diff --git a/tests/AbstractTest.php b/tests/AbstractTest.php
index 3133f0b..7c7c7a0 100644
--- a/tests/AbstractTest.php
+++ b/tests/AbstractTest.php
@@ -17,7 +17,7 @@ abstract class AbstractTest extends TestCase
     /**
      * @inheritDoc
      */
-    protected function setUp()
+    protected function setUp(): void
     {
         $filesystem = new Filesystem();
         $filesystem->chmod($this->getSandboxRoot(), 0777, umask(), true);
diff --git a/tests/CommandSimulationTest.php b/tests/CommandSimulationTest.php
index 338a0c2..b0ce93a 100644
--- a/tests/CommandSimulationTest.php
+++ b/tests/CommandSimulationTest.php
@@ -64,10 +64,10 @@ public function testSimulation($command, array $config, $composer, array $expect
 
         $text = $output->fetch();
         foreach ($expected as $row) {
-            $this->assertContains($row, $text);
+            $this->assertStringContainsString($row, $text);
         }
         foreach ($absent as $row) {
-            $this->assertNotContains($row, $text);
+            $this->assertStringNotContainsString($row, $text);
         }
     }