minor #21650 [Yaml] add tests for specific mapping keys (xabbuh)

This PR was merged into the 2.7 branch.

Discussion
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[Yaml] add tests for specific mapping keys

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | see symfony/symfony#21643 (comment)
| License       | MIT
| Doc PR        |

Commits
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b8e0d705f6 [Yaml] add tests for specific mapping keys

Author: fabpot

Tests/InlineTest.php

@@ -421,4 +421,15 @@ public function testVeryLongQuotedStrings()
 
         $this->assertEquals($longStringWithQuotes, $arrayFromYaml['longStringWithQuotes']);
     }
+
+    public function testBooleanMappingKeysAreConvertedToStrings()
+    {
+        $this->assertSame(array('false' => 'foo'), Inline::parse('{false: foo}'));
+        $this->assertSame(array('true' => 'foo'), Inline::parse('{true: foo}'));
+    }
+
+    public function testTheEmptyStringIsAValidMappingKey()
+    {
+        $this->assertSame(array('' => 'foo'), Inline::parse('{ "": foo }'));
+    }
 }