
-			'date'    => rand_str(),
+			'content' => 'content',
+			'date'    => 'foo',
 		);
 
 		$request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/comments/%d', self::$approved_id ) );
@@ -2641,8 +2641,8 @@ class WP_Test_REST_Comments_Controller extends WP_Test_REST_Controller_Testcase
 		wp_set_current_user( self::$admin_id );
 
 		$params = array(
-			'content'  => rand_str(),
-			'date_gmt' => rand_str(),
+			'content'  => 'content',
+			'date_gmt' => 'foo',
 		);
 
 		$request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/comments/%d', self::$approved_id ) );
@@ -2770,7 +2770,7 @@ class WP_Test_REST_Comments_Controller extends WP_Test_REST_Controller_Testcase
 		// Change the comment parent.
 		$request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/comments/%s', $child_comment ) );
 		$request->set_param( 'parent', $comment_id_1 );
-		$request->set_param( 'content', rand_str() );
+		$request->set_param( 'content', 'foo bar' );
 		$response = rest_get_server()->dispatch( $request );
 		$this->assertSame( 200, $response->get_status() );
 
diff --git a/tests/phpunit/tests/rest-api/rest-pages-controller.php b/tests/phpunit/tests/rest-api/rest-pages-controller.php
index f4548f3fc8..da24a13d9b 100644
--- a/tests/phpunit/tests/rest-api/rest-pages-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pages-controller.php
@@ -330,8 +330,8 @@ class WP_Test_REST_Pages_Controller extends WP_Test_REST_Post_Type_Controller_Te
 
 	public function test_get_items_invalid_date() {
 		$request = new WP_REST_Request( 'GET', '/wp/v2/pages' );
-		$request->set_param( 'after', rand_str() );
-		$request->set_param( 'before', rand_str() );
+		$request->set_param( 'after', 'foo' );
+		$request->set_param( 'before', 'bar' );
 		$response = rest_get_server()->dispatch( $request );
 		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
 	}
@@ -369,8 +369,8 @@ class WP_Test_REST_Pages_Controller extends WP_Test_REST_Post_Type_Controller_Te
 	 */
 	public function test_get_items_invalid_modified_date() {
 		$request = new WP_REST_Request( 'GET', '/wp/v2/pages' );
-		$request->set_param( 'modified_after', rand_str() );
-		$request->set_param( 'modified_before', rand_str() );
+		$request->set_param( 'modified_after', 'foo' );
+		$request->set_param( 'modified_before', 'bar' );
 		$response = rest_get_server()->dispatch( $request );
 		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
 	}
diff --git a/tests/phpunit/tests/rest-api/rest-posts-controller.php b/tests/phpunit/tests/rest-api/rest-posts-controller.php
index d820e86d74..f02037962c 100644
--- a/tests/phpunit/tests/rest-api/rest-posts-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-posts-controller.php
@@ -1694,8 +1694,8 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 
 	public function test_get_items_invalid_date() {
 		$request = new WP_REST_Request( 'GET', '/wp/v2/posts' );
-		$request->set_param( 'after', rand_str() );
-		$request->set_param( 'before', rand_str() );
+		$request->set_param( 'after', 'foo' );
+		$request->set_param( 'before', 'bar' );
 		$response = rest_get_server()->dispatch( $request );
 		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
 	}
@@ -1719,8 +1719,8 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 	 */
 	public function test_get_items_invalid_modified_date() {
 		$request = new WP_REST_Request( 'GET', '/wp/v2/posts' );
-		$request->set_param( 'modified_after', rand_str() );
-		$request->set_param( 'modified_before', rand_str() );
+		$request->set_param( 'modified_after', 'foo' );
+		$request->set_param( 'modified_before', 'bar' );
 		$response = rest_get_server()->dispatch( $request );
 		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
 	}
@@ -2697,7 +2697,7 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 			0,
 			array(
 				'post_mime_type' => 'image/jpeg',
-				'menu_order'     => rand( 1, 100 ),
+				'menu_order'     => 1,
 			)
 		);
 
@@ -3310,7 +3310,7 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 	public function test_update_post_ignore_readonly() {
 		wp_set_current_user( self::$editor_id );
 
-		$new_content       = rand_str();
+		$new_content       = 'foo bar baz';
 		$expected_modified = current_time( 'mysql' );
 
 		$request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/posts/%d', self::$post_id ) );
@@ -3375,7 +3375,7 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 		$request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/posts/%d', self::$post_id ) );
 		$params  = $this->set_post_data(
 			array(
-				'date' => rand_str(),
+				'date' => 'foo',
 			)
 		);
 		$request->set_body_params( $params );
@@ -3390,7 +3390,7 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 		$request = new WP_REST_Request( 'PUT', sprintf( '/wp/v2/posts/%d', self::$post_id ) );
 		$params  = $this->set_post_data(
 			array(
-				'date_gmt' => rand_str(),
+				'date_gmt' => 'foo',
 			)
 		);
 		$request->set_body_params( $params );
diff --git a/tests/phpunit/tests/rewrite.php b/tests/phpunit/tests/rewrite.php
index 62697800cc..1a5ad9774b 100644
--- a/tests/phpunit/tests/rewrite.php
+++ b/tests/phpunit/tests/rewrite.php
@@ -173,7 +173,7 @@ class Tests_Rewrite extends WP_UnitTestCase {
 	public function test_url_to_postid_custom_post_type() {
 		delete_option( 'rewrite_rules' );
 
-		$post_type = rand_str( 12 );
+		$post_type = 'url_to_postid';
 		register_post_type( $post_type, array( 'public' => true ) );
 
 		$id = self::factory()->post->create( array( 'post_type' => $post_type ) );
diff --git a/tests/phpunit/tests/rewrite/numericSlugs.php b/tests/phpunit/tests/rewrite/numericSlugs.php
index e11c6b2a46..41ef636368 100644
--- a/tests/phpunit/tests/rewrite/numericSlugs.php
+++ b/tests/phpunit/tests/rewrite/numericSlugs.php
@@ -23,7 +23,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '',
 				'post_name'    => '2015',
 				'post_date'    => '2015-02-01 01:00:00',
@@ -53,7 +53,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '',
 				'post_name'    => '2015',
 				'post_date'    => '2015-02-01 01:00:00',
@@ -80,7 +80,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '2015',
 				'post_date'    => '2015-02-01 01:00:00',
 			)
@@ -98,7 +98,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '2015',
 				'post_date'    => '2015-02-01 01:00:00',
 			)
@@ -114,7 +114,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '',
 				'post_name'    => '02',
 				'post_date'    => '2015-02-01 01:00:00',
@@ -133,7 +133,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '',
 				'post_name'    => '02',
 				'post_date'    => '2015-02-01 01:00:00',
@@ -150,7 +150,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '',
 				'post_name'    => '2',
 				'post_date'    => '2015-02-01 01:00:00',
@@ -169,7 +169,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '',
 				'post_name'    => '2',
 				'post_date'    => '2015-02-01 01:00:00',
@@ -186,7 +186,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '02',
 				'post_date'    => '2015-02-01 01:00:00',
 			)
@@ -204,7 +204,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '02',
 				'post_date'    => '2015-02-01 01:00:00',
 			)
@@ -220,7 +220,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '2',
 				'post_date'    => '2015-02-01 01:00:00',
 			)
@@ -238,7 +238,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '2',
 				'post_date'    => '2015-02-01 01:00:00',
 			)
@@ -254,7 +254,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '',
 				'post_name'    => '01',
 				'post_date'    => '2015-02-01 01:00:00',
@@ -273,7 +273,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '',
 				'post_name'    => '01',
 				'post_date'    => '2015-02-01 01:00:00',
@@ -290,7 +290,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '01',
 				'post_date'    => '2015-02-01 01:00:00',
 			)
@@ -308,7 +308,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '01',
 				'post_date'    => '2015-02-01 01:00:00',
 			)
@@ -324,7 +324,7 @@ class Tests_Rewrite_NumericSlugs extends WP_UnitTestCase {
 			array(
 				'post_author'  => $this->author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
+				'post_content' => 'content',
 				'post_title'   => '01',
 				'post_date'    => '2015-02-01 01:00:00',
 			)
diff --git a/tests/phpunit/tests/taxonomy.php b/tests/phpunit/tests/taxonomy.php
index 6d7cc06602..122f55b6bc 100644
--- a/tests/phpunit/tests/taxonomy.php
+++ b/tests/phpunit/tests/taxonomy.php
@@ -17,7 +17,7 @@ class Tests_Taxonomy extends WP_UnitTestCase {
 	 */
 	public function test_get_unknown_taxonomies() {
 		// Taxonomies for an unknown object type.
-		$this->assertSame( array(), get_object_taxonomies( rand_str() ) );
+		$this->assertSame( array(), get_object_taxonomies( 'unknown' ) );
 		$this->assertSame( array(), get_object_taxonomies( '' ) );
 		$this->assertSame( array(), get_object_taxonomies( 0 ) );
 		$this->assertSame( array(), get_object_taxonomies( null ) );
@@ -144,7 +144,7 @@ class Tests_Taxonomy extends WP_UnitTestCase {
 	public function test_register_taxonomy() {
 
 		// Make up a new taxonomy name, and ensure it's unused.
-		$tax = rand_str();
+		$tax = 'tax_new';
 		$this->assertFalse( taxonomy_exists( $tax ) );
 
 		register_taxonomy( $tax, 'post' );
@@ -158,7 +158,7 @@ class Tests_Taxonomy extends WP_UnitTestCase {
 	public function test_register_hierarchical_taxonomy() {
 
 		// Make up a new taxonomy name, and ensure it's unused.
-		$tax = rand_str();
+		$tax = 'tax_new';
 		$this->assertFalse( taxonomy_exists( $tax ) );
 
 		register_taxonomy( $tax, 'post', array( 'hierarchical' => true ) );
diff --git a/tests/phpunit/tests/term.php b/tests/phpunit/tests/term.php
index 61fbb3a397..737047bdd1 100644
--- a/tests/phpunit/tests/term.php
+++ b/tests/phpunit/tests/term.php
@@ -51,14 +51,17 @@ class Tests_Term extends WP_UnitTestCase {
 	 */
 	public function test_is_term_type() {
 		// Insert a term.
-		$term = rand_str();
+		$term = 'term_new';
 		$t    = wp_insert_term( $term, $this->taxonomy );
 		$this->assertIsArray( $t );
 		$term_obj = get_term_by( 'name', $term, $this->taxonomy );
-		$this->assertEquals( $t['term_id'], term_exists( $term_obj->slug ) );
 
+		$exists = term_exists( $term_obj->slug );
 		// Clean up.
-		$this->assertTrue( wp_delete_term( $t['term_id'], $this->taxonomy ) );
+		$deleted = wp_delete_term( $t['term_id'], $this->taxonomy );
+
+		$this->assertEquals( $t['term_id'], $exists );
+		$this->assertTrue( $deleted );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/term/getTermField.php b/tests/phpunit/tests/term/getTermField.php
index a5a132a9b4..c69044564c 100644
--- a/tests/phpunit/tests/term/getTermField.php
+++ b/tests/phpunit/tests/term/getTermField.php
@@ -91,7 +91,7 @@ class Tests_Term_getTermField extends WP_UnitTestCase {
 	}
 
 	public function test_get_term_field_name() {
-		$name = rand_str( 15 );
+		$name = 'baz';
 
 		$term = self::factory()->term->create_and_get(
 			array(
@@ -106,7 +106,7 @@ class Tests_Term_getTermField extends WP_UnitTestCase {
 	}
 
 	public function test_get_term_field_slug_when_slug_is_set() {
-		$slug = rand_str( 15 );
+		$slug = 'baz';
 
 		$term = self::factory()->term->create_and_get(
 			array(
@@ -121,7 +121,7 @@ class Tests_Term_getTermField extends WP_UnitTestCase {
 	}
 
 	public function test_get_term_field_slug_when_slug_falls_back_from_name() {
-		$name = rand_str( 15 );
+		$name = 'baz';
 
 		$term = self::factory()->term->create_and_get(
 			array(
@@ -156,7 +156,7 @@ class Tests_Term_getTermField extends WP_UnitTestCase {
 	}
 
 	public function test_get_term_field_description() {
-		$desc = wpautop( rand_str() );
+		$desc = wpautop( 'baz' );
 
 		$term = self::factory()->term->create_and_get(
 			array(
diff --git a/tests/phpunit/tests/term/splitSharedTerm.php b/tests/phpunit/tests/term/splitSharedTerm.php
index 65cefe8c4a..52e4281016 100644
--- a/tests/phpunit/tests/term/splitSharedTerm.php
+++ b/tests/phpunit/tests/term/splitSharedTerm.php
@@ -208,7 +208,7 @@ class Tests_Term_SplitSharedTerm extends WP_UnitTestCase {
 			array( '%d' )
 		);
 
-		$menu_id       = wp_create_nav_menu( rand_str() );
+		$menu_id       = wp_create_nav_menu( 'Nav Menu Bar' );
 		$cat_menu_item = wp_update_nav_menu_item(
 			$menu_id,
 			0,
diff --git a/tests/phpunit/tests/term/termExists.php b/tests/phpunit/tests/term/termExists.php
index bb4381036b..8bd9a783c7 100644
--- a/tests/phpunit/tests/term/termExists.php
+++ b/tests/phpunit/tests/term/termExists.php
@@ -260,7 +260,7 @@ class Tests_TermExists extends WP_UnitTestCase {
 		register_taxonomy( 'wptests_tax', 'post' );
 
 		// Insert a term.
-		$term = rand_str();
+		$term = __FUNCTION__;
 		$t    = wp_insert_term( $term, 'wptests_tax' );
 		$this->assertIsArray( $t );
 		$this->assertEquals( $t['term_id'], term_exists( $t['term_id'] ) );
diff --git a/tests/phpunit/tests/term/wpSetObjectTerms.php b/tests/phpunit/tests/term/wpSetObjectTerms.php
index b0da2fa3d6..8032a50e79 100644
--- a/tests/phpunit/tests/term/wpSetObjectTerms.php
+++ b/tests/phpunit/tests/term/wpSetObjectTerms.php
@@ -133,9 +133,9 @@ class Tests_Term_WpSetObjectTerms extends WP_UnitTestCase {
 		$ids = self::$post_ids;
 
 		$terms = array(
-			rand_str(),
-			rand_str(),
-			rand_str(),
+			'term0',
+			'term1',
+			'term2',
 		);
 
 		foreach ( $ids as $id ) {
@@ -164,7 +164,7 @@ class Tests_Term_WpSetObjectTerms extends WP_UnitTestCase {
 
 	public function test_set_object_terms_invalid() {
 		// Bogus taxonomy.
-		$result = wp_set_object_terms( self::$post_ids[0], array( rand_str() ), rand_str() );
+		$result = wp_set_object_terms( self::$post_ids[0], array( 'foo' ), 'invalid-taxonomy' );
 		$this->assertWPError( $result );
 	}
 
diff --git a/tests/phpunit/tests/term/wpTaxonomy.php b/tests/phpunit/tests/term/wpTaxonomy.php
index a8689284c2..a47edcc9ee 100644
--- a/tests/phpunit/tests/term/wpTaxonomy.php
+++ b/tests/phpunit/tests/term/wpTaxonomy.php
@@ -18,7 +18,7 @@ class Tests_WP_Taxonomy extends WP_UnitTestCase {
 		/* @var WP $wp */
 		global $wp;
 
-		$taxonomy        = rand_str();
+		$taxonomy        = 'taxonomy1';
 		$taxonomy_object = new WP_Taxonomy( $taxonomy, 'post' );
 
 		$taxonomy_object->add_rewrite_rules();
@@ -31,7 +31,7 @@ class Tests_WP_Taxonomy extends WP_UnitTestCase {
 		/* @var WP $wp */
 		global $wp;
 
-		$taxonomy        = rand_str();
+		$taxonomy        = 'taxonomy2';
 		$taxonomy_object = new WP_Taxonomy(
 			$taxonomy,
 			'post',
@@ -58,7 +58,7 @@ class Tests_WP_Taxonomy extends WP_UnitTestCase {
 		/* @var WP_Rewrite $wp_rewrite */
 		global $wp_rewrite;
 
-		$taxonomy        = rand_str();
+		$taxonomy        = 'taxonomy3';
 		$taxonomy_object = new WP_Taxonomy(
 			$taxonomy,
 			'post',
@@ -79,7 +79,7 @@ class Tests_WP_Taxonomy extends WP_UnitTestCase {
 	}
 
 	public function test_adds_ajax_callback() {
-		$taxonomy        = rand_str();
+		$taxonomy        = 'taxonomy4';
 		$taxonomy_object = new WP_Taxonomy(
 			$taxonomy,
 			'post',
diff --git a/tests/phpunit/tests/theme.php b/tests/phpunit/tests/theme.php
index ce81c95bba..23e2efad73 100644
--- a/tests/phpunit/tests/theme.php
+++ b/tests/phpunit/tests/theme.php
@@ -299,7 +299,7 @@ class Tests_Theme extends WP_UnitTestCase {
 				// get_query_template()
 
 				// Template file that doesn't exist.
-				$this->assertSame( '', get_query_template( rand_str() ) );
+				$this->assertSame( '', get_query_template( 'nonexistant' ) );
 
 				// Template files that do exist.
 				/*
@@ -333,8 +333,8 @@ class Tests_Theme extends WP_UnitTestCase {
 
 	public function test_switch_theme_bogus() {
 		// Try switching to a theme that doesn't exist.
-		$template = rand_str();
-		$style    = rand_str();
+		$template = 'some_template';
+		$style    = 'some_style';
 		update_option( 'template', $template );
 		update_option( 'stylesheet', $style );
 
diff --git a/tests/phpunit/tests/user.php b/tests/phpunit/tests/user.php
index c3930724ae..8c4c0d199e 100644
--- a/tests/phpunit/tests/user.php
+++ b/tests/phpunit/tests/user.php
@@ -104,7 +104,7 @@ class Tests_User extends WP_UnitTestCase {
 		$this->assertSame( $val, get_user_option( $key, self::$author_id ) );
 
 		// Change and get again.
-		$val2 = rand_str();
+		$val2 = 'baz';
 		update_user_option( self::$author_id, $key, $val2 );
 		$this->assertSame( $val2, get_user_option( $key, self::$author_id ) );
 	}
@@ -135,7 +135,7 @@ class Tests_User extends WP_UnitTestCase {
 		// Delete by key AND value.
 		update_user_meta( self::$author_id, $key, $val );
 		// Incorrect key: key still exists.
-		delete_user_meta( self::$author_id, $key, rand_str() );
+		delete_user_meta( self::$author_id, $key, 'foo' );
 		$this->assertSame( $val, get_user_meta( self::$author_id, $key, true ) );
 		// Correct key: deleted.
 		delete_user_meta( self::$author_id, $key, $val );
@@ -149,9 +149,9 @@ class Tests_User extends WP_UnitTestCase {
 	public function test_usermeta_array() {
 		// Some values to set.
 		$vals = array(
-			rand_str() => 'val-' . rand_str(),
-			rand_str() => 'val-' . rand_str(),
-			rand_str() => 'val-' . rand_str(),
+			'key0' => 'val0',
+			'key1' => 'val1',
+			'key2' => 'val2',
 		);
 
 		// There is already some stuff in the array.
@@ -475,8 +475,8 @@ class Tests_User extends WP_UnitTestCase {
 		$post = array(
 			'post_author'  => self::$author_id,
 			'post_status'  => 'publish',
-			'post_content' => rand_str(),
-			'post_title'   => rand_str(),
+			'post_content' => 'content',
+			'post_title'   => 'title',
 			'post_type'    => 'post',
 		);
 
@@ -636,7 +636,7 @@ class Tests_User extends WP_UnitTestCase {
 	public function test_user_meta_error() {
 		$id1 = wp_insert_user(
 			array(
-				'user_login' => rand_str(),
+				'user_login' => 'taco_burrito',
 				'user_pass'  => 'password',
 				'user_email' => 'taco@burrito.com',
 			)
@@ -645,7 +645,7 @@ class Tests_User extends WP_UnitTestCase {
 
 		$id2 = wp_insert_user(
 			array(
-				'user_login' => rand_str(),
+				'user_login' => 'taco_burrito2',
 				'user_pass'  => 'password',
 				'user_email' => 'taco@burrito.com',
 			)
@@ -826,9 +826,9 @@ class Tests_User extends WP_UnitTestCase {
 	 */
 	public function test_wp_insert_user_should_not_wipe_existing_password() {
 		$user_details = array(
-			'user_login' => rand_str(),
+			'user_login' => 'jonsnow',
 			'user_pass'  => 'password',
-			'user_email' => rand_str() . '@example.com',
+			'user_email' => 'jonsnow@example.com',
 		);
 
 		$user_id = wp_insert_user( $user_details );
diff --git a/tests/phpunit/tests/user/author.php b/tests/phpunit/tests/user/author.php
index 5786578855..1a624ec833 100644
--- a/tests/phpunit/tests/user/author.php
+++ b/tests/phpunit/tests/user/author.php
@@ -26,8 +26,8 @@ class Tests_User_Author_Template extends WP_UnitTestCase {
 			array(
 				'post_author'  => self::$author_id,
 				'post_status'  => 'publish',
-				'post_content' => rand_str(),
-				'post_title'   => rand_str(),
+				'post_content' => 'content',
+				'post_title'   => 'title',
 				'post_type'    => 'post',
 			)
 		);
diff --git a/tests/phpunit/tests/xmlrpc/wp/editProfile.php b/tests/phpunit/tests/xmlrpc/wp/editProfile.php
index 7c00626908..2789dbe460 100644
--- a/tests/phpunit/tests/xmlrpc/wp/editProfile.php
+++ b/tests/phpunit/tests/xmlrpc/wp/editProfile.php
@@ -16,13 +16,13 @@ class Tests_XMLRPC_wp_editProfile extends WP_XMLRPC_UnitTestCase {
 		$subscriber_id = $this->make_user_by_role( 'subscriber' );
 
 		$new_data = array(
-			'first_name'   => rand_str(),
-			'last_name'    => rand_str(),
+			'first_name'   => 'firstname',
+			'last_name'    => 'lastname',
 			'url'          => 'http://www.example.org/subscriber',
-			'display_name' => rand_str(),
-			'nickname'     => rand_str(),
-			'nicename'     => rand_str(),
-			'bio'          => rand_str( 200 ),
+			'display_name' => 'displayname',
+			'nickname'     => 'nickname',
+			'nicename'     => 'nicename',
+			'bio'          => 'Lorem ipsum dolor sit amet, consectetur adipiscing elit.',
 		);
 		$result   = $this->myxmlrpcserver->wp_editProfile( array( 1, 'subscriber', 'subscriber', $new_data ) );
 		$this->assertNotIXRError( $result );
diff --git a/tests/phpunit/tests/xmlrpc/wp/getComment.php b/tests/phpunit/tests/xmlrpc/wp/getComment.php
index e43a733910..08cd4a5b00 100644
--- a/tests/phpunit/tests/xmlrpc/wp/getComment.php
+++ b/tests/phpunit/tests/xmlrpc/wp/getComment.php
@@ -18,7 +18,7 @@ class Tests_XMLRPC_wp_getComment extends WP_XMLRPC_UnitTestCase {
 			'comment_author'       => 'Test commenter',
 			'comment_author_url'   => 'http://example.com/',
 			'comment_author_email' => 'example@example.com',
-			'comment_content'      => rand_str( 100 ),
+			'comment_content'      => 'Lorem ipsum dolor sit amet, consectetur adipiscing elit.',
 		);
 		self::$parent_comment_id   = wp_insert_comment( self::$parent_comment_data );
 
@@ -28,7 +28,7 @@ class Tests_XMLRPC_wp_getComment extends WP_XMLRPC_UnitTestCase {
 			'comment_author_url'   => 'http://example.org/',
 			'comment_author_email' => 'example@example.org',
 			'comment_parent'       => self::$parent_comment_id,
-			'comment_content'      => rand_str( 100 ),
+			'comment_content'      => 'Duis non neque cursus, commodo massa in, bibendum nisl.',
 		);
 		self::$child_comment_id   = wp_insert_comment( self::$child_comment_data );
 	}
diff --git a/tests/phpunit/tests/xmlrpc/wp/getPost.php b/tests/phpunit/tests/xmlrpc/wp/getPost.php
index 0fd81ada8a..be25ca2770 100644
--- a/tests/phpunit/tests/xmlrpc/wp/getPost.php
+++ b/tests/phpunit/tests/xmlrpc/wp/getPost.php
@@ -14,9 +14,9 @@ class Tests_XMLRPC_wp_getPost extends WP_XMLRPC_UnitTestCase {
 
 		$this->post_date_ts            = strtotime( '+1 day' );
 		$this->post_data               = array(
-			'post_title'   => rand_str(),
-			'post_content' => rand_str( 2000 ),
-			'post_excerpt' => rand_str( 100 ),
+			'post_title'   => 'Post Title',
+			'post_content' => 'Lorem ipsum dolor sit amet, consectetur adipiscing elit.',
+			'post_excerpt' => 'Post Excerpt',
 			'post_author'  => $this->make_user_by_role( 'author' ),
 			'post_date'    => date_format( date_create( "@{$this->post_date_ts}" ), 'Y-m-d H:i:s' ),
 		);
diff --git a/tests/phpunit/tests/xmlrpc/wp/newComment.php b/tests/phpunit/tests/xmlrpc/wp/newComment.php
index 6cc6c30160..7c2eacc6b1 100644
--- a/tests/phpunit/tests/xmlrpc/wp/newComment.php
+++ b/tests/phpunit/tests/xmlrpc/wp/newComment.php
@@ -55,7 +55,7 @@ class Tests_XMLRPC_wp_newComment extends WP_XMLRPC_UnitTestCase {
 				'administrator',
 				self::$posts['publish']->ID,
 				array(
-					'content' => rand_str( 100 ),
+					'content' => 'Content',
 				),
 			)
 		);
@@ -155,7 +155,7 @@ class Tests_XMLRPC_wp_newComment extends WP_XMLRPC_UnitTestCase {
 				'administrator',
 				$post->ID,
 				array(
-					'content' => rand_str( 100 ),
+					'content' => 'Content',
 				),
 			)
 		);
@@ -171,7 +171,7 @@ class Tests_XMLRPC_wp_newComment extends WP_XMLRPC_UnitTestCase {
 			'administrator',
 			self::$posts['publish']->ID,
 			array(
-				'content' => rand_str( 100 ),
+				'content' => 'Content',
 			),
 		);