[tests] Normalize casing of command identifiers in constraint.

We do not care much about the casing of command IDs in our constraint,
so it makes no difference for use if it is "SET" or "set".

tests/PHPUnit/RedisCommandConstraint.php

@@ -25,10 +25,10 @@ class RedisCommandConstraint extends PHPUnit_Framework_Constraint
     public function __construct($command = null, array $arguments = null)
     {
         if ($command instanceof CommandInterface) {
-            $this->commandID = $command->getId();
+            $this->commandID = strtoupper($command->getId());
             $this->arguments = $arguments ?: $commant->getArguments();
         } else {
-            $this->commandID = $command;
+            $this->commandID = strtoupper($command);
             $this->arguments = $arguments;
         }
     }
@@ -42,7 +42,7 @@ class RedisCommandConstraint extends PHPUnit_Framework_Constraint
             return false;
         }
 
-        if ($this->commandID && $other->getId() !== $this->commandID) {
+        if ($this->commandID && strtoupper($other->getId()) !== $this->commandID) {
             return false;
         }
 
@@ -74,7 +74,7 @@ class RedisCommandConstraint extends PHPUnit_Framework_Constraint
         $string = 'is a Redis command';
 
         if ($this->commandID) {
-            $string .= " with ID `{$this->commandID}";
+            $string .= " with ID '{$this->commandID}'";
         }
 
         if ($this->arguments) {