diff --git a/src/Expectation.php b/src/Expectation.php
index 3bdce69..c93d96b 100644
--- a/src/Expectation.php
+++ b/src/Expectation.php
@@ -12,7 +12,7 @@ public function toReturnLowercase(int $depth = -1): void
     {
         $this->applyOnDirectory(
             $depth,
-            fn (array $content): array => $this->lowercasesIn($content),
+            fn (array $content): array => $this->notLowercasesIn($content),
             'Not lowercase detected'
         );
     }
@@ -30,7 +30,7 @@ public function toReturnSingleWords(int $depth = -1): void
     {
         $this->applyOnDirectory(
             $depth,
-            fn (array $content): array => $this->singleWordsIn($content),
+            fn (array $content): array => $this->multipleWordsIn($content),
             'Not single words detected'
         );
     }
diff --git a/src/Investigator.php b/src/Investigator.php
index 483dd61..c0e115b 100644
--- a/src/Investigator.php
+++ b/src/Investigator.php
@@ -4,13 +4,16 @@
 
 namespace Faissaloux\PestInside;
 
+/**
+ * @internal
+ */
 trait Investigator
 {
     /**
      * @param  array<string|array<string>>  $array
      * @return array<string>
      */
-    private function lowercasesIn(array $array): array
+    private function notLowercasesIn(array $array): array
     {
         $unwanted = [];
 
@@ -20,7 +23,7 @@ private function lowercasesIn(array $array): array
             }
 
             if (is_array($word)) {
-                array_push($unwanted, ...$this->lowercasesIn($word));
+                array_push($unwanted, ...$this->notLowercasesIn($word));
 
                 continue;
             }
@@ -63,13 +66,13 @@ private function duplicatesIn(array $array): array
      * @param  array<string|array<string>>  $array
      * @return array<string>
      */
-    private function singleWordsIn(array $array): array
+    private function multipleWordsIn(array $array): array
     {
         $unwanted = [];
 
         foreach ($array as $word) {
             if (is_array($word)) {
-                array_push($unwanted, ...$this->singleWordsIn($word));
+                array_push($unwanted, ...$this->multipleWordsIn($word));
 
                 continue;
             }