tests: Guard against Flex presence (#162)

If the Flex plugin is installed on the machine, running tests locally
will cause additional noise.

e2e/scenario0/vendor-bin/ns1/composer.json

@@ -1 +1,2 @@
-{}
+{
+}

e2e/scenario0/vendor-bin/ns2/composer.json

@@ -1 +1,2 @@
-{}
+{
+}

e2e/scenario1/vendor-bin/ns1/composer.json

@@ -1 +1,2 @@
-{}
+{
+}

e2e/scenario1/vendor-bin/ns2/composer.json

@@ -1 +1,2 @@
-{}
+{
+}

e2e/scenario11/vendor-bin/ns1/composer.json

@@ -1 +1,2 @@
-{}
+{
+}

e2e/scenario3/vendor-bin/ns1/composer.json

@@ -1 +1,2 @@
-{}
+{
+}

e2e/scenario8/vendor-bin/ns1/composer.json

@@ -1 +1,2 @@
-{}
+{
+}

tests/EndToEndTest.php

@@ -56,11 +56,11 @@ public function test_it_passes_the_e2e_test(string $scenarioPath): void
 
         $actualPath = $scenarioPath.'/actual.txt';
 
-        if (file_exists($actualPath)) {
-            $originalContent = file_get_contents($scenarioPath.'/actual.txt');
-        } else {
-            $originalContent = 'File was not created.';
-        }
+        $originalContent = file_exists($actualPath)
+            ? self::removeFlexMessages(
+                file_get_contents($scenarioPath . '/actual.txt')
+            )
+            : 'File was not created.';
 
         $errorMessage = <<<TXT
 Standard output:
@@ -187,4 +187,17 @@ private static function normalizeTrailingWhitespacesAndLineReturns(string $value
             array_map('rtrim', explode(PHP_EOL, $value))
         );
     }
+
+    private static function removeFlexMessages(string $value): string
+    {
+        return preg_replace(
+            '/.+Symfony\\\\Flex.+\n/',
+            '',
+            str_replace(
+                "Symfony recipes are disabled: \"symfony/flex\" not found in the root composer.json\n\n",
+                '',
+                $value
+            )
+        );
+    }
 }