test: fix tests

Author: adhocore

tests/Helper/ShellTest.php

@@ -82,11 +82,12 @@ public function test_error_output()
         $shell = new Shell('false');
 
         $this->assertSame(1, $shell->execute()->getExitCode());
+        $this->assertSame('', $shell->execute()->getErrorOutput());
     }
 
     public function test_exitcode()
     {
-        $shell = new Shell('php -v');
+        $shell = new Shell('true');
 
         $this->assertSame(0, $shell->execute()->getExitCode());
     }

tests/Input/CommandTest.php

@@ -237,8 +237,6 @@ public function test_args()
     public function test_tap()
     {
         $this->assertInstanceOf(static::class, $this->newCommand()->tap($this));
-        $this->assertSame('asdf', $this->newCommand()->tap('asdf'));
-        $this->assertSame(234, $this->newCommand()->tap(234));
     }
 
     public function test_app_tap()