Expanded InstallerTest to support expecting Exceptions by supplying "EXCEPTION" as "--EXPECT--"

tests/Composer/Test/InstallerTest.php

@@ -158,6 +158,8 @@ class InstallerTest extends TestCase
             ->method('writeError')
             ->will($this->returnCallback($callback));
 
+        // Prepare for exceptions
+        try {
             $composer = FactoryMock::create($io, $composerConfig);
 
             $jsonMock = $this->getMockBuilder('Composer\Json\JsonFile')->disableOriginalConstructor()->getMock();
@@ -249,6 +251,17 @@ class InstallerTest extends TestCase
                 $this->assertEquals(rtrim($expectOutput), rtrim($output));
             }
         }
+        catch(\Exception $e) {
+            // Exception was thrown during execution
+            if (!$expect || !$expectOutput) {
+                throw $e;
+            }
+            $this->assertEquals('EXCEPTION', rtrim($expect));
+            $normalizedOutput = rtrim(str_replace("\n", PHP_EOL, $expectOutput));
+            $this->assertEquals($normalizedOutput, rtrim($e->getMessage()));
+        }
+        return;
+    }
 
     public function getIntegrationTests()
     {