minor #13755 [Console] assertion for ArgvInput::getFirstArgument() with no arguments (nanocom)

This PR was merged into the 2.3 branch.

Discussion
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[Console] assertion for ArgvInput::getFirstArgument() with no arguments

| Q             | A
| ------------- | ---
| Bug fix?      | [no]
| New feature?  | [no]
| BC breaks?    | [no]
| Deprecations? | [no]
| Tests pass?   | [yes]
| License       | MIT

Commits
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11b2a9b [Console] explicit assertion for ArgvInput::getFirstArgument() with no arguments

Author: fabpot

src/Symfony/Component/Console/Tests/Input/ArgvInputTest.php

@@ -257,7 +257,7 @@ public function testParseEmptyStringArgument()
     public function testGetFirstArgument()
     {
         $input = new ArgvInput(array('cli.php', '-fbbar'));
-        $this->assertEquals('', $input->getFirstArgument(), '->getFirstArgument() returns the first argument from the raw input');
+        $this->assertNull($input->getFirstArgument(), '->getFirstArgument() returns null when there is no arguments');
 
         $input = new ArgvInput(array('cli.php', '-fbbar', 'foo'));
         $this->assertEquals('foo', $input->getFirstArgument(), '->getFirstArgument() returns the first argument from the raw input');